Non-invasive, peripheral nerve mapping device and method of use

• US 5,560,372 A
• Filed: 02/02/1994
• Issued: 10/01/1996
• Est. Priority Date: 02/02/1994
• Status: Expired due to Term

• Current Assignee: Nervonix, Inc.
• Original Assignee: Philip C. Cory
• Inventors: Cory, Philip C.
• Primary Examiner(s): Sykes, Angela D.
• Application Number:
  US08/190,394
• Time in Patent Office: 972 Days
• Field of Search: 128/639, 128/644, 128/734, 128/741, 128/774
• US Class Current: 600/554
• CPC Class Codes: A61B 2562/0215 Silver or silver chloride containing
• CPC Class Codes: A61B 5/05 Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves impedance plethysmography A61B5/0295; measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24
• CPC Class Codes: A61B 5/4041 Evaluating nerves condition
• CPC Class Codes: A61B 5/4893 Nerves

Abstract

A device for non-invasively locating the presence of peripheral nerves. The peripheral nerve mapping device has a sampling electrode comprising an array of a plurality of sub-electrodes, a reference electrode, a square wave constant current source, and a multiplexer serially multiplexed to the array of the sub-electrodes. The voltage differential between each of the sub-electrodes and the reference electrode is measured as the current is serially distributed to the sub-electrodes and displayed on an array of light emitting diodes. The voltage differential indicates the presence of peripheral nerves and may be used to identify sites of nerve trauma or transection.

Claims

1. A non-invasive, peripheral nerve mapping device comprising:

means for sampling a plurality of electrical conductance sites, said sampling means comprising a sampling electrode having an array of a plurality of sub-electrodes, each sub-electrode comprising an absorbent tip having a surface area of approximately 3-20 square millimeters, each sub-electrode being mounted on movable pistons;

guide tube means mounted to said device, said pistons being movable through said guide tube means, each of said sampling electrodes being in electrical contact with each of said guide tube means;

reference electrode means comprising a standard silver-silver chloride electrocardiographic electrode;

a square wave constant current source with an adjustable frequency output and an adjustable amplitude output;

a multiplexer having an output, said multiplexer output being serially multiplexed to said array of plurality of sub-electrodes;

an array of light emitting diodes to display conductivity measurements;

wherein a current from said constant current source is selectively conveyed by said multiplexer to said sub-electrodes across the skin of a patient, with a corresponding voltage difference between each of the sub-electrodes and the reference electrode being measured as the current is conveyed to said sub-electrodes and displayed by said array of light emitting diodes, the displayed voltage difference being indicative of a local electrical conductance of said intact skin.

2. The device according to claim 1, wherein the current is adjustable from 0.0 to 1.0 milliamps, and the frequency is adjustable from 0 to 1000 hertz.

3. The non-invasive, peripheral nerve mapping device according to claim 1, wherein the array of electrodes is a linear array of eight electrodes.

4. A method of non-invasively locating peripheral nerves in a patient'"'"'s body, comprising the steps of:

a) providing a nerve mapping device having

i) a plurality of sub-electrodes;

ii) a reference electrode; and

iii) a source of constant current that can be directed to each of said sub-electrodes;

b) placing said sub-electrodes and said reference electrode in contact with a patient'"'"'s skin;

c) supplying said constant current to each of said sub-electrodes;

d) measuring a respective local voltage difference between each of said sub-electrodes and said reference electrode across said skin of said patient, said local measured voltage difference corresponding to a local electrical conductance of said skin of said patient; and

e) comparing said respective local measured voltage differences for said sub-electrodes; and

thereby identifying a presence of a peripheral nerve based on a decrease in measured local voltage for one of said sub-electrodes relative to the measured local voltage differences for other sub-electrodes.

5. The method of claim 4 comprising the step of multiplexing said constant current serially to said sub-electrodes.

6. The method of claim 4, wherein said constant current is adjustable in frequency and amplitude.

7. The method of claim 4 further comprising the step indicating which said sub-electrode represents said decrease in measured voltage.

8. The method of claim 4 wherein said placing step further comprises placing each sub-electrode and said reference electrode in opposing relationship on said patient'"'"'s skin.

9. A non-invasive nerve mapping device, comprising:

a) a housing;

b) a plurality of sub-electrodes, at least a portion of each sub-electrode being arranged in said housing;

c) a square wave constant current source;

d) a multiplexer in said housing, said multiplexer providing said constant current serially to each of said sub-electrodes;

e) a reference electrode;

f) a voltage measuring device for measuring a respective voltage difference between each of said sub-electrodes and said reference electrode and between said sub-electrodes when said constant current is applied to each said sub-electrode, the voltage difference indicating electrical conductance of said intact skin; and

g) an indicator for each sub-electrode, each indicator being responsive to a decrease in voltage as measured by said voltage measuring device, whereby a peripheral nerve presence is determined adjacent a sub-electrode associated with said decrease.

10. The device of claim 9 wherein each said indicator is a light emitting diode.

11. The device of claim 9 wherein said reference electrode is one of a conductive carbon impregnated silastic pad with an insulated metal foil sheet laminated thereto and a silver-silver chloride electrode.

12. The device of claim 9 further comprising adjustable frequency and amplitude circuits for said constant current source.

13. The device of claim 9 wherein said sub-electrodes further comprises a linear array of eight electrodes.