WO2002065906A2 - Dispositif et procede permettant de realiser des etudes de conduction nerveuse avec localisation des reponses declenchees - Google Patents

Dispositif et procede permettant de realiser des etudes de conduction nerveuse avec localisation des reponses declenchees Download PDF

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Publication number
WO2002065906A2
WO2002065906A2 PCT/US2002/004204 US0204204W WO02065906A2 WO 2002065906 A2 WO2002065906 A2 WO 2002065906A2 US 0204204 W US0204204 W US 0204204W WO 02065906 A2 WO02065906 A2 WO 02065906A2
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WO
WIPO (PCT)
Prior art keywords
anatomical site
detector
nerve
stimulator
stimulus
Prior art date
Application number
PCT/US2002/004204
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English (en)
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WO2002065906A9 (fr
WO2002065906A3 (fr
Inventor
Shai N. Gozani
Ann Pavlik Meyer
Xuan Kong
Martin D. Wells
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Neurometrix, Inc.
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Priority to EP02714878A priority Critical patent/EP1367939A4/fr
Publication of WO2002065906A2 publication Critical patent/WO2002065906A2/fr
Publication of WO2002065906A3 publication Critical patent/WO2002065906A3/fr
Publication of WO2002065906A9 publication Critical patent/WO2002065906A9/fr

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/103—Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
    • A61B5/11—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb
    • A61B5/1104—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb induced by stimuli or drugs
    • A61B5/1106—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb induced by stimuli or drugs to assess neuromuscular blockade, e.g. to estimate depth of anaesthesia
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/25—Bioelectric electrodes therefor
    • A61B5/279—Bioelectric electrodes therefor specially adapted for particular uses
    • A61B5/296—Bioelectric electrodes therefor specially adapted for particular uses for electromyography [EMG]
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/40—Detecting, measuring or recording for evaluating the nervous system
    • A61B5/4029—Detecting, measuring or recording for evaluating the nervous system for evaluating the peripheral nervous systems
    • A61B5/4041—Evaluating nerves condition
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
    • A61B2562/06—Arrangements of multiple sensors of different types
    • A61B2562/063—Arrangements of multiple sensors of different types in a linear array
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
    • A61B2562/16—Details of sensor housings or probes; Details of structural supports for sensors
    • A61B2562/166—Details of sensor housings or probes; Details of structural supports for sensors the sensor is mounted on a specially adapted printed circuit board
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/6813—Specially adapted to be attached to a specific body part
    • A61B5/6829—Foot or ankle

Definitions

  • This invention relates to apparatus and methods for the assessment of neuromuscular function. More specifically, this invention relates to apparatus and methods for diagnosing peripheral nerve and muscle diseases based on the assessment of neuromuscular function.
  • Neuromuscular diseases which represent disorders of the peripheral nerves and muscles, are a common and growing health care concern.
  • the most prevalent neuromuscular disorders are carpal tunnel syndrome (CTS)/ low back pain caused by spinal root compression (i.e., radiculopathy) , and diabetic neuropathy, which is nerve degeneration associated with diabetes.
  • CTS carpal tunnel syndrome
  • radiculopathy spinal root compression
  • diabetic neuropathy which is nerve degeneration associated with diabetes.
  • the effective prevention of neuromuscular dysfunction requires early detection and subsequent action. Even experienced physicians find it difficult to diagnose and stage the severity of neuromuscular dysfunction based on symptoms alone. The only objective way to detect many neuromuscular diseases is to measure the transmission of neural signals.
  • the gold standard approach is a formal nerve conduction study by a clinical neurologist, but this procedure has a number of significant disadvantages. First, it requires a highly trained specialist. As a result, it is expensive and generally requires weeks or months to complete. Second, because they are not readily available, formal nerve conduction studies are generally performed late in the episode of care, thus serving a confirmatory role rather than a diagnostic one.
  • both systems suffer from several significant disadvantages, however.
  • First, both systems are large, bulky, and constructed from rigid structures that create a supporting fixture for the arm and hand of an adult. This severely limits their portability and increases their cost.
  • Second, these systems are only applicable to specific limbs and are not generally applicable to numerous anatomical sites.
  • Third, these devices require highly trained operators who can make the appropriate adjustments on the apparatus so as to ensure electrode contact with the proper anatomical sites on the arm and hand. In particular, these systems provide no physiological localization of the electrodes, and as a result multiple placements are often required to find the correct electrode location.
  • the present invention avoids the aforementioned limitations .
  • an apparatus and method are provided for the substantially automated, rapid, and efficient assessment of neuromuscular function without requiring the involvement of highly trained personnel.
  • the assessment of neuromuscular function is effected by stimulating a nerve, and then measuring the response of a muscle innervated by that nerve.
  • the muscle response is detected by measuring the myoelectric potential generated by the muscle in response to the stimulus.
  • the apparatus and method of the invention assess physiological function in, for example, the lower extremity of an individual by using an electrode to apply a stimulus to a nerve.
  • the stimulus may be, for example, an electrical stimulus or a magnetic stimulus. Other types of stimuli may also be used.
  • a detector adapted for detecting the myoelectric potential generated by a muscle in response to the stimulus, detects the response of the muscle to the stimulus.
  • An electronic controller then evaluates the physiological function of the nerve. The function is then correlated to the presence or absence of a neuromuscular pathology, such as, for example, Carpal Tunnel Syndrome (CTS) or lumbosacral radiculopathy.
  • CTS Carpal Tunnel Syndrome
  • lumbosacral radiculopathy lumbosacral radiculopathy.
  • a sensor including a stimulator electrode and a myoelectric detector.
  • the stimulator electrode is adapted for placement at a first anatomical site substantially adjacent to a nerve
  • the myoelectric detector is adapted for placement at a second- anatomical site substantially adjacent to a muscle innervated by that nerve.
  • a semi- flexible connector links the stimulator electrode and myoelectric detector such that the connector automatically positions the myoelectric detector at the second anatomical site when the stimulator electrode is positioned at the first anatomical site, or vice versa.
  • the apparatus of the invention further includes a processor for processing at least one signal detected by the myoelectric detector which is characteristic of the second anatomical site.
  • the physiological function of an individual which is to be assessed by the apparatus of the invention is nerve conduction, such as conduction of the tibial nerve or the peroneal nerve.
  • the first anatomical site is a superficial' location over the peroneal nerve and the second anatomical site is a superficial location over the extensor digitoru brevis muscle of the foot.
  • the first anatomical site is a superficial location over the tibial nerve and the second anatomical site is a superficial location over the abductor hallucis muscle of the foot.
  • the sensor of the invention includes a positioning indicator for location over a third anatomical site such as the medial or lateral malleolus of the individual.
  • the superficial location is on the skin of the individual.
  • the flexible connector is a strip which is rectangular, s-shaped, or any other shape configured to position the myoelectric detector over the second anatomical site when the stimulator electrode is positioned over the first anatomical site.
  • the connector includes electrical traces for carrying signals to the stimulator electrode, and from the myoelectric detector, to an electronic controller and monitor. In one embodiment, the traces connect the stimulator electrode and the myoelectric detector to the controller.
  • the myoelectric detector includes an electrode array that includes at least two independent interleaved bipolar recording electrodes.
  • the signals recorded from the recording electrodes include compound muscle action potentials (CMAP's) .
  • CMAP compound muscle action potential
  • the detectable signal includes the weighted sum of the recordings of at least two of the recording electrodes.
  • the method of the invention relates to the assessment of physiological function using appropriate apparatus.
  • a sensor including a stimulator electrode and a myoelectric detector, attached by a connector, is placed on the skin of the individual overlying the anatomical location to be studied.
  • the stimulator electrode is placed at the first anatomical site.
  • the myoelectric detector is automatically positioned at the second anatomical site by the construction of the connector.
  • the stimulator electrode applies a stimulus to a nerve (for example, the peroneal nerve or the tibial nerve) .
  • a nerve for example, the peroneal nerve or the tibial nerve
  • a muscle innervated by the nerve for example, the extensor digit ⁇ rum brevis muscle of the foot with respect to the peroneal nerve, or the abductor hallucis muscle of the foot with respect to the tibial nerve
  • the signal generated by the myoelectrical potential is detected by the electrode array of the myoelectric detector and processed by the processor in communication with the myoelectric detector.
  • the processor processes the signals from the myoelectric detector' s electrode array to select which electrode (s) of the electrode array is detecting at least one signal characteristic of the second anatomical site.
  • the electrode selected by the processor as detecting at least one signal characteristic of the second anatomical site is used to perform nerve conduction studies to assess physiological function of the individual.
  • the processor further processes signals from the selected electrode to perform the nerve conduction study. The processed signals are correlated to physiological function of the nerve and muscle .
  • Fig. 1 illustrates one embodiment of a sensor formed in accordance with the present invention placed on the lower extremity of an individual
  • Fig. 2 illustrates one embodiment of a sensor formed in accordance v ⁇ ith the present invention shaped to fit the foot of an individual;
  • Fig. 2A is a cross-sectional view illustrating one way of fabricating the sensor of the present invention
  • Fig. 3 illustrates the embodiment of Fig. 2 positioned on the foot of a patient
  • Fig. 4 is a graph in the time domain of the muscle response evoked and measured by an embodiment of the present invention.
  • Fig. 5 is a flowchart illustrating the steps in one embodiment of the invention to select optimum recording electrode pairs
  • Fig. 6 is a graph in the frequency domain showing the power spectral density of muscle responses evoked and measured by one embodiment of the invention. Detailed Description Of The Preferred Embodiments
  • a primary objective of the present invention is to measure evoked potentials in peripheral nerves and muscles.
  • the process of acquiring such measurements is commonly described as a nerve conduction study.
  • Typical nerve conduction measurements include nerve impulse propagation latency (distal motor latency, DML, or distal sensory latency, DSL) , nerve impulse velocity (conduction velocity, CV) , the amplitude of the evoked neural signal (nerve action potential, NAP, amplitude), and the amplitude of the neurally evoked muscle signal (compound muscle action potential, CMAP, amplitude) .
  • the present invention includes a nerve conduction sensor and associated algorithms. Taken together, the invention provides mechanical and electronic localization to perform accurate and reliable nerve conduction studies.
  • Mechanical localization is a process whereby mechanical means facilitate the placement of an evoked response detector in the general vicinity of the nerve "segment or muscle to be measured. Subsequently, electronic localization may be utilized to precisely investigate the electrophysiological properties of the region and identify the optimal location at which to measure the evoked response, so as to obtain accurate and reliable measurements.
  • the present invention obviates the need for precise electrode placement and knowledge of neuroanatomy. Instead, this knowledge is effectively encapsulated within the mechanical and electronic localization means, thereby allowing an effective nerve conduction study to be performed without requiring the involvement of highly trained personnel.
  • a nerve conduction sensor 5 formed in accordance with the present invention.
  • Sensor 5 comprises a stimulator 10, a detector 15, a connector 20, and an interface 25, all integrated in a unitary housing.
  • the stimulator 10 stimulates " a ' peripheral nerve N at a first anatomical site Si, for example, the ankle.
  • the detector 15 detects an evoked signal at a second anatomical site S2, which is either the nerve N stimulated by the stimulator 10 at a location different from the first anatomical site SI or, as shown in Fig. 1, on a muscle M innervated by the stimulated nerve N, for example, the extensor digitorum brevis muscle.
  • first anatomical sites SI for example, knee, wrist, and elbow
  • second anatomical sites S2 for example, foot, hand, and calf
  • the connector 20 which connects the stimulator 10 and the detector 15.
  • the connector 20 automatically positions the detector 15 substantially adjacent to the second anatomical site S2 when the stimulator 10 is positioned at the first anatomical site SI, thus mechanically localizing the evoked signal.
  • the detector 15 preferably contains an element array 30 (Fig. 2) comprising a plurality of individual detection elements.
  • the evoked response detected by the detector 15 is measured using one or more of the detection elements of the element array 30, thus electronically localizing the evoked signal.
  • Fig.- 2 provides a detailed view of one embodiment of the nerve conduction sensor 5, which includes the stimulator 10, detector 15, connector 20, and interface 25.
  • the nerve conduction sensor 5 is formed from multiple layers of materials.
  • the primary base layer is preferentially formed from a continuous sheet of MYLAR.
  • Subsequent layers include colored ink, conductive silver traces, insulating material, silver-chloride pads, hydrogel, and medical grade adhesive.
  • the sensor is then applied to the skin of the individual so that the operative elements face inwardly, toward the patient, and so that the base layer faces outwardly, away from the patient. Details of the general construction of such layered sensors are known in the art.
  • the connector 20 of the nerve conduction sensor 5 is configured to mechanically orient the stimulator 10 and the detector 15 relative to one another and the patient's anatomy.
  • the connector 20 ensures that placement of stimulator 10 at a first anatomical site SI, substantially determines the orientation and position of the detector 15 at a second anatomical site S2 as illustrated in Fig. 1-.
  • the automatic positioning of the detector 15 need not be precise but must be substantially in the vicinity of the second anatomical site S2.
  • the construction of connector 20 substantially limits the range of anatomic sites over which the detector.15 can be placed, so that anatomic sites that are physiologically unrelated to the stimulation site Si (e.g., anatomical site S3 in Fig 1.) are not accessible to the detector 15.
  • the connector 20 is formed from MYLAR. However, other materials such as various plastics may also be used.
  • the particular connector configuration shown in Fig. 2 is intended to be illustrative and other configurations may also be used and should be considered to be within the scope of the present invention.
  • the stimulator 10 and the detector 15 are contiguous and attached. The construction of connector 20 is limited only by" the objective that placement of the stimulator 10 at the first anatomical site SI automatically places the detector 15 substantially adjacent to the second anatomical site S2. The converse will also hold, i.e., placement of the detector 15 at the second anatomical site S2 automatically places the stimulator 10 at the first anatomical site SI.
  • the stimulator 10 includes at least one stimulation element 35 (Fig. 2) that delivers a stimulus to a peripheral nerve.
  • the stimulus can be electrical, magnetic, optical, chemical, or biological.
  • the stimulus is an electrical impulse and the stimulation element 35 includes a plurality of layers of different materials which together form the stimulation electrode.
  • stimulation electrode 35 may include a mylar substrate 40, a layer, of conductive ink 45, a conductive gel 50 bordered by a foam mask 55, a layer ' of adhesive 60, and a release liner 62.
  • the stimulator 10 includes a temperature probe 65.
  • the temperature probe comes into contact with the test subject's skin and measures the skin surface temperature. This temperature is then used for calibrating the system.
  • Other locations for the temperature probe 65 have been contemplated and include sites within the detector 15 and the connector 20.
  • the detector 15 includes an array 30 of detection elements.
  • the detection elements may be capable of detecting bioelectrical, magnetic, optical, chemical or biological signals.
  • bioelectrical signals, and more specifically biopotentials are detected, and the array 30 includes at least four electrodes 70, 75, 80 and 85 (collectively, the array 30) , preferably arranged in a linear configuration such as shown in Fig. 2.
  • the array 30 includes at least four electrodes 70, 75, 80 and 85 (collectively, the array 30) , preferably arranged in a linear configuration such as shown in Fig. 2.
  • other configurations such as a matrix of electrodes, and different numbers of electrodes, have been contemplated and should be considered within the scope of the present invention.
  • the detector array 30 illustrated, for example, in Fig. 2 allows the detector 15 to adapt to variations in the anatomic location, physical structure and physiological organization of the second anatomical site S2, such as a muscle M.
  • the electrodes 70, 75, 80 and 85 are composed of a plurality of layers of different materials with substantially the same area. Again, a construction such as that shown in Fig. 2A may be used. In many applications, such as in the recording of electrical signals, a distinct reference electrode is required. This reference electrode essentially establishes a "zero point" that other voltages may be referenced against.
  • Such a reference electrode 90 is shown in Fig. 2.
  • the reference electrode 90 provides a reference voltage for acquisition of biopotentials signals from detector array 30 of the detector 15.
  • the reference electrode 90 is located on the stimulator 10. In other embodiments, the reference electrode 90 is located on the detector 15, on the connector 20, or on another part of the nerve conduction sensor 5.
  • the stimulator electrode 10 and the bioelectrical detector 15 are formed in the nerve conduction sensor 5 so as to make contact' with the skin of the individual when the nerve conduction sensor 5 is in position on the individual.
  • the nerve conduction sensor 5 may be configured for different sizes (e.g., small, medium and large), for different nerves (e.g., median, ulnar, peroneal, and posterior tibial nerves), for different muscles (e.g., extensor digitorum brevis, adductor hallucis brevis) , for right and left anatomical sites, and for various anatomical sites (e.g. , ' ankle, foot, hand, wrist).
  • the nerve conduction sensor 5 has an interface 25 that serves as a communications port between the nerve conduction sensor 5 and external devices, such as an electronic controller 95 (see Fig. 3) .
  • the nerve conduction sensor 5 also has a series of traces that provide communication between the connector 25 and internal elements of the sensor. In a preferred embodiment, illustrated in Fig. 2, these traces 100, 105, 110 and 115 are capable of transmitting electronic signals and are embedded within a unitary housing of sensor 5. As shown in Fig.
  • the nerve conduction sensor 5 includes traces 100 that communicate signals from the stimulation elements 35 on the stimulator 10 to the connector 25; traces 105 that communicate signals from the element array 30 on the detector 15 to the connector 25; traces 110 that communicate signals from the reference electrode 90 to the connector 25; and traces 115 that communicate electronic signals from the temperature probe 65 to the connector 25.
  • the traces are created by printing silver lines 45 (Fig. 2A) on the mylar substrate 40 which are in direct communication with conductive gels 50 at both the stimulation and detection sites.
  • the foam mask 55 is positioned on top of these traces to prevent shorting.
  • the nerve conduction sensor 5 includes indicators 120 and 125 to aid in positioning the sensor on the individual's extremity.
  • the nerve conduction sensor 5 includes positioning indicators . 120 and 125 to help place the stimulator 10 correctly; connector ' 20 then ensures that detector 15 is positioned appropriately.
  • another positioning indicator 130 helps place the detector 15 correctly; connector 20 then ensures that stimulator 10 is positioned appropriately.
  • indicators 120, 125 and 130 are all provided on a sensor 5.
  • the positioning indicators 120, 125 and 130 are placed on the skin of the individual at particular anatomical sites, thereby aiding in the placement and orientation of the nerve conduction sensor 5 on the extremity of the individual.
  • the positioning indicators 120, 125 and 130, shown in Fig. 2 are merely illustrative and other embodiments with various positioning indicators and mechanisms known to the skilled person are contemplated by the invention.
  • the nerve conduction sensor 5 is interfaced to an electronic controller 95.
  • the electronic controller 95 includes a generator to generate electrical stimuli that stimulate the nerve N through the stimulator 10, a signal detector to detect signals from a nerve N or muscle M (evoked by stimulation by the stimulator 10) through the detector 15, a processor to process the detected signals, and a display to communicate the results to an operator or another electronic device such as a computer.
  • the electronic controller 95 includes a ⁇ controller detector to detect the evoked response from detector 15 and a transmitter to transmit this information to a remote processor for further processing and analysis. This transmitter may be telephone lines, the Internet, or wireless networks.
  • the electronic controller 95 includes an amplifier to amplify, a recorder to record, and a processor to process bioelectrical signals generated by detector 15.
  • One embodiment of the controller 95 contains two differential amplifiers each of which is connected to two electrodes within the electrode array 30.
  • one differential amplifier is electronically connected to electrodes 70 and 80, through connector 25 and traces 105
  • another differential amplifier is electronically connected to electrodes 75 and 85, through connector 25 and traces 105.
  • This configuration thus represents two differential bipolar recordings.
  • Other configurations by which the electrodes 30 are connected to the amplifier have been contemplated and should be considered within. the scope of the present invention.
  • the invention is a method for performing nerve conduction studies.
  • motor nerve conduction studies may be performed with the nerve conduction sensor 5. This is accomplished by placing the stimulator electrode 10 of the sensor 5 over the nerve N to be studied, for example the peroneal nerve at the ankle.
  • the connector 20 of the sensor 5 then automatically places the detector 15 substantially adjacent to a muscle M innervated by the nerve N, for example the extensor digitorum brevis muscle on the lateral aspect of the mid foot. After the detector 15 is put in contact with the individual's skin, one or more of the detection electrodes in array 30 are selected, preferably according to an algorithm described below and illustrated in Fig. 5.
  • the motor nerve conduction study is thus carried out by repeatedly stimulating the nerve N and recording the resulting evoked responses by the chosen detection electrodes in array 30.
  • the evoked response thus detected provides information on the function of the nerve and muscle and may include the distal motor latency (DML) , the compound action potential (CMAP) amplitude, the F-wave latency, the F-wave amplitude, the refractory period, the activity dependence, the stimulation threshold, and other nerve conduction parameters familiar to those knowledgeable in the art.
  • DML distal motor latency
  • CMAP compound action potential
  • the particular detection electrodes in array 30 do not need to be constant throughout the nerve conduction study. In other words, some of the detection electrodes can be used in one part of the study, and other electrodes can be used in a different part of the study.
  • the electronic controller 95 (Fig. 3) and the nerve conduction sensor 5 are configured so that the electronic controller acquires two signals formed from two interleaved pairs of detection electrodes in array 30. Signals thus recorded are called bipolar signals.
  • An embodiment of a bipolar signal 135 is illustrated in Fig. 4.
  • the signal 135 has a number of features that are important both for the assessment of nerve conduction parameters ' such as those described above, as well as for the determination of the anatomical and physiological relationship between the detection electrodes and the underlying muscle M.
  • One feature is the latency 140 of the signal.
  • the latency 140 represents the time between the stimulation of nerve N and arrival of the impulse at the innervated muscle M.
  • Latency 140 and its associated parameter velocity, are generally considered to be the most important nerve conduction parameters. In this respect it should be appreciated that diseased nerves have a longer latency than normal nerves. In addition, the specific electrode located closest to the muscle motor point 145 (Fig. 1) will typically have the lowest latency among the electrode array 30.
  • Another feature of the signal 135 is the maximum rising slope 150 of the signal. This parameter represents the depolarization of the muscle tissue M.
  • the maximum rising slope 150 is particularly important because the signal recorded over the motor point 145 (Fig. 1) generally has a larger slope 150 than a biopotential recorded away from the motor point 145.
  • Another feature of the signal 135 is the peak-to- peak amplitude 155 of the signal 135. This parameter represents the overall size of the muscle action potential. This is an important characteristic, inasmuch as diseased nerves typically have a lower amplitude 155 than healthy nerves.
  • signals 135 recorded over the motor point 145 generally have larger peak-to-peak amplitude 155 than those recorded away from the motor point 145.
  • signal 135 should only be considered to be representative of those used to determine nerve conduction and muscle structure. Other features have been contemplated and should be considered within the scope of the present invention.
  • the performance of nerve conduction studies with the nerve conduction sensor 5 requires selection of one or more electrodes from array 30 from which the evoked response is measured and nerve conduction parameters-, such as the distal motor latency, are determined.
  • nerve conduction parameters- such as the distal motor latency
  • the evoked response must be recorded from the motor point - which is the region of the muscle innervated by the nerve.
  • the objective of the electrode array 30 is to provide means for sampling the evoked response from all or a section of the muscle, and to determine the single electrode or combination of electrodes that best represent the evoked response from the motor point.
  • the evoked response is a weighted sum of one or more electrodes.
  • the single electrode that best represents the motor point response is used.
  • Fig. 5 illustrates a preferred algorithm for utilizing the signals 135 recorded from the electrode array 30 to select the optimal electrode (s) 70, 75, 80, 85 for performance of nerve conduction studies.
  • process step 160 two signals S; and S 2 are acquired-.
  • these signals are differentially recorded from two interleaved pairs of electrodes 70, 80, and 75, 85 and typically have a waveform shape and feature set similar to those shown, for example, in Fig. 4.
  • V(Eeo) and S 2 V (E 75 ) -V(E S _) , where V(E X ) is the biopotential at electrode E ⁇ , and E 70 and E 5 form the positive differential inputs and E 80 and E 8 s form the negative differential inputs of their respective signals.
  • V(E X ) is the biopotential at electrode E ⁇
  • E 70 and E 5 form the positive differential inputs
  • E 80 and E 8 s form the negative differential inputs of their respective signals.
  • These signals are only illustrative and embodiments have been contemplated in which different combinations of electrodes are utilized, such as 70, 75, and 80, 85, or 70, 85, and 75, 80, in which each of the electrodes is recorded relative to a common indifferent electrode, and in which the electronic controller 95 has means to dynamically create various combinations of differential recordings.
  • the illustrative algorithm is described in terms of two signals, it can be applied to a greater number of signals formed from recordings of the electrode array 30.
  • predetermined signal features are calculated for each of the two signals S ⁇ and S 2 in process steps 165, 170 and 175.
  • these parameters are independent of the optimal polarity of the signals.
  • the same parameters are calculated for Si and -Si.
  • these parameters are illustrative and additional parameters may be used.
  • the algorithm continues with process step 180, in which the latencies (Li and L 2 ) of the two- signals are compared to determine if they are within a predetermined range, ⁇ , of one another.
  • the predetermined range is between about 0.1 and 0.7 s, preferably 0. ms .
  • a score (fi and f 2 ) is determined for each signal from the non-latency parameters by creating a linearly weighted sum of these parameters using predetermined coefficients. Subsequently, in process step 190, the scores are compared for equality. If they are equal then the algorithm continues with process step 195. If they are not equal then the algorithm continues with process step 200. If the latency difference is not within the predetermined range as determined in step 180, then the algorithm continues with process step 195. In step 195, a score is determined for each signal based entirely on its corresponding latency. In a preferred embodiment, this score is inversely proportional to the latency such that a shorter latency will yield a higher score. As an example, the following scoring function has been contemplated.
  • process step 200 the scores for the two signals (fi and f 2 , regardless of whether calculated in process step 185 or 195) are compared. If the first signal has a greater or equal score to .the second signal, then the algorithm continues with process step 205 in which the first signal is chosen for subsequent processing and then the algorithm proceeds to process step 210. If in process step 200, the first signal has a lower score than the second signal, then the algorithm proceeds to process step 215 in which the second signal is chosen for subsequent processing before continuing with process step 210.
  • process step 210 the latency of the chosen signal (Si if from process step 205 and S 2 if from process step 215) is calculated for each polarity yielding two latencies, L+ and L_.
  • the algorithm then proceeds to process step 220 where the latencies are compared. If the positive polarity latency (L + ) is less than or equal to the negative polarity latency (L_) , then the algorithm proceeds to process step 225 where the optimal recording electrode is reported as the positive input to the differential recording. For example, in the embodiment in which the first signal is formed from a differential recording of electrodes 70 and 80, the reported electrode would be electrode 70.
  • the algorithm proceeds to process step 230 where the optimal recording electrode is reported as the negative input to the differential recording.
  • the optimal recording electrode is reported as the negative input to the differential recording.
  • the reported electrode would be electrode 80.
  • a set of predetermined linear weights is utilized in process step 185 to generate a score indicating which signal is optimal.
  • these weights are obtained by performing a linear regression between an ensemble of signals and an expert's assessment of their optimality.
  • a set of signals is obtained with the nerve conduction sensor and then a neurophysiological expert assigns an optimality score to them.
  • the scoring function is calculated by performing a linear regression between the signals and the expert score.
  • the expert score indicates whether the electrodes from which the signal was obtained are over the muscle motor point.
  • the scoring function is determined by logistic regression analysis.
  • the scoring function is neural network trained by a technique such as backwards propagation.
  • a combination of fuzzy logic and expert system based technique can be used to derive the scoring function.
  • Fig. 6 shows the power spectrum of two bipoloar signals recorded with the nerve conduction sensor 5.
  • the horizontal axis 235 shows frequency.
  • the vertical axis 240 shows the power spectral density, which was calculated by taking the discrete Fourier transform of each signal and then normalizing the spectral energy to the maximum value. This allows the resulting power spectral densities 245 and 250 to be compared.
  • a signal recorded over the motor point 145 will have a simpler morphology than one recorded away from the motor point 145.
  • the signal recorded from the motor point 145 can be determined by that which concentrates more towards lower frequencies.
  • signal 245 has proportionally more energy at lower frequencies than does signal 250.
  • signal 245 is expected -to be closer to the motor point 145.
  • Features derived from other transformations such as wavelet and multi- resolution analysis can also be used to determine motor point.

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Abstract

Dispositif et procédé permettant de détecter une fonction physiologique, par exemple une conduction nerveuse. Selon un mode de réalisation, le dispositif comprend un boîtier renfermant un simulateur dont la forme s'adapte à un premier site anatomique et un détecteur dont la forme s'adapte à un second site anatomique. Le boîtier assure le positionnement automatique du détecteur sensiblement contre le second site anatomique lorsque le stimulateur est disposé sensiblement contre le premier site anatomique. Le détecteur renferme une pluralité d'éléments de détection individuels. La réponse déclenchée par la stimulation au niveau du premier site anatomique est mesurée au moyen d'un ou de plusieurs des éléments de détection au niveau du second site anatomique.
PCT/US2002/004204 2001-02-15 2002-02-14 Dispositif et procede permettant de realiser des etudes de conduction nerveuse avec localisation des reponses declenchees WO2002065906A2 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2037802B1 (fr) * 2006-07-10 2012-05-30 Zanchinn Limited Procédé et dispositif de mesure de l'activité dans le système nerveux périphérique

Citations (3)

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US4817628A (en) * 1985-10-18 1989-04-04 David L. Zealear System and method for evaluating neurological function controlling muscular movements
US5611350A (en) * 1996-02-08 1997-03-18 John; Michael S. Method and apparatus for facilitating recovery of patients in deep coma
US5797854A (en) * 1995-08-01 1998-08-25 Hedgecock; James L. Method and apparatus for testing and measuring current perception threshold and motor nerve junction performance

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6132386A (en) * 1997-07-01 2000-10-17 Neurometrix, Inc. Methods for the assessment of neuromuscular function by F-wave latency

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4817628A (en) * 1985-10-18 1989-04-04 David L. Zealear System and method for evaluating neurological function controlling muscular movements
US5797854A (en) * 1995-08-01 1998-08-25 Hedgecock; James L. Method and apparatus for testing and measuring current perception threshold and motor nerve junction performance
US5611350A (en) * 1996-02-08 1997-03-18 John; Michael S. Method and apparatus for facilitating recovery of patients in deep coma

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Title
See also references of EP1367939A2 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2037802B1 (fr) * 2006-07-10 2012-05-30 Zanchinn Limited Procédé et dispositif de mesure de l'activité dans le système nerveux périphérique

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EP1367939A2 (fr) 2003-12-10
EP1367939A4 (fr) 2006-05-31
WO2002065906A9 (fr) 2002-12-12
WO2002065906A3 (fr) 2002-09-26

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