WO1997037721A1 - Technique pour ajuster le site d'excitation d'un tissu excitable electriquement - Google Patents

Technique pour ajuster le site d'excitation d'un tissu excitable electriquement Download PDF

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Publication number
WO1997037721A1
WO1997037721A1 PCT/US1997/004908 US9704908W WO9737721A1 WO 1997037721 A1 WO1997037721 A1 WO 1997037721A1 US 9704908 W US9704908 W US 9704908W WO 9737721 A1 WO9737721 A1 WO 9737721A1
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WO
WIPO (PCT)
Prior art keywords
pulse
locus
pulses
timing relationship
tissue
Prior art date
Application number
PCT/US1997/004908
Other languages
English (en)
Inventor
Gary William King
Michael David Baudino
Original Assignee
Medtronic, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Medtronic, Inc. filed Critical Medtronic, Inc.
Priority to AU24239/97A priority Critical patent/AU2423997A/en
Publication of WO1997037721A1 publication Critical patent/WO1997037721A1/fr

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00—Electrotherapy; Circuits therefor
    • A61N1/18—Applying electric currents by contact electrodes
    • A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
    • A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
    • A61N1/3605—Implantable neurostimulators for stimulating central or peripheral nerve system
    • A61N1/36128—Control systems
    • A61N1/36146—Control systems specified by the stimulation parameters
    • A61N1/3615—Intensity
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00—Electrotherapy; Circuits therefor
    • A61N1/18—Applying electric currents by contact electrodes
    • A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
    • A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
    • A61N1/3605—Implantable neurostimulators for stimulating central or peripheral nerve system
    • A61N1/3606—Implantable neurostimulators for stimulating central or peripheral nerve system adapted for a particular treatment
    • A61N1/36071—Pain
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00—Electrotherapy; Circuits therefor
    • A61N1/18—Applying electric currents by contact electrodes
    • A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
    • A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
    • A61N1/3605—Implantable neurostimulators for stimulating central or peripheral nerve system
    • A61N1/36128—Control systems
    • A61N1/36146—Control systems specified by the stimulation parameters
    • A61N1/36167—Timing, e.g. stimulation onset
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00—Electrotherapy; Circuits therefor
    • A61N1/18—Applying electric currents by contact electrodes
    • A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
    • A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
    • A61N1/36014—External stimulators, e.g. with patch electrodes
    • A61N1/36017—External stimulators, e.g. with patch electrodes with leads or electrodes penetrating the skin

Definitions

  • This invention relates to means of stimulating electrically excitable tissue, and more particularly relates to means for adjusting the locus at which action potentials are induced in such tissue.
  • first and second electrodes are implanted adjacent the tissue to be stimulated.
  • a first electrical pulse is applied to the first electrode and a second electrical pulse is applied to the second electrode.
  • the first and second pulses have a timing relationship such that the combined potentials induced in the locus by the first and second pulses create action potentials in the locus.
  • Means are provided for adjusting the timing relationship so that the locus is altered.
  • the degree of surgical precision required for the implanting ofthe electrodes is reduced, because the locus at which the nerve fibers are stimulated can be adjusted by merely changing the timing relationship of the pulses applied to the electrodes after the surgical procedure is completed.
  • the amplitudes and pulse widths ofthe first and second pulses can be altered, as well as the timing relationship, in order to further alter the locus of the tissue at which action potentials are induced.
  • Figure 1 is a diagrammatic view of a patient in which a preferred form of apparatus for SCS made in accordance with the invention has been implanted
  • Figure 2 is a cross-sectional view of an exemplary spinal column showing a typical position at which electrodes made in accordance with the preferred practice of the invention have been implanted in the epidural space;
  • Figure 3 is a cross-sectional view like Figure 2 showing locus of potential changes induced in the spinal cord from a pulse applied to a first one of two electrodes;
  • Figure 4 is a view like Figure 3 showing the locus of potential changes induced in the spinal cord from the application of a pulse to the second ofthe electrodes;
  • Figure 5 is a view like Figure 4 showing the combined loci in the spinal cord at which potentials are induced from pulses applied to the first and second electrodes;
  • Figure 6 is a view like Figure 5 showing the alteration of the loci due to increase in the amplitude ofthe pulse applied to the first electrode and a decrease in amplitude ofthe pulse applied to the second electrode;
  • Figure 7 is a view like Figure 6 showing the alteration ofthe loci due to an increase in amplitude of the pulse applied to the second electrode and a decrease in amplitude ofthe pulse applied to the first electrode;
  • Figure 8 is a timing diagram showing pulses applied to the first and second electrodes illustrated in Figure 2 in relationship to the potentials induced in tissue adjacent the electrodes;
  • Figures 9 and 10 are timing diagrams illustrating alternative forms of pulses applied to the electrodes illustrated in Figure 2;
  • Figure 1 1 is a timing diagram illustrating a preferred form of pulses applied to the electrodes shown in Figure 2. DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • a single electrical pulse PI can cause depolarization near a cathode in electrically excitable tissue which includes neural tissue and muscle tissue.
  • Neural tissue includes peripheral nerves, the spinal cord surface, deep spinal cord tissue, deep brain tissue, and brain surface tissue.
  • Muscle tissue includes skeletal (red) muscle, smooth (white) muscle, and cardiac muscle.
  • a locus includes a set of points in three-dimensional space and refers to a volume of cells or parts of cells. Due to the electrical characteristics of both the three-dimensional volume conductor and the membrane properties, the potentials outside and inside a neuron respond to the depolarization, usually with exponential-type increases and then attenuation over time.
  • the time constant for an isolated neuron membrane typically is 5-15 milliseconds (Nerve, Muscle and Synapse by Bernard Katz, circa 1972). For myelinated axons or muscle cells, it may be considerably shorter.
  • the local depolarization from a single pulse PI results in a transmembrane potential PT1 between times TI and T3.
  • the peak of potential PT1 is below the transmembrane potential threshold TPT.
  • the pulse fails to produce an action potential in that cell.
  • Action potential is an all-or-none, nonlinear phenomenon, caused by opening of sodium gates, inrush of sodium of ions, and a delayed opening of potassium gates and a restoration ofthe membrane potential.
  • a certain amount of charge must be passed at the electrodes (amplitude [Volts] / resistance [Ohms] x pulse width
  • Electrode Basic neurophysiological principles, called “electrotonus”, show that in any volume of electrically excitable tissue in which two or more pulses, each of which alone is insufficient to bring the cells to threshold, arrive closely together in time, at least part of their effect is additive, i.e., the memory ofthe first pulse is still present when the second pulse arrives. If the sum ofthe potentials (distorted by resistive and capacitive properties of the surroundings and the cell membranes) can get some cells depolarized to threshold, then an action potential will start in those cells.
  • FIG. 8 is a schematic view of a patient 10 having an implant of a neurological stimulation system employing a preferred fo ⁇ n ofthe present invention to stimulate spinal cord 12 ofthe patient.
  • the preferred system employs an implantable pulse generator 14 to produce a number of independent stimulation pulses which are sent to spinal cord 12 by insulated leads 16 and 18 coupled to the spinal cord by electrodes 16A and 18A ( Figure 2). Electrodes 16A and 18A also can be attached to separate conductors included within a single lead.
  • Implantable pulse generator 14 preferably is a modified ITREL II implantable pulse generator available from Medtronic, Inc. with provisions for multiple pulses occurring either simultaneously or with one pulse shifted in time with respect to the other, and having independently varying amplitudes and pulse widths.
  • This preferred system employs a programmer 20 which is coupled via a conductor 22 to a radio frequency antenna 24. This system permits attending medical personnel to select the various pulse output options after implant using radio frequency communications. While the preferred system employs fully implanted elements, systems employing partially implanted generators and radio-frequency coupling may also be used in the practice ofthe present invention (e.g., similar to products sold by Medtronic, Inc. under the trademarks X-trel and Mattrix).
  • Figure 2 is a cross-sectional view of spine 12 showing implantation of the distal end of insulated leads 16 and 18 which terminate in electrodes 16A and 18A within epidural space 26.
  • the electrodes may be conventional percutaneous electrodes, such as PISCESD model 3487A sold by Medtronic, Inc. Also shown is the subdural space 28 filled with cerebrospinal fluid (cfs), bony vertebral body 30, vertebral arch 31, and dura mater 32.
  • the spine also includes gray matter 34 and dorsal horns 36 and 37 and white matter, for example, dorsal columns 46 and dorsal lateral columns 47.
  • pulse P 1 is applied to electrode 18A ( Figure 2) and pulse P2 is applied electrode 16A ( Figure 2).
  • Pulses PI and P2 have a timing relationship. For example, the end of pulse PI at time T2 and the start of pulse P2 at time T3 are displaced by a predetermined time period less than 500 microseconds, and preferably less than 50 microseconds.
  • Amplitude Al of PI is adjustable independently from amplitude A2 of pulse P2.
  • the pulse widths of pulses PI and P2 also are independently adjustable. Widening the pulse widths of each pulse (i.e., PI and P2) can also expand the loci of depolarizations, just like increasing amplitude, either voltage or current amplitude.
  • the pulses P 1 and P2 also could have other timing relationships in order to accomplish the goals ofthe present invention.
  • pulses P3 and P4, having different rise times could be used.
  • P3 has a rise time from TI to T8 and P4 has a rise time from TI to T9.
  • pulses P5 and P6, having different fall times could be used.
  • P5 has a fall time from T10 to TI 1
  • P6 has a fall time from T10 to T12.
  • the weighted average WA3 of pulse P3 ( Figure 9) is displaced from the weighted average WA4 of pulse P4 by a predetermined time period of less than 500 microseconds and preferably less than 50 microseconds.
  • the peak PK3 of pulse P3 is displaced from the peak PK4 of pulse P4 by a predetermined time period of less than 500 microseconds and preferably less than 50 microseconds. Objectives ofthe invention also can be achieved using combinations of the foregoing timing relationships.
  • line Ll represents the edge of a three-dimensional locus L1A in which pulse PI applied to electrode 18A induces a potential PT1 between times TI and T3 that is less than the transmembrane potential threshold TPT for cells of interest in that locus.
  • line L2 represents the edge of another three-dimensional locus L2A in which the application of pulse P2 ( Figure 8) to electrode 16A induces a depolarizing potential less than the transmembrane potential threshold TPT for cells of interest in that locus.
  • Figure 5 illustrates a locus L3A representing the intersection of loci L1A and L2A in which the combined potentials induced in locus L3A from pulses PI and P2 create an action potential in cells of interest in locus L3A as illustrated by potential PT3 in Figure 8.
  • the potential induced in locus Ll A outside locus L3A is illustrated by potential PT1 ( Figure 8). Since PT1 is lower than the transmembrane potential threshold TPT, there is no action potential created in locus Ll A outside L3A.
  • potential PT2 Figure 8).
  • line L4 represents the edge of another three-dimensional locus L4A resulting from the application of a pulse PI to electrode 18A having an amplitude greater than amplitude Al ( Figure 8), and line L5 represents the edge of another three-dimensional locus L5A resulting from the application of a pulse P2 to electrode 16A having an amplitude less than amplitude A2.
  • the intersection of loci L4A and L5A creates a locus L6A in which action potentials are induced. Locus L6A is moved mostly to the right relative to locus L3A shown in Figure 5. Action potentials are not induced outside locus L6A.
  • line L8 represents the edge of another three-dimensional locus L8A resulting from the application of a pulse P2 to electrode 16A having an amplitude greater than amplitude A2 ( Figure 8).
  • line L7 represents the edge of another three-dimensional locus L7A resulting from the application of a pulse PI to electrode 18 A having an amplitude less than amplitude Al .
  • the intersection of loci L7A and L8A creates a locus L9A in which action potentials are induced. It will be noted that the locus L9A is moved to the left compared with locus L3A shown in Figure 5. Action potentials are not induced outside locus L9A.
  • the ability to move the locus in which action potentials are induced is an important feature. In many therapies, it is important to prevent action potentials being induced in gray matter 34 or dorsal horns 36 and 37, dorsal roots 38 and 40, dorsal lateral columns 47 or peripheral nerves 42 and 44 in order to minimize the possibility of causing pain, motor effects, or uncomfortable paresthesia.
  • the locus in which action potentials are induced e.g., L3A, L6A or L9A
  • the ability to move the locus in which action potentials are induced drastically reduces the accuracy necessary for surgically implanting electrodes 16A and 18A, and may eliminate the need for surgical lead revisions.
  • Figure 1 1 illustrates a preferred timing relationship between pulse P7 applied to electrode 18A and pulse P8 applied to electrode 16A.
  • pulse generators use a biphasic pulse to insure no net direct current flows into the tissue.
  • pulse P8 has a net charge delivered of A2*(T4-T3).
  • This injected charge is balanced by the negative pulse PI 0, whose charge is A3*(T5-T4), where A3 «A2 and (T5-T4)»(T4-T3). Similar principles apply even if the first and second pulses are not of constant amplitude.
  • pulse P7 may be generated with a trailing negative pulse P9 from time T4 to time T5, so that the output on electrode 18A is substantially at neutral or 0 potential until the termination of pulse P8 at time T4. Having this delay in charge balancing prevents the loss of potential in adjacent tissue that otherwise would occur if pulse P9 immediately followed pulse P7 and overlapped with pulse P8, thus offsetting the benefit of pulse P8.
  • both negative pulses P9 and P10 begin in order to maintain the charge balance in tissue adjacent to the respective electrodes 18A and 16A.

Abstract

Une première et une deuxième impulsion électrique sont transmises à un ou plusieurs fils implantés (16, 18) qui incluent, respectivement, une première et la deuxième électrode (16A, 18A). Le rapport de temporisation entre la première et la deuxième électrode est choisi de manière à permettre aux potentiels combinés d'induire des potentiels d'action dans un certain site du tissu électriquement excitable (12). Des moyens sont fournis pour ajuster le rapport de temporisation et les paramètres des impulsions afin de modifier le site d'excitation.
PCT/US1997/004908 1996-04-04 1997-03-28 Technique pour ajuster le site d'excitation d'un tissu excitable electriquement WO1997037721A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU24239/97A AU2423997A (en) 1996-04-04 1997-03-28 Techniques for adjusting the locus of excitation of electrically excitable tissue

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US62757896A 1996-04-04 1996-04-04
US08/627,578 1996-04-04

Publications (1)

Publication Number Publication Date
WO1997037721A1 true WO1997037721A1 (fr) 1997-10-16

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7930037B2 (en) 2003-09-30 2011-04-19 Medtronic, Inc. Field steerable electrical stimulation paddle, lead system, and medical device incorporating the same
WO2020128748A1 (fr) * 2018-12-20 2020-06-25 Galvani Bioelectronics Limited Système de stimulation de nerf

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4813418A (en) * 1987-02-02 1989-03-21 Staodynamics, Inc. Nerve fiber stimulation using symmetrical biphasic waveform applied through plural equally active electrodes
US5121754A (en) * 1990-08-21 1992-06-16 Medtronic, Inc. Lateral displacement percutaneously inserted epidural lead
WO1995019804A1 (fr) * 1994-01-24 1995-07-27 Medtronic, Inc. Appareil multi-canal pour la stimulation epidurale du cordon medulaire

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4813418A (en) * 1987-02-02 1989-03-21 Staodynamics, Inc. Nerve fiber stimulation using symmetrical biphasic waveform applied through plural equally active electrodes
US5121754A (en) * 1990-08-21 1992-06-16 Medtronic, Inc. Lateral displacement percutaneously inserted epidural lead
WO1995019804A1 (fr) * 1994-01-24 1995-07-27 Medtronic, Inc. Appareil multi-canal pour la stimulation epidurale du cordon medulaire

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7930037B2 (en) 2003-09-30 2011-04-19 Medtronic, Inc. Field steerable electrical stimulation paddle, lead system, and medical device incorporating the same
US9867980B2 (en) 2003-09-30 2018-01-16 Medtronic, Inc. Field steerable electrical stimulation paddle, lead system, and medical device incorporating the same
WO2020128748A1 (fr) * 2018-12-20 2020-06-25 Galvani Bioelectronics Limited Système de stimulation de nerf

Also Published As

Publication number Publication date
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