8123-111462-02 DEEP BRAIN STIMULATION OF PULVINAR OR SUPERIOR COLLICULUS NUCLEI TO TREAT MEDICALLY INTRACTABLE EPILEPSY CROSS REFERENCE TO RELATED APPLICATION This application claims priority to U.S. Provisional Application No.63/644,864, filed May 9, 2024, which is incorporated by reference in its entirety. FIELD [0001] The present disclosure relates to neurostimulation for the treatment of epilepsy, such as medically refractory focal epilepsy, in a subject. BACKGROUND [0002] Epilepsy is one of the most common brain disorders, characterized by chronically recurrent seizures resulting from excessive electrical discharges from groups of neurons. Epilepsy affects about 50 million people worldwide. About 40% of epilepsy patients have medically refractory epilepsy, which cannot be controlled by non-invasive medical therapy such as anti-epilepsy drugs. Medically refractory epilepsy is a debilitating illness where individuals lose their independence, causing profound behavioral, psychological, social, financial and legal issues. [0003] For medically refractory epilepsy patients with focal epilepsy, the current standard of care is to resect the epileptogenic zone, which is the minimal area of brain tissue responsible for generating the recurrent seizure activity. However, this treatment is generally only recommended if the cortical area containing the epileptogenic zone is amenable for safe removal. In patients with focal epilepsy involving highly eloquent cortical areas such as the posterior quadrant the risk of devastating neurological consequences as vision deficits, minimizes resection options. SUMMARY [0004] Provided herein are methods for treating epilepsy in a subject. In some examples, the methods treat focal epilepsy in the subject, such as focal posterior quadrant epilepsy. In some examples, the methods treat generalized epilepsy in the subject. The methods comprise applying a therapeutically effective amount of an electrical stimulus to pulvinar and/or superior colliculus neurons with one or more electrodes of a deep brain stimulator implanted in the pulvinar and/or superior colliculus of the subject and controlled by a neurostimulator.
8123-111462-02 In several implementations, the pulvinar and/or superior colliculus neurons include projections to a target location in the posterior quadrant cortex of the subject that comprises an epileptogenic zone for seizure-induced impairment in the subject. The electrical stimulus is applied in an amount sufficient to inhibit epileptiform activity in the epileptogenic zone and reduce the seizure-induced impairment. In several implementations the electrical stimulus comprises electrical pulses having a pulse frequency of at least 100 Hz, such as between 100 Hz and about 1000 Hz, or between about 150 Hz and about 200 Hz. [0005] In some implementations, the electrical stimulus is applied to neurons in a particular pulvinar nucleus, such as the medial nucleus, the lateral nucleus, or the inferior nucleus, of the pulvinar, or the pulvinar/superior colliculus transition. [0006] In some implementations, the neurostimulator is activated to apply the electrical stimulus in response to feedback (such as epileptiform activity indicating the presence or onset of a seizure) in the subject from one or more electrodes for sensing seizure activity at the target location in the subject. In some implementations, the neurostimulator is configured for activation by the subject in response to sensation of an aura of the focal epilepsy. [0007] Provided herein are methods that include applying an electrical stimulus with one or more electrodes to the neurons located in the pulvinar nuclei of the thalamus an amount sufficient reduce the seizure-induced impairment in the subject. In particular implementations, the electrical stimulus includes electrical pulses with an amplitude of less than about 10 mA, pulse widths between about 100 µs and about 2 ms, and/or a pulse frequency between about 100 Hz and about 1000 Hz. In particular examples, the electrical pulses include charge-balanced pulses. In these and further implementations, the electrical stimulus may be a continuous electrical stimulus, or else may be a closed-loop electrical stimulus. [0008] In methods according to some implementations herein, an electrical stimulus is applied by one or more electrodes controlled by a neurostimulator. In some implementations, the neurostimulator is externalized with respect to the human subject. In further implementations, the neurostimulator is implanted in the human subject. For example, in specific implementations, the neurostimulator is fully implanted in the brain of the subject. In further implementations, the neurostimulator is implanted in the chest of the subject. In still further implementations, the neurostimulator is implanted in the belly of the subject. [0009] In some implementations, a neurostimulator utilized in methods herein is a current or voltage-controlled stimulator. In particular implementations, the neurostimulator controls the application of an electrical stimulus in a phasic manner. For example, the stimulation
8123-111462-02 parameters of the neurostimulator may change over the course of a detected seizure. In some implementations herein, the neurostimulator comprises at least one multiple contact lead that is configured to produce orientation-selective axonal stimulation. [0010] The foregoing and other objects, features, and advantages of the implementations will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES [0011] FIG.1. Pulvinar-cortical evoked potentials. Example of cortical evoked potential recorded from a posterior quadrant electrode (“EOZ:lingula”) and a non-posterior quadrant electrode, based on stimulation using a pulvinar-implanted electrode. In the graphs, the vertical gray line (time 0) indicates the time of pulvinar stimulation, with recording traces from the posterior quadrant electrode or non-posterior quadrant electrode shown. As shown, pulvinar nucleus shows preferential structural connectivity with posterior quadrant regions. [0012] FIG.2A and 2B. Pulvinar correlation with epileptogenic zone during seizures. FIG.2A: example of neural trace from the epileptogenic zone in the posterior quadrant during a seizure, the pulvinar, and the correlation among these regions. Example 2B: boxplot showing the mean correlation coefficient of pulvinar and epileptogenic zone for multiple seizures. [0013] FIG.3. Pulvinar stimulation reduces epileptogenic activity. Example of interictal spikes reductions in rate and amplitude with high frequency pulvinar stimulation. [0014] FIGs.4A-4F: Study design and patient demographics. (FIG.4A) Left: Schematic of hodological matching of PUL, ANT and VIM/VOP to specific cortical anatomical regions. Right: anatomical localization of PUL, ANT and VIM/VOP nuclei on MNI space average T1-weighted MRI with axial view and magnification of the thalamic nuclei. Thalamic parcellation is atlas-guided (A=anterior, P=posterior, M=medial, L=lateral). (FIG.4B) Top right: axial view of reconstruction of stereoelectroencephalography (SEEG) electrodes targeting thalamic nuclei of interest. Top left: magnification of the contacts located in the PUL, ANT, and VIM/VOP. Bottom: side and top view of the left and right hemisphere SEEG thalamic implantations. (FIG.4C) Stratification of SEEG patients (S01-S26). Top Left: pie chart of the lobar location of the SOZ. Top Right: pie chart of 37 thalamic SEEG contacts in PUL, ANT and VIM/VOP. A higher number of thalamic contacts than patients implies that some patients had more than one nucleus of interest implanted. Bottom: Stratification of the 216 recorded spontaneous seizures according to the lobar location of different SOZs (left)
8123-111462-02 and the respective thalamic coverage (right). A different distribution from the top panel implies a different number of seizures for each patient, as reported in Table 2. (FIG.4D) Top: Stratification of 7 chronically implanted patients (S16, S27-32) according to the lobar location of the SOZ (left) and implanted thalamic nucleus (right). (FIG.4E) histogram of follow-up years of chronically implanted patients. (FIG.4F) Design and experiments of the study. Patients received SEEG implantation and were stratified according to their SOZ and thalamic coverage. Bottom, left to right: the anatomical (imaging and electrophysiology), and functional coupling during seizures involving the thalamus, hence defining hodologically matching and unmatching nuclei. the effect of acute thalamic stimulation and finally the clinical outcome following chronic thalamic stimulation was tested. [0015] FIGs.5A-5L: Anatomical connectivity of PUL, ANT and VIM/VOP via neuroimaging and electrophysiology. (FIG.5A) Representative example of high-definition fiber tracking (HDFT) from PUL, ANT and VIM/VOP nuclei (S01). (FIG.5B) Volume of thalamocortical projections (mean ± standard error, n= 8 patients) from each nucleus to each cortical lobe normalized by the total volume of fibers projecting from each nucleus (mean ± standard error). (FIG.5C) Group-level analysis of thalamocortical EPs. For each patient, the mean peak to peak amplitude is calculated across the contacts of a representative electrode for each cortical lobe. The normalized peak to peak amplitude of EP is shown according to the stimulating nucleus evoking the response. (FIG.5D, 5G, 5J) Anatomical localization of SEEG implantation of representative patients (S01, S22, S13) that were tested for EPs with stimulation of PUL, ANT and VIM/VOP respectively. Each electrode is shown according to the brain lobe, and thalamic electrodes are indicated by an arrow. (FIG.5E, 5H, 5K) Raw traces of stimulation triggered averages in different brain lobes from PUL, ANT and VIM/VOP respectively. Specific anatomical regions are: frontal operculum (pars opercularis), supplementary motor area, angular gyrus, inferior temporal sulcus (panel e, left to right); superior frontal sulcus, motor cingulate, posterior cingulate, posterior uncus (panel h, left to right); anterior cingulate, supplementary motor area, precuneus (panel k, left to right); (FIG.5F, 5I, 5L) Violin plot of peak to peak amplitude of EPs in different brain lobes for PUL, ANT and VIM/VOP respectively. For all panels, statistical significance was assessed with two-tail bootstrapping with Bonferroni correction: p<0.05 (*), p<0.01 (**), p<0.001(***). [0016] FIGs.6A-6G: Functional coupling of the PUL, ANT and VIM/VOP nuclei with SOZ during seizures. (FIG.6A) Representative examples of thalamocortical connectivity profiles of PUL (right, S03), ANT (middle, S24) and VIM/VOP (left, S26) with matched
8123-111462-02 SOZ. For all nuclei, the top panel shows the cortical recording in the contacts of the SOZ, the middle panel shows the thalamic recording, and the bottom panel shows the h2 correlation coefficient. The gray shaded area includes the seizure duration (from onset to termination). (FIG.6B) Boxplot of the mean h2 correlation for each seizure in matched and unmatched thalami, compared to mean h2 correlation during a baseline epoch preceding the seizure. Three representative patients are shown (right: S01, matched PUL, unmatched ANT; middle: S22, matched ANT, unmatched PUL; left: S12, matched PUL, unmatched VIM/VOP). (FIG. 6C) Raw traces of h2 correlation coefficient (smoothed for visualization) for a representative seizure for each patient of panel b. The gray shaded area includes the seizure duration (from onset to termination). (FIG.6D) Schematic illustrating the hodologically matching (bold lines) and unmatching (dashed gray lines) thalamocortical connections. (FIG.6E) Violin plot showing the mean h2 coefficient across seizures for each matched (top) and unmatched (bottom) thalamus-SOZ pair. (FIG.6F) Box plot of mean h2 coefficient across seizures during initiation, middle and termination phase of each seizure. (FIG.6G) Percentage difference of the change in h2 coefficient during seizures between matched and unmatched nuclei, across different frequency bands of interest. For all boxplots, the whiskers extend to the maximum spread not considering outliers, central, top, and bottom lines represent median, 25th, and 75th percentile, respectively. For all panels, statistical significance was assessed with two-tail bootstrapping with Bonferroni correction: p<0.05 (*), p<0.01 (**), p<0.001(***). [0017] FIGs.7A-7F: Analysis of thalamocortical versus corticothalamic interactions during seizures. (FIG.7A) Representative seizure recording (S01). The bar indicates the full seizure duration, while the shaded gray regions show the initiation and termination epoch. On such windows, the GC coefficient matrix was calculated that illustrates connectivity from and to the thalamic nuclei to a matched SOZ. (FIG.7B) Pie charts illustrating the proportion of seizures with higher corticothalamic (SOZ→th, light gray) or thalamocortical (th→SOZ, dark gray) GC coefficient for the initiation (left) and termination (right) epoch. (FIG.7C) (Left) Plot of the evolution of corticothalamic and thalamocortical GC coefficients for 10 s epochs starting two minutes before a representative seizure. The arrows indicate the relative change of GC from initiation to termination. (Right) Quantification of the relative percentage change of GC coefficient from initiation to termination, for corticothalamic (light gray) and thalamocortical (dark gray) direction. (FIG.7D) Boxplot of the relative percentage change of GC coefficient from initiation to termination for all subjects. Each data point represents the mean value across all the seizures for each subject. (FIG.7E) Pie charts illustrating the proportion of seizures with higher corticothalamic (SOZ→th, light grey) or thalamocortical
8123-111462-02 (th→SOZ, dark grey) GC coefficient for the initiation (left) and termination (right) epoch, separated from the three nuclei of interest (PUL at left, ANT at middle, VIM/VOP at right). (FIG.7F) Boxplot of the relative percentage change of GC coefficient from initiation to termination for all the seizures separated for the matched thalamic nucleus investigated (PUL at left, ANT at middle, VIM/VOP at right). For PUL n=38 and n=36 seizures, for ANT n=14 and n=15 seizures, for VIM/VOP n=38 and n=35 seizures. For all boxplots, the whiskers extend to the maximum spread not considering outliers, central, top, and bottom lines represent median, 25th, and 75th percentile, respectively. Outliers were removed with quartile method. For all panels, statistical significance was assessed with two-tail bootstrapping with Bonferroni correction: p<0.05 (*), p<0.01 (**), p<0.001(***). [0018] FIGs.8A-8H: Hodologically-matched electrical stimulation of the thalamus better reduces pathological IEDs. (FIG.8A) Representative example of an interictal SEEG recording of a SOZ contact, with clearly visible IED (spikes) and their time-frequency representation exploited for automatic detection. (FIG.8B) (Left) boxplot for IED rate/minute in stimulation OFF (n=18) and stimulation ON (n=8) epochs of the PUL (matched nucleus). (Right) representative stim OFF (top) and stim ON epoch (bottom) with matched PUL stimulation shows immediate suppression of IED. (FIG.8C) Representative example, as in panel b, for matched ANT stimulation (n=7 and n=17 for stimulation OFF and ON, respectively). (FIG.8D) Representative example, as in panel b and c, for matched VIM/VOP stimulation (n=8 and n=21 for stimulation OFF and ON, respectively). (FIG.8E) Boxplot of representative examples of unmatched thalamic stimulation on IED rate for ANT (left, n=18 vs n=8 for stimulation OFF and ON, respectively), and VIM/VOP (right, n=19 vs n=41 for stimulation OFF and ON, respectively). (FIG.8F) Percentage change relative to baseline of the probability of IEDs suppression in matched and unmatched thalamic stimulation in two representative patients. (FIG.8G) All-subject analysis of the IED rate percentage variation to baseline with matched (left) and unmatched (right) stimulation. (FIG.8H) All-subject analysis of the percentage change relative to baseline of the probability of IEDs suppression in matched (left) and unmatched (right) stimulation. For all boxplots, the whiskers extend to the maximum spread not considering outliers, central, top, and bottom lines represent median, 25th, and 75th percentile, respectively. Outliers were removed with quartile method (see Methods). For all panels, statistical significance was assessed with two-tail bootstrapping with Bonferroni correction: p<0.05 (*), p<0.01 (**), p<0.001(***). [0019] FIGs.9A-9C: Hodologically-matched thalamic stimulation as a neuromodulation therapy in chronic epilepsy treatment. (FIGs.9A-9B) Bar plot and radar plot of the
8123-111462-02 percentage of seizure frequency reduction for S16, S27-S32, compared to the median seizure frequency reduction reported by the SANTE trial at 7 years follow up for frontal, temporal and other lobes. (FIG.9C) Scatter plot of the number of antiseizure medication for each patient prior and after the matched thalamic neurostimulation implant. Dashed lines indicate no change in the numbers of ASM. [0020] FIGs.10A-10D: CM nucleus connectivity for generalized epilepsy. (FIGs.10A- 10B): structural connectivity of the CM. (FIG.10A): representative example (S01) of fiber tracts of the CM. (FIG.0B): Volume of thalamocortical projections (mean ± standard error over 8 patients) from CM to each cortical lobe normalized by the total volume of fibers. (FIGs.10C-10D): functional connectivity of the CM in generalized epilepsy. (FIG.10C): mean h2 coefficient averaged across 24 seizures, for n=13 bipolar channels and the CM, PUL, ANT and VIM/VOP. (FIG.10D): example of h2 coefficient between the CM, ANT, PUL and VIM/VOP and an epileptogenic zone contact over the course of a seizure. For visualization, the h2 envelope to reduce noise is reported. [0021] FIGs.11A-11D. Thalamocortical synchronization with non-linear correlation coefficient. (FIGs.11A-11B) h2 correlation of thalamus and non-SOZ areas. (FIG.11A): representative example of the h2 coefficient during the course of a seizure of the PUL with a matched SOZ (blu) and a non-SOZ (black) cortical region in S03. (FIG.11B) Boxplot of the mean h2 coefficient between each nucleus and the mean of 3 non-SOZ contacts during seizures. (FIG.11C): analysis of h2 coefficient during multiple phases of the seizure (onset, middle and termination). One representative patient for each nucleus (PUL, ANT, VIM/VOP) is represented (n=13, n=3, n=28 seizures respectively). (FIG.11D) Violin plot of the mean h2 coefficient during the seizure for all matched (n=27 nuclei) and unmatched (n=7 nuclei) thalami-SOZ pairs, for different frequency bands. Each point represents the mean across all the seizures. DETAILED DESCRIPTION I. Introduction [0022] Methods as disclosed herein arise from the unexpected discovery that deep brain stimulation (e.g., continuous stimulation) of specific areas in the pulvinar lead to suppression of epileptiform activity in a posterior quadrant epileptogenic zone in a primate. As will be understood by those in the art, this finding has broad implications for the treatment of focal seizures in a subject.
8123-111462-02 [0023] Using available technology, therapeutic electrical stimuli may be administered to a subject by implanted electrodes under the control of an implanted or external neurostimulator. The electrodes and neurostimulator together comprise a system that may be provided to a subject as an assistive device to reduce epileptic symptoms, including onset, duration, and frequency of seizures. This system may alternatively be used in combination with anti-epileptic drugs as known in the art for treatment of epilepsy. [0024] As shown in the Examples, methods according to disclosed implementations reduce cortical activity and epileptiform activity in the epileptogenic zone and provide, an alternative to epileptogenic zone resection for treatment epilepsy, including of focal or generalized epilepsy. II. Summary of Terms [0025] Unless otherwise noted, technical terms are used according to conventional usage. As used herein, the term “comprises” means “includes.” Although many methods and materials similar or equivalent to those described herein can be used, particular suitable methods and materials are described below. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting. The scope of the claims should not be limited to those features exemplified. To facilitate review of the various implementations, the following explanations of terms are provided: [0026] About: As used herein, the term “about” refers to an approximation of a qualitative or quantitative measurement. Whether the measurement is qualitative or quantitative should be clear from its context. With regard to quantitative measurements, “about” refers to plus or minus 5% of a reference value. For example, “about” 100mA refers to 95mA to 105mA. [0027] Closed-loop: A stimulation mechanism wherein a sensor continuously records a feedback signal (for example, a signal correlated or causally linked to an seizure impairment in a subject), and a neurostimulator adjusts parameters of electrode control signals according to the feedback signal. Some implementations herein utilize such a closed-loop stimulation mechanism. In specific examples, specific frequency bands, recorded from an epileptogenic zone, trigger application of electrical stimulus via one or more electrodes to pulvinar neurons having axons projecting to the epileptogenic zone. The sensor electrode can be located in the cortex areas related to the epileptogenic zone (direct closed-loop system) or distant from the epileptogenic zone (remote closed-loop system).
8123-111462-02 [0028] Deep brain stimulation: Direct or indirect application of a stimulus to an area within the brain. In specific implementations herein, selective deep brain stimulation of neurons in somatotopically and/or stereotactically defined pulvinar nuclei is accomplished via electrical stimulation. In alternative implementations, selective deep brain stimulation of neurons in somatotopically and/or stereotactically defined pulvinar nuclei may be accomplished by optical stimulation via implanted optical fibers, magnetic stimulation, or pharmacological stimulation. [0029] Electrical stimulus: The passing of various types of current or voltage selectively through one or more electrodes to a target location in a subject (for example, specific areas of the pulvinar). [0030] Electrode: An electric conductor through which an electric current can pass. An electrode can also be a collector and/or emitter of an electric current. In some implementations, an electrode is a solid and comprises a conducting metal as the conductive layer. Non-limiting examples of conducting metals include noble metals and alloys, such as stainless steel and tungsten. An array of electrodes refers to a device with at least two electrodes formed in any pattern. A multi-channel electrode includes multiple conductive surfaces that can independently activated to stimulate or record electrical current. [0031] Epilepsy: A brain disorder characterized by chronically recurrent seizures resulting from excessive electrical discharges from groups of neurons. Focal epilepsy is characterized by recurrent seizures arising from a specific region of the brain (e.g., the epileptogenic zone). Multifocal (or generalized) epilepsy is characterized by recurrent seizures arising from non-specific and widely diffuse regions in the brain. A significant percentage of individuals with epilepsy have medically refractory epilepsy, which cannot completely be controlled by medical therapy, that is, seizures continue to occur despite treatment with a maximally tolerated dose of anti-epilepsy drugs. [0032] Epileptogenic zone: The minimal area of brain tissue responsible for generating and early organization of recurrent seizure activity in a patient with focal epilepsy. Various non-invasive and invasive methods are available for identification of an epileptogenic zone in a patient. Non-limiting examples of non-invasive techniques include monitoring of neural activity using various forms of scalp-electroencephalography (scalp-EEG), video-EEG, and brain imaging (e.g., MRI, PET, Ictal SPECT), as well as neuropsychological tests and speech-language studies. Non-limiting examples of invasive techniques include monitoring of neural activity using neural implants such as subdural grid and strip electrodes,
8123-111462-02 stereotactically placed depth electrodes (e.g., stereo-EEG or SEEG), which is typically performed in a dedicated Epilepsy Monitoring Unit (EMU). [0033] Implanting: Completely or partially placing a neurodevice (such as a neurostimulator connected to an electrode array) within a subject, for example, using surgical techniques. A neurodevice is partially implanted when some of the device or neurostimulator reaches, or extends to the outside of, a subject. A neurodevice can be implanted for varying durations, such as for a short-term duration (e.g., one or two days or less) or for long-term or chronic duration (e.g., one month or more). [0034] Interictal spikes: interictal spikes (IIS) are large intermittent morphologically defined electrophysiological events observed between seizures in subjects with epilepsy. The spikes are generated by the synchronous discharges of a group of neurons in a region referred to as the epileptic focus. Interictal spikes are highly correlated with spontaneous seizures, and their presence is a factor that can be used to support the diagnosis of epilepsy. [0035] Neural signal: An electrical signal originating in the nervous system of a subject. “Stimulating a neural signal” refers to application of an electrical current to the neural tissue of a subject in such a way as to cause neurons in the subject to produce an electrical signal (e.g., an action potential). An extracellular electrical signal can, however, originate in a cell, such as one or more neural cells. An extracellular electrical signal is contrasted with an intracellular electrical signal, which originates, and remains, in a cell. An extracellular electrical signal can comprise a collection of extracellular electrical signals generated by one or more cells. [0036] Neurostimulator: A current or voltage-controlled electrical stimulation device. A neurostimulator controls the delivery of an electrical pulse, or pattern of electrical pulses, having defined parameters, for example and without limitation, pulse frequency, duration, amplitude, phase symmetry, duty cycle, pulse current, pulse width, and on-time and off-time. The controlled electrical pulse is delivered through one or more electrodes (for example, leadless electrode(s), or electrode(s) located at the end of a lead, a thin insulated wire) configured to apply the electrical stimulus to the brain of a subject. A neurostimulator may comprise at least one multiple contact lead. Neurostimulators may be utilized to apply a series of electrical pulse stimuli (e.g., charge balanced pulses) through at least one electrode; for example and without limitation, low-frequency pulse train patterns, frequency-sequenced pulse burst train patterns (e.g., wherein different sequences of modulated electrical stimuli are generated at different burst frequencies), and phasic train patterns (e.g., wherein the stimulus control parameters change over the course of feedback, from a distal source).
8123-111462-02 [0037] Perceptual threshold: The minimum pulvinar stimulation intensity necessary for a conscious organism to be aware of a particular sensation. [0038] Pulvinar of the Thalamus (Pulvinar): A collection of nuclei located in the posterior and dorsolateral portion of the thalamus, bilaterally. The pulvinars lie posterior, medial, and dorsal to the lateral geniculate nucleus and surround the brachium of the superior colliculus. Each pulvinar contains several nuclei, including medial, lateral, and inferior nuclei, that are most frequently associated with processing of visual information such as saccade movements and visual attention. The lateral and inferior pulvinar nuclei have widespread connections with early visual cortical areas. The dorsal part of the lateral pulvinar nucleus predominantly has connections with posterior parietal cortex and the dorsal stream cortical areas. The medial pulvinar nucleus has widespread connections with cingulate, posterior parietal, premotor and prefrontal cortical areas. [0039] The pulvinar is the most caudal nucleus of the thalamus, extending from the Atrium surface to the rostral plane defined by the habenular nuclei. In a rostral and caudal orientation, the pulvinar occupies the areas located at the floor of the lateral ventricles, more posteriorly, to the thalamus midbrain transition, at the superior colliculus. [0040] The stereotactic coordinated related to the pulvinar and superior colliculus are: in relation to the AC/PC reformatted planes, and having the PC (posterior commissure) as the reference point, coordinates are X: 2-10 mm lateral to the midline plane; Y: 0 to -6 mm posterior to PC; Z: 0 to -6 mm below the AC/PC defined horizontal plane. [0041] Posterior Quadrant Epilepsy (PCE): A focal epilepsy with an epileptogenic zone located in the occipital lobe, parietal lobe, or posterior temporal lobe of the cortex, including intersections thereof. [0042] Seizure: A period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Generalized seizures affect both hemispheres of the brain. A focal seizure affects only one hemisphere. Symptoms of the seizure depend on the location of the abnormally excessive or synchronous neuronal activity, for example, seizure activity in the occipital cortex may induce visual impairment in the patient. [0043] Seizure-induced impairment: Acute changes in biological function due to focal seizures resulting from excessive electrical discharges from groups of neurons. The biological function affected by the focal seizure depends on the neuronal location of the excessive electrical discharge. For example, seizures due to posterior quadrant epilepsy often manifest visual and speech/language impairments. Non-limiting examples of visual impairments due to posterior quadrant epilepsy include seeing bright lights, flashes, or object
8123-111462-02 distortion (e.g., object size, color, shape, etc.), reduced or dysregulated saccade movement of the eye, and reduced capacity for visual attention. Common secondary symptoms include vertigo and impaired balance. Other symptoms and signed related to focal and generalized epilepsy are speech disturbance, motor manifestations as generalized tonic-clonic seizures, sensory manifestation, autonomic manifestations, memory disturbances and loss of consciousness. [0044] Subject: Living multi-cellular vertebrate organisms, a category that includes human and non-human mammals, including non-human primates, rats, mice, guinea pigs, cats, dogs, cows, horses, and the like. Thus, the term “subject” includes both human and veterinary subjects. [0045] Superior colliculus: A paired structure of the dorsal midbrain that forms part of the mesencephalic tectum, and functions in sensory processing, particularly in the integration of visual and auditory information, as well as in the generation of motor responses. The superior colliculi are situated inferior/caudal to the pineal gland and the splenium of corpus callosum, and are overlapped by the pulvinar. The region of the superior colliculus adjacent to the pulvinar in each hemisphere is termed the pulvinar-superior colliculus transition. [0046] Therapeutically effective amount: An amount of a treatment sufficient to provide a beneficial, or therapeutic, effect to a subject or a given percentage of subjects. Therapeutically effective amounts of a treatment can be determined in many different ways, such as assaying for a reduction in a disease or condition (such as visual or speech impairment to due focal seizure). Therapeutic treatments can be administered in a single application, or in several applications (e.g., chronically over an appropriate period of time). However, the effective amount can be dependent on the source applied, the subject being treated, the severity and type of the condition being treated, and the manner of administration. [0047] Treating or treatment: With respect to disease or condition (e.g., visual or speech impairment due to focal posterior quadrant epilepsy), either term includes (1) preventing the disease or condition, e.g., causing the clinical symptoms of the disease or condition not to develop in a subject that may be exposed to or predisposed to the disease or condition but does not yet experience or display symptoms of the disease or condition, (2) inhibiting the disease or condition, e.g., arresting the development of the disease or condition or its clinical symptoms, or (3) relieving the disease or condition, e.g., causing regression of the disease or condition or its clinical symptoms. [0048] Thalamus: A paired structure of gray matter located in the forebrain with nerve fibers projecting to multiple brain structure, including the hippocampus and cerebral cortex.
8123-111462-02 The thalamus is divided into several sections, including the median, medial, anterior, ventral, and posterior thalamus, which contain different nuclei projecting to defined cortical regions. III. Deep Brain Stimulation of Pulvinar to Treat Intractable Seizures [0049] Provided herein are methods for treating a subject (for example, a human subject) having epilepsy, such as medically refractory focal epilepsy. In several implementations, the subject has medically refractory focal epilepsy with an epileptic zone located in the posterior quadrant cortex. Methods according to particular implementations disclosed herein may be utilized to treat (i.e., prevent, ameliorate, suppress, and/or alleviate) a subject’s seizure- induced impairment. [0050] In some implementations, the method comprises applying a therapeutically effective amount of an electrical stimulus to the pulvinar or the superior colliculus with one or more electrodes of a deep brain stimulator implanted in the pulvinar or superior colliculus of the subject, respectively, and controlled by a neurostimulator. The stimulated neurons include projections to a target location of the cortex of the subject that comprises an epileptogenic zone for seizure-induced impairment (such as visual or speech impairment) due to the epilepsy in the subject. The electrical stimulus is applied in an amount sufficient to reduce the seizure-induced impairment in the subject. [0051] In some implementations, the method comprises applying a therapeutically effective amount of an electrical stimulus to the pulvinar with one or more electrodes of a deep brain stimulator implanted in the pulvinar of the subject and controlled by a neurostimulator. The pulvinar neurons include projections to a target location in the posterior quadrant of the cortex of the subject that comprises an epileptogenic zone for seizure-induced impairment (such as visual or speech impairment) due to the focal epilepsy in the subject. The electrical stimulus is applied in an amount sufficient to reduce the seizure-induced impairment in the subject. [0052] In some implementations, the method comprises applying a therapeutically effective amount of an electrical stimulus to the superior colliculus, such as the pulvinar- superior colliculus transition, with one or more electrodes of a deep brain stimulator implanted in the superior colliculus of the subject and controlled by a neurostimulator. The superior colliculus neurons include projections (via the pulvinar) to a target location in the posterior quadrant of the cortex of the subject that comprises an epileptogenic zone for seizure-induced impairment (such as visual or speech impairment) due to the focal epilepsy
8123-111462-02 in the subject. The electrical stimulus is applied in an amount sufficient to reduce the seizure-induced impairment in the subject. [0053] In some implementations, a subject with focal posterior quadrant epilepsy is selected for treatment, and the method comprises implanting a stimulation device (such as a deep brain stimulator) in the pulvinar of the subject. [0054] In some implementations, the method comprises applying a therapeutically effective amount of a stimulus (e.g., an electrical stimulus) to neurons in the pulvinar, wherein the neurons comprise axons projecting to posterior quadrant of the cortex. The electrical stimulus can be applied with one or more electrodes controlled by a neurostimulator. The electrical stimulus reduces the seizure-induced visual impairment in the subject, for example, by reducing the frequency or severity of the seizures. In some implementations, applying the therapeutically effective amount of the stimulus reduces the frequency or severity of the seizures in the subject by at least 50%, such as by at least 75% or elimination of the seizures or the visual impairment induced by the seizures. [0055] In some implementations, a method for treating the subject having epilepsy, such as medically refractory focal epilepsy causing seizures with speech impairment comprises applying a therapeutically effective amount of a stimulus (e.g., an electrical stimulus) to neurons in the pulvinar, wherein the neurons comprise axons projecting to posterior quadrant of the cortex. The electrical stimulus can be applied with one or more electrodes controlled by a neurostimulator. The electrical stimulus reduces the seizure-induced speech impairment in the subject, for example, by reducing the frequency or severity of the seizures. In some implementations, applying the therapeutically effective amount of the stimulus reduces the frequency or severity of the seizures in the subject by at least 50%, such as by at least 75% or elimination of the seizures or the speech impairment induced by the seizures. [0056] Some implementations of methods disclosed herein include the specific stimulation of one or more pulvinar nuclei, for example, one or more of the medial nucleus, the lateral nucleus, or the inferior nucleus of the pulvinar. In particular implementations, stimulation of specific areas of the pulvinar targets fibers connecting the pulvinar to the posterior quadrant of the cortex to an extent sufficient to suppress epileptiform activity in the epileptogenic zone. In some implementations, the electrical stimulus is not applied to non-pulvinar areas of the of the thalamus. In some such implementations, the deep brain stimulator is implanted to target neurons within a region of the pulvinar defined by AC/PC stereotactic coordinates, such as the medial nucleus, the lateral nucleus, or the inferior nucleus of the pulvinar.
8123-111462-02 [0057] In some implementations, the electrical stimulus includes electrical pulses defined by parameters including, for example and without limitation, amplitude, pulse width, and pulse frequency. Such electrical pulses may include charge-balanced pulses. In these and further implementations, the electrical stimulus may be a continuous electrical stimulus, and/or a closed-loop electrical stimulus. [0058] In particular examples, the electrical stimulus includes electrical pulses with an amplitude of less than about 10 mA; for example, less than 10 mA, less than 9 mA, less than 8 mA, less than 7 mA, less than 6 mA, less than 5 mA, less than 4 mA, less than 3 mA, less than 2 mA, or less than 1 mA. In particular examples, the electrical stimulus includes electrical pulses with pulse widths between about 80 µs and about 2 ms; for example, between 80 µs and 2 ms, between 100 µs and 2 ms, between 200 µs and 2 ms, between 300 µs and 2 ms, between 400 µs and 2 ms, between 500 µs and 2 ms, between 600 µs and 2 ms, between 700 µs and 2 ms, between 800 µs and 2 ms, between 800 µs and 2 ms, between 900 µs and 2 ms, between 1 ms and 2 ms, between 1.5 ms and 2 ms, between 80 µs and 1.5 ms, between 100 µs and 1.5 ms, between 200 µs and 1.5 ms, between 300 µs and 1.5 ms, between 400 µs and 1.5 ms, between 500 µs and 1.5 ms, between 600 µs and 1.5 ms, between 700 µs and 1.5 ms, between 800 µs and 1.5 ms, between 800 µs and 1.5 ms, between 900 µs and 1.5 ms, between 1 ms and 1.5 ms, between 1.5 ms and 2 ms, between 80 µs and 1 ms, between 100 µs and 1 ms, between 200 µs and 1 ms, between 300 µs and 1 ms, between 400 µs and 1 ms, between 500 µs and 1 ms, between 600 µs and 1 ms, between 700 µs and 1 ms, between 800 µs and 1 ms, between 800 µs and 1 ms, and between 900 µs and 1 ms. In particular examples, the electrical stimulus includes a pulse frequency between about 100 Hz and about 1000 Hz; for example, between 50Hz and 1000Hz, between 100 Hz and 1000 Hz, between 100 Hz and 900 Hz, between 100 Hz and 800 Hz, between 100 Hz and 700 Hz, between 100 Hz and 600 Hz, between 100 Hz and 500 Hz, between 100 Hz and 400 Hz, between 100 Hz and 300 Hz, and between 100 Hz and 200 Hz. In some implementations, the pulse frequency is between 100Hz and 250Hz. [0059] Accordingly, the electrical stimulus in particular implementations herein includes electrical pulses having an amplitude of less than about 10 mA, a pulse width of between about 100 µs and about 2 ms, and a pulse frequency between about 100 Hz and about 1000 Hz, such as between about 100Hz and about 250Hz or between about 150 Hz and about 200 Hz. [0060] In particular implementations, the stimulation is applied at or below the subject’s perceptual threshold.
8123-111462-02 [0061] In some implementations, disclosed methods are effected by the use of an implanted neurostimulator that controls the stimulation (e.g., electrical stimulation via one or more implanted electrode(s)) according to predetermined parameters or parameters determined by feedback in a closed-loop system. In particular implementations, methods disclosed herein can be used in combination with rehabilitation therapy to improve long-term recovery outcomes. [0062] Deep brain stimulation is an advanced neurosurgical procedure involving the implantation of one or more electrode(s) that deliver an electrical stimulus under the control of an externalized or implanted neurostimulator unit. Implantation of the electrode(s), and/or a neurostimulator in examples where the neurostimulator is not externalized, is typically performed by a clinical team including neurologists, neurosurgeons, neurophysiologists, and other specialists trained in the assessment, treatment, and care of neurological conditions. Typically, following selection of an appropriate subject and determination of the area of the subject’s brain to be stimulated, precise placement of at least one electrode in the area of the patient's thalamus or subthalamus is carried out in an operating room setting, typically utilizing brain imaging technology and stereotactic targeting made possible by the stereotypical organization of different areas of the thalamus or subthalamus. After administration of local anesthesia, the subject undergoing electrode implantation experiences little discomfort, and is generally kept awake during the implantation procedure to allow communication with the surgical team. [0063] Some implementations herein employ an implant that includes one or more electrodes and/or neurostimulator implanted (e.g., fully or partially implanted) in the brain of a subject. Further implementations herein employ an implant that includes one or more magnets or optical fibers, and/or a neurostimulator implanted in the brain of a subject. [0064] Numerous types and styles of neural implants (for example, implants including one or more electrodes for providing an electrical stimulus) are available and known to those in the art. Any neural implant for specific stimulation of a thalamic or subthalamic area in a subject may be utilized in specific implementations. In some implementations, more than one electrode is implanted, such as an array of electrodes. In additional implementations, a device is provided that can include one or more electrodes. Non-limiting examples include deep brain stimulators, EcoG grids, electrode arrays, microarrays (e.g., Utah and Michigan microarrays), and microwire electrodes and arrays. [0065] In some implementations, an implanted neurostimulator can be used for stimulating bio-electric (e.g., neural) signals to thalamic and subthalamic area in the subject. For
8123-111462-02 example, an implanted neurostimulator may be implanted so as to specifically stimulate one or more area of a subject’s ventral thalamus for a period of at least 1 month; for example, at least 2, 6, 12, 18, 24, 30, 36, or more months. [0066] In some implementations, circuitry is implanted connecting a neurostimulator to the one or more electrodes. In particular implementations, the circuits are fully implanted (typically in a subcutaneous pocket within a subject’s body), or are partially implanted in the subject. The operable linkage of the neurostimulator to the electrode(s) can be by way of one or more leads, although any operable linkage capable of transmitting a stimulation signal from the circuitry to the electrodes may be used in specific implementations. [0067] In some implementations, electrodes used in accordance with the invention are positioned in specific areas of the brain (such as the pulvinar), so as to be capable of selective application of an electrical stimulus to the specific area, by any of the methods conventionally used for positioning of electrodes for deep brain stimulation. As is known in the art, the particular procedures used will vary according to the available equipment, training of personnel, and the circumstances of each case. In some examples, the procedures for placement and testing of electrodes are divided into several steps including mounting of a stereotactic ring on the patient’s skull, and imaging by high resolution stereotactic commuted tomographic (CT) scanning of the head. The stereotactic CT scan is preferably preceded by high resolution, volumetric, and three tesla magnetic resonance imaging (MRI) in advance of placement of the stereotactic head ring. Planning of the surgical target sites within the brain and trajectories for approach to the selected targets can be achieved using the MRI images and computer software designed for stereotactic targeting, for example, Stereoplan™ Plus 2.3 (Stryker-Leibinger, Friedburg, Germany), and SNS™ 3.14 (Surgical Navigation Specialists, Mississauga, Canada). [0068] Post-operative control of selective electrical stimulation of the pulvinar and/or superior colliculus by the implanted electrode is provided in some implementations by a neurostimulator that may be externalized or implanted; for example, subcutaneously (e.g., in the chest or belly of the subject). Following recovery from the implantation, surgery, and connection of electrode leads to the neurostimulator, the subject may be monitored and tested to establish parameters for the electrical stimulation based on the subject’s condition. In some implementations, electrical stimulation by the implanted electrode(s) is delivered to at least one specific area of the subject’s pulvinar while the subject is monitored for seizure activity. In some implementations, the parameters of the electrical stimulus controlled by the neurostimulator are adjusted according to changes in the seizure activity due to the applied
8123-111462-02 stimulus, for example, so as to reduce the frequency or severity of seizures with minimal side effects due to the applied electrical stimulus. In specific implementations, the operation of the device and/or the neurostimulator can be at least partially under the control of the subject once the subject is released from a clinical setting. For example, the subject can activate the neurostimulator in response to sensation of an aura of the focal epilepsy. In these and further implementations, the subject is taught how to use the device and/or the neurostimulator. EXAMPLES [0069] The following examples are provided to illustrate particular features of certain implementations, but the scope of the claims should not be limited to those features exemplified. Example 1 Deep Brain Pulvinar Stimulation for Seizure Suppression in a human [0070] This example illustrates neurostimulation of the pulvinar to suppress epileptiform activity in the epileptogenic zone of the posterior quadrant cortex in a human subject. [0071] Current understanding of specific changes in pulvinar-cortical communication during focal seizures is inadequate. Evidence provided in this example characterizes the dynamic relation between pulvinar nuclei and seizure activity in the posterior quadrant cortex, and demonstrates the suppression of epileptiform activity in the posterior quadrant with high-frequency stimulation of the pulvinar. Methods [0072] Epilepsy patients were admitted to the Epilepsy Monitoring Unit (EMU) of the University of Pittsburgh Medical Center for a bilateral stereoelectroencephalography (SEEG) implantation to map the epileptogenic zone. During their stay in the EMU, brain activity was continuously recorded from 15 SEEG electrodes using the NATUS™ Medical system. SEEG electrodes include 12 to 18 recording contacts. The implantation sites were planned to cover all areas suspected of epileptogenesis, and realized through a robotic approach to ensure accuracy. The epileptogenic zone for several patients was defined as a focal area in the parietal or occipital lobe. Additionally, one of the SEEG electrode trajectories passed through the pulvinar nucleus, in particular targeting the medial pulvinar and the lateral pulvinar. This allowed simultaneous stimulation of the pulvinar and recording from multiple
8123-111462-02 areas of the brain, including the epileptogenic zone in the parietal or occipital cortex (depending on patient). [0073] Ictal analysis: While the patient was monitored in the EMU, we recorded spontaneous ictal events (i.e., seizures). For each of these, we analyzed correlation between bipolar signals locally recorded from different regions of interest, including the pulvinar nucleus and the epileptogenic zone. In order to quantify the interaction between the selected regions and to compare them with background activity, we chose three periods of interest: (i) background activity: including 10s to 2 min before the onset of an ictal discharge and was used as a reference period; (ii) seizure onset: including the first 10s after the beginning of a low-voltage fast activity; and (iii) seizure termination: including the last 10s of the seizure discharge. For each of these periods, we calculated the h2 coefficient, a non-linear correlation coefficient that evaluates the functional connectivity across two regions. [0074] Electrical Stimulation: Stimulation was applied to the pulvinar using the SEEG electrodes at frequencies varying from 1 to 200Hz. Pulse width was set to 100 µs and amplitude was set to 1-5 mA. The behavior of epileptogenic discharges (i.e., interictal spikes) in the epileptogenic zone was monitored. Specifically we evaluated the rate of interictal spikes and their amplitude in three time windows: pre stimulation (30 seconds before the stimulations was applied), stimulation (while stimulation was applied) and post stimulation (considering the 30 seconds after stimulation was interrupted). We used bootstrap to assess statistical significance among these intervals. Results [0075] Electrophysiological experiments were performed on five human patients affected by posterior quadrant epilepsy with an epileptogenic zone in the parietal or occipital cortex. Patients were selected from those admitted to the Epilepsy Monitoring Unit (EMU) of the University of Pittsburgh Medical Center for a bilateral SEEG implantation to map the epileptogenic zone. One of the SEEG electrodes passed through the pulvinar nucleus. [0076] First, to confirm connections between the pulvinar and epileptogenic zone, low frequency electrical stimulation of the pulvinar was performed, with concurrent recording of cortical evoked potentials. a preferential connectivity of the pulvinar nucleus for posterior quadrant regions was observed (FIG.1). [0077] While the patients were monitored in the EMU, spontaneous ictal events (i.e., seizures) were recorded. For each of these, the correlation between bipolar signals locally recorded from different regions of interest, including the pulvinar nucleus and the
8123-111462-02 epileptogenic zone, was assessed. In order to quantify the interaction between the selected regions and to compare them with background activity, three time periods of interest were assessed: (i) background activity: including 10 s to 2 min before the onset of an ictal discharge was used as a reference period; (ii) seizure onset: including the first 10 s after the beginning of a low-voltage fast activity; and (iii) seizure termination: including the last 10 s of the seizure discharge. For each of these periods, we calculated the h2 coefficient, a non- linear correlation coefficient that evaluates the functional connectivity across two regions. [0078] The connectivity analysis revealed an involvement of the pulvinar observed during the course of the analyzed seizures in the epileptogenic zone. As depicted in FIG.2, the correlation between the pulvinar and the epileptogenic zone (moto cingulate) was maximal around seizure termination. These results suggest that a pulvinar-cortical coupling could appear early after the onset of focal posterior quadrant seizures and then sustainably increase until raising its maximal level at seizure termination. [0079] We then applied electrical stimulation to the pulvinar at 100 Hz (100µs, 1-5mA) and monitored the behavior of epileptogenic discharges (i.e., interictal spikes) in the epileptogenic zone. Specifically, we evaluated the rate of interictal spikes and their amplitude in three time windows: pre-stimulation (30 seconds before the stimulations was applied), during stimulation (while stimulation was applied) and post-stimulation (considering the 30 seconds after stimulation was interrupted). A bootstrap analysis to assess statistical significance among these intervals. [0080] As shown in FIG.3, electrical stimulation of the pulvinar nucleus of the thalamus affected the epileptogenic zone. High frequency stimulation (100 Hz) significantly decreased both the rate and amplitude of pathological interictal spikes. These parameters are in line with the stimulation parameters clinically exploited in the field of Deep Brain Stimulation for epilepsy. EXAMPLE 2 Pulvinar Stimulation to Personalize Electrical Stimulation for Focal Epilepsy [0081] This example shows that, for focal epilepsy, thalamic electrical stimulation that matches the hodology of the thalamocortical pathway enhances therapeutic outcome, particularly for stimulation of the pulvinar. In other words, targeting electrical stimulation to the thalamic subnucleus (particularly the pulvinar) with preferential anatomical and functional connectivity to the seizure onset zone (SOZ) (an approach referred to as hodological matching) improves the efficacy of thalamic stimulation for the treatment of
8123-111462-02 refractory focal epilepsy. This hodology-based treatment approach achieved a median reduction in seizure frequency of 86.5%, which dramatically outperforms unmatched thalamic targeting reported by literature (39%). Results Study rationale and design [0082] Specific thalamic subnuclei were investigated for increased efficacy in the treatment of focal refractory epilepsy based on their hodological matching with the cortical SOZ. A large array of electrophysiological and imaging assessments was employed in a unique cohort of 32 focal MRE patients (Figure 4a and Table 1 for demographic and clinical information for each patient). Specifically, intracranial electrophysiological data from 26 patients (S01-S26) undergoing (SEEG) exploration for epilepsy monitoring was analyzed (Figure 4b). Prior to SEEG implantation, preoperative structural magnetic resonance imaging (MRI) and postoperative computed tomography (CT) for precise SEEG contacts localization performed by a certified neurosurgeon (JGM) in all patients were acquired. All the participants had at least one SEEG electrode located in one of the nuclei of interest, namely the pulvinar (PUL), anterior nucleus (ANT), and ventral intermediate nucleus/ventral oral posterior nuclei (VIM/VOP), and a diagnosis of focal epilepsy. Overall, 37 thalamic nuclei among those of interest were sampled in this cohort (Figure 4b, Table 2). Each patient’s SOZ was categorized as frontal (meaning originating from frontal lobe regions such as the orbitofrontal cortex), temporal (including mesial and lateral temporal lobe structures), rolandic (including pre- and post-central peri-rolandic regions) or parietal/occipital cortex (namely originating from posterior-quadrant areas) (Figure 4c, Table 3). In a subgroup of patients (n=8), high-resolution diffusion MRI data was acquired and analyzed to corroborate the anatomical organization of thalamocortical fibers (Figure 4f). Such connectivity pattern was also confirmed through electrophysiology with thalamocortical evoked potentials (n=6). To study the interaction of the thalamus and the epileptic cortex, a total of 216 spontaneous seizures with concurrent sampling of the thalamic nuclei and cortical SOZ were then analyzed. Hence, each recorded seizure was categorized according to the SOZ anatomical location and the sampled thalamic nucleus during the event (Figure 4c). Electrophysiological testing in a subset of patients was then performed. Specifically, high- frequency thalamic stimulation (n=14) was used to test immediate effects of hodologically- matched thalamic stimulation on interictal epileptiform activity (Figure 4f). Finally, long- term efficacy of the hodology based neuromodulation approach in 7 patients (S16, S27-32)
8123-111462-02 with a chronic stimulation implant (Figure 4d) was assessed with up to 3 years of follow-up (Figure 4d-e). [0083] Table 1. Patient demographic and epilepsy type (SPS = simple partial seizure, CPS = complex partial seizure, GTC = general tonic seizure). Gray cells indicate the patients who were chronically implanted with a hodologically-matched neurostimulation system. Subject Gender Age at Age at seizure Duration Type of SOZ N surgery onset of epilepsy seizure/semiology tal
8123-111462-02 19 M 25-29 20 7 SPS + CPS Temporal tal tal tal
[0084] Table 2. Thalamic coverage and performed experiments for SEEG population (S1-S26). Subject Thalamic Coverage Spontaneous Seizures DTI EP Acute N ti l ti n
8123-111462-02 7 x 10 X
8123-111462-02 [0085] Table 3. Anatomical location of SOZ and non-SOZ regions for SEEG population. Subject SOZ SOZ anatomical area non-SOZ area 1 non-SOZ area 2 non-SOZ area 3 N categorizat i n ) s d / al us us t al al la al
8123-111462-02 20 Superior temporal Temporal Mesial temporal lobe sulcus Orbitofrontal Orbitofrontal gyrus te s l le
[0086] The presence of a well-defined anatomical map of the thalamocortical projections of PUL, ANT and VIM/VOP in the epileptic brain was confirmed with two complementary methodologies: neuroimaging and electrophysiology. [0087] First, high-definition fiber tracking (HDFT) of high-resolution diffusion MRI data was performed to confirm previously reported anatomical organization of cortical connectivity patterns of the PUL, ANT and VIM/VOP. All the likely axonal pathways between these nuclei and the cortical regions presenting seizures in our cohort (namely frontal, rolandic, parietal, occipital and temporal) were reconstructed (Figure 5a). The relative strength of these connections was quantified by calculating the volume of thalamocortical projections from each nucleus to each cortical region normalized by the total volume of fibers (Figure 5b). This analysis revealed a clear thalamocortical anatomical organization. Indeed, the PUL showed preferential connectivity towards the parietal and occipital regions, and the temporal lobe (mean volume value, frontal 0.11, rolandic: 0.04, parietal: 0.38, occipital: 0.27, temporal: 0.18); the ANT, instead, presented axonal projections going preferentially towards the frontal and temporal lobes (frontal: 0.39, rolandic: 0.05, parietal: 0.06, occipital: 0.16, temporal: 0.31); finally the VIM/VOP nuclei projected more remarkably to the rolandic cortex (frontal: 0.29, rolandic: 0.56, parietal: 0.03, occipital: 0.06, temporal: 0.03). This constricted structure of thalamocortical fibers from PUL, ANT and VIM/VOP contrasts with the broad anatomical connectivity of the CM (frontal: 0.27, rolandic: 0.17, parietal: 0.19, occipital: 0.19, temporal: 0.15), hence
8123-111462-02 corroborating its indication as a more suitable target in generalized epilepsy (Figure 10a- 10b). [0088] This anatomical organization was then confirmed by analyzing thalamocortical evoked potentials (EPs) in the different cortical areas. For this, low frequency (1 Hz) electrical stimulation was applied to the different thalamic nuclei at 1-3 mA while recording cortical neural response evoked by each pulse in the different cortical lobes (Figure 5d, 5g, 5j). Stimulation triggered averages of EPs was analyzed. Following thalamic stimulation, robust cortical EPs in anatomically connected (i.e., matching), but not in unmatching, cortical regions were observed (Figure 5e, 5h, 5k). Indeed, analysis of EPs peak to peak amplitudes showed significantly larger responses in those areas that matched the previously identified projections, further confirming a precise anatomical organization of distinct thalamic nuclei (Figure 5c, 5f, 5i, 5l). [0089] In summary, a specific anatomical organization of the thalamocortical projections of PUL, ANT and VIM/VOP in the studied population were confirmed with multiple techniques. Hodologically-matching (parietal, occipital and temporal for PUL, frontal and temporal for ANT, and rolandic for VIM/VOP) and unmatching (frontal and rolandic for PUL, rolandic, parietal and occipital for ANT, frontal, temporal, parietal and occipital for VIM/VOP) regions were defined . Increased thalamocortical coupling during seizures in hodologically-matching SOZs [0090] Given this specific structural organization of the thalamocortical fibers, a preferential functional involvement in the course of spontaneous seizures of the thalamic subnucleus that anatomically matches the SOZ was assessed (Figure 6d). A total of 216 spontaneous (i.e., not induced by cortical electrical stimulation) ictal events were analyzed. The anatomical location of the SOZ as well as the relevant time markers (pre-ictal, beginning and end) of each seizure were determined. For each seizure the non-linear h2 correlation coefficient29,46–48 was computed to identify time-resolved synchrony between each thalamic nucleus and each cortical SOZ. Specifically, mean h2 coefficient during the ictal event (from seizure onset to termination) and the mean h2 coefficient during a 10 second baseline epoch spaced 2 minutes apart from the seizure’s onset were computed (see Guye, M. et al. The role of corticothalamic coupling in human temporal lobe epilepsy. Brain J. Neurol.129, 1917– 1928, 2006). The mean h2 coefficient between the two phases was compared separately for anatomically connected and non-connected thalamic nuclei to quantify the degree of specificity of thalamic involvement during spontaneous seizures.
8123-111462-02 [0091] It was found that while anatomically matched nuclei showed a significant increase of synchrony between the thalamus and the SOZ, indicating functionally specific thalamic involvement during ictal events (Figure 6a), minimal or no correlation was found in unmatched nuclei (Figure 6b-6c). This was consistent for all thalamic nuclei of interest and subjects (Figure 6e, mean h2 was 0.13 vs 0.20 in matched with p<0.001, and 0.12 vs 0.11 with p>0.05 in unmatched, for baseline and seizure respectively). Importantly, it was observed that thalamic nuclei had minimal or no correlation with non-SOZ regions (FIG. 11A-11B), demonstrating the specificity of the correlation with the anatomically-matched SOZ. Additionally, for a patient diagnosed with generalized epilepsy, it was found that PUL, ANT, and VIM/VOP nuclei had a lower correlation with the epileptogenic zone (0.16, 0.25, 0.21 mean h2 across 24 seizures and 13 channels for PUL, ANT, and VIM/VOP, respectively) as compared to the CM (0.3, Figure 10c-10d). This confirms the more diffused profile of the CM connectivity (both anatomically and functionally), entailing its suitability for generalized, rather than focal epilepsy treatment. Overall, these functional outcomes robustly validated the thalamocortical anatomical organization observed with fiber tracking and thalamocortical EPs, further supporting the definition of hodologically-matching and unmatching nuclei. [0092] To further investigate possible mechanisms of thalamocortical interactions during focal seizures, the coupling of the thalamus and SOZ in terms of seizure phases and frequency bands for matched thalamic nuclei was explored. First, it was assessed whether maximal coupling of matched nuclei was specific to distinct seizure phases. To this aim, the mean h2 correlation coefficient in three epochs was computed: seizure initiation (including the 10 seconds preceding the first appearance of a tonic discharge in the SOZ contacts), middle part of the seizure (defined as the time interval separating seizure initiation and termination), and seizure termination (which includes the last 10 seconds of discharge). The highest synchrony between the thalamus and SOZ occurred at seizure termination (Figure 6f). This behavior was present for all three thalamic nuclei when hodologically (i.e., anatomically and functionally) matched to the SOZ (FIG.11C). These findings support and validate the notion that synchronization loops between the thalamus and cortex might contribute to the termination of seizures. [0093] Additionally, it was sought to determine if the observed synchrony presented a specific spectral profile. Hence, the mean h2 coefficient computed in different frequency bands of the intracerebral recordings (delta, theta, alpha, beta, low gamma, high gamma, ripple, fast ripple) was compared. No spectral specificity was revealed: indeed, for all the
8123-111462-02 frequency bands except the fast ripple band, the correlation between hodologically-matched thalamic nuclei and SOZ always increased significantly during the ictal event, while it showed no variation for unmatched thalamic nuclei (FIG.11D). Hence, whether specific frequency bands would better distinguish hodologically-matched and unmatched nuclei potentially suggesting biomarkers for the refinement of the stimulation design was assessed. For this, the increase in ictal correlation respect we compared to baseline between hodologically-matched and unmatched nuclei in different frequency bands. Interestingly, it was found that theta, alpha and beta frequencies had a higher difference between the h2 correlation change during seizures between hodologically-matched and unmatched nuclei (Figure 6g). These results show that the theta-beta frequencies might be more relevant to differentiate thalamic nuclei based on their connectivity to the SOZ. [0094] These findings demonstrate that thalamic nuclei exhibit enhanced neural synchrony with hodologically-matched cortical SOZs, particularly at the period of seizure termination, and primarily driven by theta, alpha, and beta oscillations. Thalamocortical synchrony revers directionality during spontaneous seizure [0095] While the h2 index revealed an increase in correlation between the hodologically- matched thalamic nuclei and the SOZ throughout the seizure course, it was sought to determine the directionality of this coupling. The directionality of the coupling of hodologically-matched thalamocortical synchrony during spontaneous seizures by investigating was assessed. To this purpose, Granger Causality (GC; see Granger, C. W. J. Investigating Causal Relations by Econometric Models and Cross-spectral Methods. Econometrica 37, 424–438, 1969) between the thalamic nuclei of PUL, ANT and VOP/VIM and the hodologically-matching SOZs was used. Since previous results suggest a crucial role in the theta-alpha-beta oscillations, for this analysis only band-passed filtered (4-30 Hz) seizures that showed a clear increase in h2 coefficient in this frequency range and lasted at least 10 seconds were included. This resulted in a total of 98 seizures. For each seizure, two 10 s epochs of interest at seizure initiation and seizure termination were extracted and the GC matrix for the SOZ contacts and the hodologically-matching thalamic nucleus contacts was computed (Figure 7a). GC of unmatched nuclei was not explored because of the lack of correlation with SOZ. To test whether the role of different thalamic nuclei was changing over the course of the seizure, the GC coefficient from the thalamus towards the SOZ (th^SOZ) and from the SOZ towards the thalamus (SOZ^th) were compared
8123-111462-02 [0096] At seizure initiation, in the majority of the seizures (70%), the GC coefficient of SOZ^th was higher than the GC coefficients th^SOZ (Figure 7b) suggesting a leading role of the cortex. In contrast, more than half of the events (60%) presented a higher th^SOZ coefficient at the termination of ictal events hence indicating a change in the leading anatomical structure. This could be due to 1) SOZ^th decreasing while th^SOZ remaining stable (or decreasing less) throughout the course of the seizure, 2) th^SOZ increasing and SOZ^th remaining stable (or increasing less). To test for this, the relative change of the GC coefficient between termination and initiation was computed and compared between SOZ^th and th^SOZ. Interestingly, an increase in both the thalamocortical (th^SOZ) and corticothalamic (SOZ^th) coupling was observed throughout the duration of the event (Figure 7c). However, the relative change was higher for the th^SOZ consistently across all the subjects, further demonstrating a leading role of the thalamus at seizure termination (73.41 vs 345.6%, for SOZ^th and th^SOZ, respectively) (Figure 7c-7d). [0097] In all studied nuclei, the absolute GC value in the initiation epoch and termination epoch showed a reverse trend, with a primary leading role of the cortex at first (85% for PUL, 59% for ANT, 60% for VIM/VOP), followed by a predominantly leading role of the thalamus at termination (63% for PUL, 71% for ANT, 52% for VIM/VOP) (Figure 7e). Additionally, PUL, ANT and VIM/VOP showed a significantly higher relative change for th^SOZ throughout the seizure (Figure 7f). [0098] In summary, the underlying mechanisms of thalamocortical and corticothalamic coupling involving the ANT, PUL and VIM/VOP with hodologically-matched SOZ during spontaneous seizures were investigated. The findings suggest that cortical regions exert a dominant influence at seizure initiation, while the thalamus may assume a more prominent role as the ictal events progresses. This pattern was observed across all three nuclei tested, suggesting that the development of nuclei-specific stimulation protocols -particularly regarding the timing of stimulation during the ictal event- may not be necessary to address the varying underlying mechanisms of thalamic action. Matched thalamic stimulation immediately suppresses epileptiform discharges [0099] Given the peculiar hodology found both in the structural connectivity of the PUL, ANT and VIM/VOP, as well as in the functional coupling observed during ictal events, targeting electrical stimulation to the thalamic nucleus that hodologically-matches the cortical SOZ was assessed in reducing epileptiform activity compared to unmatched nuclei. Bipolar thalamic stimulation was delivered through the SEEG electrodes in 14 patients. For clinical
8123-111462-02 reasons, the stimulation testing was always performed after the patient had shown spontaneous seizures. The effect of hodologically-matched and unmatched stimulation was assessed on interictal epileptiform discharges (IEDs), namely interictal spikes. An automatic validated algorithm was used to extract IEDs from cortical recordings in the SOZ (Figure 8a), previously subdivided in 5 seconds epochs and denoised (see Methods). The difference between baseline (including the epochs in the 2 minutes preceding the first stimulation applied) and stimulation epochs was quantified (see Methods). For this, two distinct analyses were performed: a) in n=8 patients with continuous evident pathological spiking (Figure 8a), the rate of IEDs per minute in baseline (Stim OFF) and stimulation (Stim ON) epochs were computed; b) in n=6 patients with more than half of the baseline epochs without pathological spikes, the probability of suppressed IEDs in stimulation epochs were computed and compared to the probability of suppressed IEDs in baseline epochs, hence obtaining a percentage change in IED suppression probability (Table 2). In the first analysis, a positive effect of the stimulation (meaning reducing pathological IEDs) should result in a smaller IEDs rate during stimulation epochs than during baseline (stimulation off) epochs; whereas in the latter, a positive number indicated that the stimulation epochs are more likely to present no IEDs than the baseline epochs (without stimulation). [0100] It was found that electrical stimulation of the PUL, ANT and VIM/VOP significantly suppressed cortical IEDs when the SOZ was in a cortical region that hodologically-matched the thalamic nucleus stimulated (Figure 8b-8d, 8g). Overall, the analysis revealed that hodologically-matched but not unmatched thalamic stimulation significantly reduced the IED rate in all tested patients (for matched stimulation, IED variation to baseline ranged from -29.12% to -73% with p<0.01 and p<0.001, while for unmatched stimulation, it ranged from -4.2% to -25%) (Figure 8g). The IED rate values for a representative patient for each nucleus of interest are highlighted: a reduction of the IED rate of 132 vs 78 spikes/minute for the PUL (median rate at stimulation off vs stimulation on in S01, p<0.001) was observed (Figure 8b), 144 vs 60 spikes/minute for the ANT (in S24, p<0.001) (Figure 8c), and 132 vs 48 spikes/minute in the VIM/VOP (in S13, p<0.001) (Figure 8d). Similarly, when evaluating the percentage change in the probability of IED suppression, it was found that hodologically-matched thalamic stimulation epochs were more likely to present no IEDs when compared to unmatched thalamic stimulation epochs. Indeed, in 5 out of 6 patients that received stimulation in the nucleus matching their SOZ, at least a 20% increase (up to over 200%) in the probability of epochs with no IEDs with stimulation on with respect to stimulation off was observed (Figure 8h); whereas the stimulation effect
8123-111462-02 was more inconsistent (-17 to +7%) when the targeted nucleus was not matching the hodology of the thalamocortical fibers towards the SOZ (Figure 8h). This finding further suggests that the more effective thalamic target to suppress IEDs is the one matching the hodology of the SOZ. [0101] Targeted electrical stimulation of the nuclei hodologically-matching the SOZ significantly reduced the rate of IEDs and increased the probability that stimulation epochs present no IEDs (complete suppression). Matched thalamic electrical stimulation in chronic epilepsy treatment [0102] Finally, to verify whether the observed immediate effects on IEDs could be translated in a long-term clinical improvement in epileptic patients, 7 patients (one of which being part of the SEEG cohort) that were chronically implanted for thalamic stimulation in a hodologically-matching thalamic nucleus as part of their clinical care were evaluated. Across all patients, 6 (S16, S27-S31) presented focal MRE originating from the posterior quadrant regions and hence received a neurostimulation system in the PUL, while one (S32) was implanted in the ANT to treat a frontal onset MRE (Table 4). Overall, a median reduction in seizure frequency of 86.5 % (Figure 9a, 9b) was observed at 15.86±7.9 (mean±SD) months of follow-up. As a representative example, for S16 seizures reduced from 5 per week to 1 per month, and the patient also self-reported a significant reduction in seizure severity, noting no missed workdays since the implant of the stimulation device, compared to missing 1-2 days per month prior to surgery. Additionally, the anti-seizure medication (ASM) intake for each patient decreased for 5/7 patients since the matched neurostimulation system was implanted, and did not increase for any of the participants (Figure 9c). Importantly, these results dramatically outperform the unmatched thalamic stimulation results reported in literature for the SANTE trial at 7 years follow-up. Indeed, in this previous study, unmatched stimulation (ANT stimulation for seizure onsets other than frontal or temporal) only achieved 39% reduction in seizure frequency, whereas outcome for matched SOZ were comparable to the ones we observed (78% and 86% for temporal and frontal onset, respectively). [0103] Table 4. Details about chronic participants and chronic implant received. Subject Target Follow-up Stimulation Stimulation SOZ l
8123-111462-02 27 PUL 12 142.9 1.3 Occipital/Parietal l l
, ulation provides significant therapeutic benefits, including notable reductions in the frequency and severity of disabling seizures. This approach not only outperforms current standard treatments but also lays the groundwork for more personalized and precise target selection in neuromodulation for medically refractory focal epilepsy, particularly in patients who are not candidates for curative resective or ablative interventions. Discussion [0105] Here, we proposed a novel approach to select the optimal targets for thalamic electrical stimulation in focal epilepsy, considering the specificity of SOZs in relation to cortical and subcortical anatomy. Specifically, we demonstrated that leveraging the hodology-based interactions between certain subnuclei of the thalamus and the epileptogenic cortex results in stronger neuromodulator efficacy. This approach highlights the importance of thalamocortical hodology in individualizing stimulation targets, potentially advancing therapeutic outcomes, and paving the way for more effective neuromodulation strategies in patients with focal MRE who are not candidates for curative interventions. [0106] The results demonstrate that hodologically-matched thalamic stimulation immediately suppresses interictal epileptiform discharges, particularly for pulvinar stimulation. Additionally, this targeted stimulation markedly enhances the likelihood of achieving complete suppression of IEDs during stimulation epochs, indicating robust utility for targeted thalamic stimulation as a therapeutic strategy in epilepsy neuromodulatory management. Immediate effects in n = 14 subjects, paralleled with the drastic clinical improvement in seizure frequency with chronic matched thalamic stimulation (up to 95%) in seven patients, provide evidence that a hodology-based stimulation improves clinical
8123-111462-02 outcome for patients with focal epilepsy. Importantly, the comparative results show a substantial improvement over existing literature on unmatched thalamic neuromodulation (86.5% versus 39% reduction in seizure frequency), highlighting the potential need to reconsider current clinical practices, where a single target is often applied to all seizure onset zones. Methods Trial and participants information [0107] All experimental protocols were approved by the University of Pittsburgh Institutional Review Boards (IRB) (protocol STUDY20070113 and STUDY21020058). All participants included in this study were diagnosed with drug-refractory epilepsy and underwent stereoelectroencephalography (SEEG) implantation at the University of Pittsburgh Medical Center as a part of their standard clinical care. They were hospitalized in the epilepsy monitoring unit (EMU) from January 2021 to May 2024, for 5.04±6.28 days (mean±SD). All patients received a comprehensive neurological assessment, neuropsychological testing, routine MRI and CT and SEEG implantation. Informed consent was obtained from all patients or legal representatives. In order to study the anatomical and functional properties of the thalamus and the epileptic cortex via SEEG monitoring, patients (S01-S26) were retrospectively included in the study if: 1) at least one SEEG electrode contact was in the PUL, ANT or VIM/VOP, and 2) at least one of the electrophysiological recordings analyzed in the study was performed (minimum 2 spontaneous seizures, thalamocortical evoked potentials, HDFT, thalamic stimulation). Exclusion criteria encompassed refusal in participating in the study and SEEG implantation complication (severe intracranial hemorrhage). Additionally 7 participants (S16, S27-S32) were included that received a chronic thalamic stimulation system as part of their clinical care to evaluate long-term efficacy of matched thalamic stimulation. [0108] A comprehensive overview of the patients’ demographics and epilepsy categorization, summary of the experiments, and a summary of the data collected for each patient are reported in Tables 1&2. Overall, 26 SEEG participants were included (20 males, 6 females) and 7 chronically implanted patients (S16, S27-S32), of age 34.8±11.3 (mean±SD). The age at seizure onset was 14.3±13.6 years-old, while the duration of the epilepsy disease was 20.4±13.1 years (mean±SD). Additional information can be found in Tables 1, 2, 4.
8123-111462-02 SEEG implantation and localization. [0109] The number and location of SEEG electrodes implanted was pre-operatively planned individually for each patient as part of their clinical care and was not influenced by this study. The implant procedure was performed with robotic stereotactic guidance (ROSA, Zimmer-Biomet, Warsaw, IN, USA), applying bone fiducial registration with accuracy <0.5 mm). Overall, we implanted a total of 5214 contacts (Microdeep® SEEG Electrodes, 12 to 18 channels, DIXI Medical, Marchaux-Chaudefontaine, France), with an average per patient of 200.53±27.87. To target the thalamic nuclei of interest, the following stereotactic coordinates were used: 1) for PUL, in relation to the AC/PC reformatted planes, and having the PC (posterior commissure) as the reference point, coordinates are X: 2-10 mm lateral to the midline plane; Y: 0 to -6 mm posterior to PC; Z: 0 to -6 mm below the AC/PC defined horizontal plane; 2) for ANT, in relation to the AC/PC reformatted planes, and having the MC (mid commissural point) as the reference point, coordinates are X: 6-8 mm lateral to the midline plane; Y: 6 to 7 mm anterior to the MC; Z: 2 to 4 mm above the AC/PC defined horizontal plane; 3) for VIM/VOP, lateral (from about 5 to about 15 mm lateral to the AC/PC line); anterior/posterior (from about 2 to about 10 mm anterior to PC); and dorsal/ventral (from about +1 to about -2 mm from the AC/PC plane. [0110] To reconstruct the position of the SEEG electrode, CURRY software (Compumedics NeuroScan, Hamburg, Germany) was used. First, key reference points on each pre-implantation MRI T1 scan were marked (namely the AC, PC and the nasion). These images were then co-registered with post-implantation CT, and a clinical team member manually identified and labeled all the SEEG contacts from the CT. All the contact locations of the subject MRI were visually inspected and confirmed by a certified neurosurgeon (JGM). [0111] For all subject-analysis (Figure 4b), the electrode coordinates in the subject space MRI were then translated to coordinates in MNI space for each patient. To confirm the contact location within the thalamic nuclei of interest The Human Motor Thalamus Atlas was used (Ilinsky, I. et al. Human Motor Thalamus Reconstructed in 3D from Continuous Sagittal Sections with Identified Subcortical Afferent Territories. eNeuro 5, ENEURO.0060-18.2018, 2018). The assessment of SOZ contacts (as well as non-SOZ contacts used in the following analysis) was confirmed by an experienced neurosurgeon (Table 3). SEEG recording and stimulation. [0112] SEEG data were recorded with Natus Quantum System EEG diagnostic and monitoring system (Natus, Pleasanton, A, USA), with a sampling rate of 2048 Hz (for S26
8123-111462-02 the sampling rate was 1024 Hz) during the extra-operative monitoring at the Epilepsy Monitoring Unit of the University of Pittsburgh Medical Center (Presbyterian Hospital). For all analysis, SEEG bipolar montage was applied to increase spatial selectivity and reduce noise levels. To deliver electrical stimulation in the thalamic contacts, the Nicolet Cortical Stimulator (Natus, Pleasanton, A, USA) was used, which delivers biphasic pulses up to 100 Hz (amplitude was set to 1-3 mA and pulse duration to 60-300 μs for all patients) with bipolar electrode configuration. High-Definition Fiber Tracking. [0113] To estimate anatomical projections from the thalamus to various cortical areas, High-Definition Fiber Tracking (HDFT) of diffusion MRI data was first performed. The diffusion images were acquired on a SIEMENS Prisma Fit scanner using a diffusion sequence (2mm isotropic resolution, TE/TR= 99.2 ms/2490 ms, 257 diffusion sampling with maximum b-value 4010 s/mm²). Diffusion tensor estimation and tractography were performed using DSI studio (http://dsi,studio.labsolver.org). The accuracy of b-table orientation was examined by comparing fiber orientations with those of a population- averaged template. The tensor metrics were calculated using DWI with b-value lower than 1750 s/mm². For fiber tracking, a tracking threshold of 0, angular threshold of 0, and a step size of 0 mm was used. Seed regions in thalamus were utilized to create white matter tracts to regions of interest in the cortex. Seed regions were selected in ANT, VIM/VOP, PUL, and CM based on the extended Human Connectome Project multimodal parcellation atlas. Regions of interest were selected in the frontal lobe, rolandic area, parietal lobe, occipital lobe, and temporal lobe. Tracks with lengths shorter than 30 mm or longer than 1000 mm were discarded. A total of 10,000 tracts were placed. Topology informed pruning was applied to the tractography with 2 interactions to remove false connections. The volume of white matter tracts projecting from each thalamic nucleus to each cortical area was quantified. The volume of each white matter projection was normalized by the total volume projections from each thalamic nucleus (Figure 5a-5b, Figure 10a-10b). Thalamocortical evoked potentials. [0114] In order to confirm the anatomical organization of thalamocortical fibers with electrophysiological techniques, thalamocortical evoked potentials were elicited by thalamic stimulation of PUL, ANT and VIM/VOP (frequency=1 Hz, amplitude=1-3 mA, pulse width=300 μs) and recorded from all available SEEG channels with Natus recording system.
8123-111462-02 SEEG intracerebral data from all cortical channels were filtered with a band-pass Butterworth 2nd order filter (1-1000 Hz) and DC offset was removed from all recordings. From each stimulation pulse, 520 ms epochs (20 ms prior and 500 ms after the stimulus) and computed stimulation triggered averages were extracted. Each epoch was baseline corrected with the pre-stimulus interval. The peak-to-peak amplitude of evoked potentials in each epoch were calculated as the difference between the maximum and minimum voltage value observed within the first 400 ms from the stimulus. This analysis was performed for all available channels that presented sufficient signal to noise ratio, that were located in the regions of interest for this study (not in thalamus) and that were not located in the white matter (Figure 6d-6l). Acquisition and analysis of spontaneous seizures. Spontaneous seizures acquisition [0115] During the extra-operative monitoring, 216 spontaneous seizures were recorded from 23 patients. The remaining 3 (S14, S16, S19) patients either presented technical problems that invalidated the inclusion of the seizures or did not present any spontaneous events during the hospitalization. For this analysis, recordings were collected from 2 minutes before the seizure onset up to 30 seconds after the seizure termination. These time events (onset and termination) were manually marked for each event by certified medical personnel. Such markers were used to define 5 epochs of interested, used in subsequent analysis: 1) baseline (corresponding to 20 seconds occurring two minutes before the seizure onset); 2) seizure initiation (including the 10 seconds preceding the first appearance of a tonic discharge in the SOZ contacts); 3) seizure termination (including the last 10 seconds of discharge); 4) middle of seizure (as the epoch between the previous two intervals 5) total seizure duration (defined as the interval between onset and termination). Non-linear correlation analysis [0116] For each recorded seizure, the h2 non-linear correlation coefficient, as implemented in Anywave (Colombet, B., Woodman, M., Badier, J. M. & Bénar, C. G. AnyWave: a cross-platform and modular software for visualizing and processing electrophysiological signals. J. Neurosci. Methods 242, 118–126, 2015) for each pair of thalamus-SOZ bipolar contacts was computed. The h2 coefficient between two signals is a time-resolved measure of their non-linear dependence. The coefficient was computed over a 2 s time window sliding by steps of 1 s. the h2 across the full SEEG spectrum (1-500 Hz) was
8123-111462-02 computed, as well as separate frequency bands: delta (1-4 Hz), theta (4-8 Hz), alpha (8-15 Hz), beta (15-30 Hz), gamma (30-45 Hz), gamma2 (55-90 Hz), ripple (80-250 Hz), fast ripple (250-500 Hz). For each time interval of interest (seizure duration, seizure initiation, middle of seizure, seizure termination), the mean h2 was computed (Figure 6b, 6e, 6f). [0117] To computer the change in h2 between matched and unmatched nuclei (Figure 6g), the percentage increase of h2 in the seizure duration with respect to the baseline epoch was calculated for each matched and unmatched pair as: ℎ2 ^ℎ^^^^(%) = 100 ∗ (^^^^(ℎ2^^^^^^^) − ^^^^(ℎ2^^^^^^^^))/^^^^(ℎ2^^^^^^^^) % [0118] The subtraction between the percentage h2 changes calculated in matched thalamus-SOZ and unmatched thalamus-SOZ pairs was then performed [0119] For the correlation between the thalamus and non-SOZ regions, two seizures for each patient were randomly selected. The mean h2 of the thalamus with 3 distinct non-SOZ pair of contacts were computed (Table 3). Granger Causality analysis [0120] To analyze the directionality of the interactions between the thalamus and the cortex, the Granger Causality method was used (Granger, C. W. J. Investigating Causal Relations by Econometric Models and Cross-spectral Methods. Econometrica 37, 424–438, 1969). First, all the seizures that lasted at least 10 s and showed an increase in the h2 correlation coefficient in the theta to beta band were selected. The raw SEEG signals in the 4-30 Hz range were filtered and each seizure recording was divided in 10 s non-overlapping windows. The GC matrix of each matched thalamus-SOZ pair for every epoch was computed. This computation results in a 4x4 matrix for each epoch, where the second diagonal contains the thalamocortical (th→SOZ) and corticothalamic (SOZ→th,) GC value. In addition to the absolute GC value, per percentage change in GC from initiation to termination was quantified (Figure 4 c, d, f) as: ^^^ (%) = 100 ∗ (^^ ^^!^^^ ^"^ − ^^^^^ ^^ ^"^)/^^^^^ ^^ ^"^) % where termination and initiation are the 10 seconds epochs preceding the seizure onset and the seizure termination time stamps, respectively. In a total of 20 patients, 17 showed an increase in the proportion of seizures with the thalamus leading at termination and 18 showed higher ^^^ in the thalamocortical (and not corticothalamic) coefficient. Such finding robustly confirms population-observed trends.
8123-111462-02 Case report: CM connectivity in generalized epilepsy [0121] The exclusion of the CM in this study (Figure 10), focused on focal epilepsy, was justified by performing structural and functional connectivity analysis of the CM, as well as the PUL, ANT and VIM/VOP on a patient affected by generalized epilepsy. In particular, the patient was a female in her late 20s, with a severe medically refractory epilepsy, with more than 10 generalized seizures per day. The patient underwent SEEG exploration to investigate the appropriate thalamic target for neuromodulation as a part of her clinical care. [0122] h2 correlation analysis was performed for 24 seizures recorded with simultaneous sampling of CM, PUL, ANT, VIM/VOP as well as 13 bipolar electrodes sampling the following brain structures: insula, frontal operculum, superior temporal sulcus, superior temporal gyrus, middle temporal gyrus. The mean h2 coefficient was computed for each thalamic nucleus with the cortical electrodes. Unlike the focal epilepsy patients, where the SOZ only comprises a pair of cortical electrodes, here the h2 values of each thalamus-cortex pair was averaged. High-frequency acute thalamic stimulation. Stimulation testing and protocol [0123] During post-operative monitoring in the EMU, acute thalamic stimulation testing was performed on 14 patients. Both matched and unmatched thalamic nuclei were stimulated. Continuous electrical stimulation was applied with bipolar configuration on the thalamic site of interest, at a frequency of 100 Hz. The amplitude and pulse width were adjusted individually for each patient according to their comfort levels, but did not exceed the ranges of 1-3 mA and 60-300 us respectively. [0124] For clinical safety reasons, the stimulation testing occurred only after the patients exhibited spontaneous seizures and in seizure-free days. The duration of the stimulation train varied from a minimum of 5 seconds to a maximum of 30 seconds, repeated over 1-10 times depending on the patient comfort and clinical state. Preprocessing and IED detection [0125] To analyze the immediate effect of thalamic stimulation the following data was extracted: i) for baseline (Stim OFF), 2 minutes of interictal activity in the SOZ channels before any kind of stimulation was delivered to the patient was collected; ii) for active stimulation period (Stim ON), the SOZ recording for the whole duration of stimulation up to
8123-111462-02 10 s after stimulation was stopped was included (Ikegaya, N. et al. Thalamic stereoelectroencephalography for neuromodulation target selection: Proof of concept and review of literature of pulvinar direct electrical stimulation. Epilepsia 65, e79–e86, 2024). The first two seconds after the stimulation was delivered was excluded to reduce false positive detection due to transient stimulation-induced burst (Milosevic, L. et al. Physiological mechanisms of thalamic ventral intermediate nucleus stimulation for tremor suppression. Brain 141, 2142–2155, 2018). For technical reasons, 4 patients had a shorter baseline period (average of 45 s). Prior to epoching, the data in Anywave (Colombet, B., Woodman, M., Badier, J. M. & Bénar, C. G. AnyWave: a cross-platform and modular software for visualizing and processing electrophysiological signals. J. Neurosci. Methods 242, 118–126, 2015) was preprocessed by applying a band-pass filter (1-1000 Hz) and a notch filter (60Hz) and manually removing channels affected by stimulation artifact or other noise sources. On the remaining channels, independent component analysis (ICA) was applied and n components extracted (where n=number of channels -1). This method is a common technique used to separate independent sources linearly mixed in several sensors. All the components were visually inspected and the ones associated with stimulation artifacts were rejected. In this way, an automatic spikes detection algorithm on the stim ON and stim OFF recordings was then applied. [0126] Each intracranial recording of interest was then divided in 5 s non-overlapping epochs, on which the detection of epileptiform discharges was computed. To avoid any confound due to the stimulation artifact, interictal spikes were considered as IED, and not high-frequency oscillations. For this, Delphos software was used which detects interictal spikes from SEEG recording from their time-frequency representation (see Roehri, N., Lina, J.-M., Mosher, J. C., Bartolomei, F. & Benar, C.-G. Time-Frequency Strategies for Increasing High-Frequency Oscillation Detectability in Intracerebral EEG. IEEE Trans. Biomed. Eng. 63, 2595–2606, 2016; Roehri, N., Pizzo, F., Bartolomei, F., Wendling, F. & Bénar, C.-G. What are the assets and weaknesses of HFO detectors? A benchmark framework based on realistic simulations. PLOS ONE 12, e0174702 (2017). This detector was previously demonstrated to allow for almost 100% specificity and more than 80% sensitivity. To ensure correct spikes detection, the following occurred 1) computed the analysis also on non-SOZ channels, to confirm that no spikes would be detected, and 2) visually inspected the data. the IED number for each Stim ON and Stim OFF epoch was saved.
8123-111462-02 IED analysis [0127] To quantify the impact of acute thalamic stimulation on the IED rate, two complementary analyses were computed, based on the data quality: a) if the IED were clearly detectable and frequent (occurring in at least 50% of the baseline epochs), the IED rate was calculated as the number of IED per minute, in each Stim ON and Stim OFF epoch; b) if more than half of the baseline epochs presented no IED, the probability of finding no spikes across all the Stim ON and Stim OFF epochs was calculated (Table 2). Even if consistent spiking was observed in baseline epochs, we included in analysis b also a subject (S26) that presented complete suppression of IEDs in stimulation epochs, hence precluding statistical analysis. For both analyses, we computed the percentage difference of these quantities for Stim ON vs stim OFF to characterize the stimulation effect. A beneficial effect of stimulation on epileptiform discharges would result in a smaller IED rate with stimulation ON for analysis a, and a positive change in analysis b, prompting to show that stimulation epochs would more likely show complete suppression of IED. Clinical outcome of chronic thalamic stimulation. [0128] The clinical outcome of hodologically matched PUL and ANT stimulation in seven individuals (S16, S27-S32) who received a chronic neuromodulation system as part of their clinical care was retrospectively evaluated. [0129] Demographics and epilepsy information for these patients is reported in Table 1. All patients received a bilateral implant of the PUL or ANT, according to their SOZ location and as indicated by their clinical team following SEEG monitoring. Six patients received a Responsive Neurostimulator (RNS), while one patient received a DBS system (Medtronic Percept). Stimulation parameters were individually tailored for each patient according to their clinical need (Table 4). No clinical decisions were based upon this research. [0130] The percentage reduction in disabling seizures’ frequency and the change in antiseizure medication was retrospectively evaluated. The follow-up window ranged from 9 to 30 months. Data analysis and statistical procedures. [0131] All figures and analysis were performed using Matlab 2023b (Mathworks, California, US). For all box plots reported in this manuscript, the whiskers extend to the maximum spread not considering outliers, central, top, and bottom lines represent median, 25th, and 75th percentile, respectively.
8123-111462-02 [0132] For all the analysis, the bootstrap method was used, which does not rely on distributional assumptions of the data, but rather resamples the quantities of interest to achieve empirical confidence intervals. For each comparison, a bootstrap sample was created (for n=10000 repetitions) by drawing a sample with replacement from the actual data points (n=10000 repetitions), and calculated the difference in means of the resampled data. Two-tailed bootstrapping was then applied with significance levels of 0.05 (95% confidence interval), 0.01 (99% confidence interval), or 0.001 (99.9% confidence interval). The null hypothesis of no difference in the mean was rejected if 0 was not included in the confidence interval of the corresponding alpha value. If multiple comparisons were performed at once, a Bonferroni correction was used by dividing the alpha value by the number of pairwise comparisons being performed. [0133] It will be apparent that the precise details of the methods or compositions described may be varied or modified without departing from the spirit of the described implementations. We claim all such modifications and variations that fall within the scope and spirit of the claims below.