NEUROSTIMULATOR AND METHOD FOR REGULATING SAME

• US 20100222844A1
• Filed: 10/10/2007
• Published: 09/02/2010
• Est. Priority Date: 10/10/2007
• Status: Active Grant

• Current Assignee: Sorin CRM USA (MicroPort Scientific Corp.)
• Original Assignee: Sorin CRM USA (MicroPort Scientific Corp.)
• Inventors: Troosters, Michel, Mevel, Herve, Doguet, Pascal, Delbeke, Jean
• Granted Patent: US 9,248,274 B2
• Time in Patent Office: Days
• US Class Current: 607/59
• CPC Class Codes: A61N 1/0529 Electrodes for brain stimulation
• CPC Class Codes: A61N 1/0556 Cuff electrodes
• CPC Class Codes: A61N 1/3605 Implantable neurostimulators for stimulating central or peripheral nerve system
• CPC Class Codes: A61N 1/36139 with automatic adjustment

Abstract

The present invention relates to an electrode (30,30′) for implantation in contact with a neural tissue, said electrode extending along an axis, said neural tissue being capable of generating one or more action potentials, and said one or more action potentials propagating with a given speed in said neural tissue. The electrode comprises a carrier (31, 31′) of biocompatible electrically insulating material; stimulation electrode contacts (32a; 32′a; 32b; 32′b) deposited on a surface of said carrier (31, 31′) for applying an electrical stimulation to said neural tissue so as to generate, after a given latency time, a compound action potential when stimulated by said electrical stimulation; one or more sensing electrode contacts (33a; 33b; 33c; 33′a; 33′b; 33′c) deposited on said surface of said carrier and provided at a distance from said stimulation electrode contacts, said sensing electrode contacts being adapted to be connected to measuring means (23) having a given inactive period. The invention includes means to reduce the stimulation artifact. The invention also relates to an apparatus (20) and method for using various signals obtained from the stimulation probe itself and used to control the parameters of the current pulses applied to the electrodes.

Claims

1. An electrode for implantation in contact with a neural tissue, said electrode extending along an axis, said neural tissue being capable of generating one or more action potentials, said one or more action potentials propagating with a given speed in said neural tissue, said electrode comprising:

a carrier of biocompatible electrically insulating material;

stimulation electrode contacts deposited on a surface of said carrier for applying an electrical stimulation to said neural tissue so as to generate, after a given latency time, a compound action potential when stimulated by said electrical stimulation;

one or more sensing electrode contacts deposited on said surface of said carrier and provided at a distance from said stimulation electrode contacts said sensing electrode contacts being adapted to be connected to measuring means (23) having a given inactive period;

wherein said sensing electrode contacts are located at a predetermined distance Δ

e from the stimulation electrode contacts so that said compound action potential, generated by said stimulation electrode contacts reaches said sensing electrode contacts when said inactive period of said measuring means is already elapsed.

2. The electrode according to claim 1 wherein it comprises a cuff capable of fitting closely around a selected portion of an elongated nerve, said stimulation electrode contacts and sensing electrode contacts being deposited on a surface of said cuff in contact with said portion of the nerve.

3. The electrode according to claim 2 wherein said distance Δ

e is comprised between 2 mm and 20 mm.

4. The electrode according to claim 1 wherein said carrier comprises a lead capable of being inserted into a portion of a brain tissue, said stimulation electrode contacts and sensing electrode contacts being deposited on a surface of said lead in contact with said portion of the brain tissue.

5. The electrode according to claim 4 wherein said distance Δ

e is comprised between 1 mm and 15 mm.

6. The electrode according to claim 4 wherein said stimulation electrode contacts and sensing electrode contacts are arranged alternately along said lead.

7. The electrode according to claim 4 wherein it comprises a single stimulation electrode contact and a single sensing electrode contacts.

8. The electrode according to claim 4 wherein it comprises a single stimulation electrode contact and a pair of sensing electrode contacts arranged on opposite sides of said stimulation electrode contact.

9. The electrode according to any of claims 4 wherein it comprises a plurality of sensing electrode contacts arranged on a circumference of said lead.

10. The electrode according to claim 4 wherein said sensing electrode contacts form a tripole.

11. The electrode according to claim 4 wherein said sensing electrode contacts comprise a single electrode contact, a voltage reference being provided by an electrode contact located in a position remote from the electrode.

12. A nerve stimulation apparatus for inducing electrical stimulations to a neural tissue, the apparatus comprising:

a generator for generating electrical stimulations having specified amplitude and shape;

electrical connectors for connecting the apparatus to the electrode of any of claims 1 to 11; and

means for controlling the amplitude and shape of said electrical stimulations in such a way that the amplitude of the compound action potential measured by sensing electrode contacts reaches an expected value within desired time constraints.

13. The nerve stimulation apparatus of claim 12, wherein said regulation means comprises:

a microcontroller for controlling the amplitude and shape of said electrical stimulations;

an amplifier for amplifying and conditioning analog signals recorded by sensing electrode contacts;

an analog/digital signal converter for converting amplified analog signals into digital signals.

14. The nerve stimulation apparatus of claim 13, wherein said microcontroller comprises a programmed algorithm for automatically computing said specified amplitude and shape.

15. The nerve stimulation apparatus of claim 13, wherein said microcontroller comprises means for exchanging information with an external output device for displaying the compound action potential and an external input device, whereby an operator adapts said specified amplitude and shape depending on the displayed compound action potential.

16. The nerve stimulation apparatus of any of claim 13, wherein said amplifier is a variable-gain amplifier, wherein said gain is controlled by said microcontroller through input gain control line.

17. The nerve stimulation apparatus of claim 13 wherein said amplifier is provided with a short circuit next to its input ports, said short circuit being controlled by said microcontroller through the input short circuit control line.

18. The nerve stimulation apparatus of claim 13 wherein the power supply voltage of said amplifier is selected at a value which is higher than the maximum voltage of stimulation pulses produced by said generator.

19. The nerve stimulation apparatus of claims 13 further comprising a high-pass filter between said amplifier and said sensing electrode contacts and/or a low-pass filter between said amplifier and said A/D converter.

20. A method for regulating the intensity of electrical stimulations generated by a nerve stimulation apparatus comprising the steps of:

a. implanting the electrode claim 1 to in such a way as to be in contact with a portion of a neural tissue;

b. applying electrical stimulations on said portion by means of stimulation electrode contacts;

c. measuring the compound action potential generated by said stimulation electrode contacts through sensing electrode contacts;

d. adjusting the amplitude and shape of said electrical stimulations in order to obtain a desired compound action potential.

21. The method according to claim 20 wherein said step of applying electrical stimulations on said portion comprises applying a long-duration (t1), low-amplitude (A1) anodic phase and a subsequent relatively short-duration (t2), high-amplitude (A2) cathodic phase in order to activate the neural tissue at the very end of the charge balanced stimulation.

22. The method according to claim 21 wherein said anodic phase is applied with a progressive amplitude in order to avoid early tissue activation.

23. The method according to claim 21 further comprising the step of adjusting the cathodic to anodic phase ratio in order to minimize the stimulus artifact, the anodic charge recuperation phase duration being equal or slightly smaller than the cathodic stimulating phase duration.

24. The method according to claim 20 further comprising the step of reducing the amplitude and shape of said electrical stimulations when the measured compound action potential reaches a predetermined safety limit.

25. The method according to claim 24 further comprising the step of measuring at least one of the following parameter of said electrical stimulation:

local DC potential values;

stimulation voltage values;

tissue impedance values, in order to determine said safety limit for guaranteeing the safety of said portion of neural tissue.

26. The method according to claim 24 further comprising the step of measuring the voltage applied by said generator to said stimulation electrode contacts in order to determine said safety limit for preventing the corrosion of said stimulation electrode contacts.