A fully implantable and self contained device is disclosed composed of a flexible electrode array for surrounding damaged nerves and a signal generator for driving the electrode array with periodic electrical impulses of nanoampere magnitude to induce regeneration of the damaged nerves

Jhabvala, M. D.

English

NASA Technical Reports Server

United States Patent [I91 
Jhabvala 
300 K f l  
4,308,868 
Jan. 5, 1982 
[113 
1451 
[54] IMPLANTABLE ELECTRICAL DEVICE 
[75] Inventor: Murzban D. Jhabvala, Seabrook, Md. 
[73] Assignee: The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[21] Appl. No.: 153,246 
[22] Filed: May 27, 1980 
[51] Int. CI.3 ............................................... A61N 1/32 
[52] U.S. C1. .................................................... 128/421 
[58] Field of Search ........... 128/419 C, 419 E, 419 F, 
128/419 R, 421,422, 784, 785, 798, 799 
[561 References Cited 
U.S. PATENT DOCUMENTS 
3,654,933 4/1972 Hagfors ............................... 128/784 
3,774,618 11/1973 Avery ................................. 128/784 
3,893,462 7/1975 Manning ......................... 128/419 F 
4,105,017 8/1978 Ryaby et al. .................... 128/419 F 
Primary Examiner-William E. Kamm 
Attorney, Agent, or Firm-John 0. Tresansky; John R. 
Manning; Ronald F. Sandler 
[571 ABSTRACT 
A fully implantable and self-contained device is dis- 
closed composed of a flexible electrode array 10 for 
surrounding damaged nerves and a signal generator 12 
for driving the electrode array with periodic electrical 
impulses of nanoampere magnitude to induce regenera- 
tion of the damaged nerves. 
3,881,495 5/1975 Pannozzo et al. .................. 128/422 
8 Claims, 6 Drawing Figures 
https://ntrs.nasa.gov/search.jsp?R=19820021987 2020-03-21T17:13:55+00:00Z
U.S. Patent Jan. 5 ,  1982 Sheet 1 of 2 
FIG I/. 
20 
FIG 2. 
/I0 
Sheet 2 of 2 4,308,868 
4,308,868 
1 
IMPLANTABLE ELECTRICAL DEVICE 
ORIGIN O F  THE INVENTION 
The invention described herein was made by an em- 
ployee of the United States Government and may be 
manufactured and used by or for the Government for 
governmental purposes without the payment of any 
royalties thereon or therefor. 
DESCRIPTION 
1. TECHNICAL FIELD 
This invention relates generally to implantable thera- 
peutic devices and more particularly to an implantable 
device for inducing regeneration of severed nerves. 
2. BACKGROUND 
Medical science has progressed to the stage where 
devices implantable within the body have been devised 
for curing some of the ills of the body. Many such thera- 
peutic devices utilize electrical energy either to render 
the device operational or to act on the body to affect the 
cure, or both. Although, in general, these prior art de- 
vices have operated satisfactorily in many medical ap- 
plications, they have been found to be less than satisfac- 
tory in applications where space availability for im- 
plantables is limited or the use of a minutely sized im- 
plantable is required. Additionally, many of the existing 
implantable devices have energy needs which necessi- 
tate periodic re-energizing from an external energy 
source either through a percutaneous connector or by 
surgical removal of the device from the body. These 
energizing requirements are particularly undesirable in 
therapy necessitating prolonged implantation of the 
devices. In the developing area of regeneration of sev- 
ered, or damaged, nerves by the use of implantable 
electrically activated-devices to stimulate desired re- 
growth, the requirements of small size and low energy 
dissipation are especially acute. In addition, to avoid 
destruction of the nerves by overheating, the electrical 
energy applied by such devices must be under 200 na- 
noamperes in a pulsed mode. 
STATEMENT O F  INVENTION 
Accordingly, one object of the invention is to pro- 
vide a new and improved fully implantable electrically 
energized therapeutic device of small size and energy 
dissipation. 
Another object of this invention is to provide an 
electrically energized therapeutic device capable of 
long term implantation. 
A further object of the present invention is to provide 
a fully implantable therapeutic device which is self 
energized and capable of generating electrical impulses 
suitable for stimulating severed nerve regeneration. 
A still further object of this invention is to provide a 
compact, low power dissipating and self energized 
source of electrical impulses of about 10 nanoamperes. 
These and other objects are attained by a fully im- 
plantable self energized and small-sized electrical de- 
vice formed of an array of electrodes for surrounding a 
damaged nerve and a signal generator for applying 
periodic low current impulses to the electrodes in a 
manner to generate electrical fields which induce regen- 
eration of damaged nerves. 
BRIEF DESCRIPTION O F  DRAWINGS 
In the drawings the references designate like parts 
FIG. 1 is a diagrammatic view of the overall implant- 
FIG. 2 is a view, partially in perspective, of the appli- 
FIG. 3 is a schematic view of the signal generator of 
FIG. 4 shows the waveforms at various points of the 
throughout the several views, and wherein: 
able device; 
cation of the device; 
5 
10 the device; and 
signal generator of FIG. 3. 
DETAILED DESCRIPTION OF THE 
INVENTION 
The implantable device of this invention is shown in 
FIG. 1 as being composed of an electrode array 10 and 
a signal generator 12 interconnected by wires 14 and 16. 
The signal generator provides the driving energy for 
The electrode array is formed of a sheet 18 of flexible 
mesh material which is compatible with living tissue, 
such as Silastic. Three equal lengths of flexible wire 20 
are woven within the mesh material in a parallel spaced 
25 relationship to act as electrodes. The wires are prefera- 
bly made of bio-compatible platinum. The outer ones of 
electrodes 20 are conjointly connected by wire 16 to 
one output terminal of generator 12 while the center 
electrode is connected by wire 14 to the other output 
FIG. 2 illustrates the application of the invention to 
the therapeutic purpose of inducing regeneration of 
severed nerves of an animal. Severed nerves do not 
always rejoin, and when they do, they rejoin somewhat 
35 haphazardly and not directly at their endings. Because 
of the ionic action of nerves, it is believed that proper 
regeneration of severed nerves can be stimulated under 
the influence of electric fields which will serve to orient 
the severed nerves to regenerate. Such electric fields 
40 can be generated by closely wrapping electrode array 
10 around an organ containing the damaged nerves 22, 
such for example as those present in the spinal chord of 
an animal, in a manner that the electrodes 20 will be 
substantially perpendicular to the direction of desired 
45 regeneration. In the cited example the peripheral di- 
mensions of the array 10 may be about 1 inch square. To 
equally stimulate both endings of the severed nerve, the 
center electrode is preferably positioned at the break 
and each of the end electrodes are located about oppo- 
50 site ends of the severed nerve. It will be apparent that 
upon the application of an electrical signal from signal 
generator 12 to the electrode array 10, as connected, a 
potential difference of the proper polarity will be devel- 
oped between the center electrode and each of the outer 
55 electrodes which will develop electric fields for orient- 
ing regrowth of the severed nerve endings toward one 
another. 
Medical research indicates that nerve tissue will burn 
and can be destroyed by being subjected to the influ- 
60 ence of certain levels of electrical energy. Thus, it is 
considered essential that the electrical signal applied to 
the electrode array be discontinuous and of a low am- 
perage level. Signal generator 12 provides such a signal 
to electrode array 10. 
As shown in FIG. 3, signal generator 12 consists of a 
plurality of inverters 24, 26, 28, 30 and 32 which are 
energized by a common direct current source 34. 
CMOS technology is employed in the inverters to re- 
15 
20 the electrode array. 
30 terminal. 
65 
4,308,868 
3 4 
duce the energy needs of the circuit and, therefore, 
direct current source 34 may be a pair of watch-type 
disc shaped batteries of 1.35 volts each. Inverters 24 and 
26 are interconnected to operate as a conventional asta- 
ble multivibrator 27. Oscillation is initiated by a seed 5 
voltage, or noise: and is sustained by a feedback loop 36. 
A phase shifting capacitor 38 is included in the loop, 
which in conjunction with a pair of serially connected 
Accordingly, the invention having been disclosed in 
its best embodiment and mode of operation, that which 
is desired to be claimed by Letters Patent is: 
1. An implantable therapeutic device comprising: 
a flexible electrode array for surrounding a nerve in 
its damaged area; 
circuit means for developing a continuous series of 
square wave pulses of electrical energy at a prede- 
resistors 40, 42 sets the frequency of operation of the 
multivibrator stage. A diode 44 is shunted across resis- 
tor 40 to regulate the duty cycle of oscillation. With the 
indicated magnitude of parameters, a square wave out- 
put signal is provided by the multivibrator, as shown in 
FIG. 4A, with an amplitude of about 2.7 volts at a fre- 
quency of 10 Hz and a fifty percent duty cycle. 
The square wave output of the multivibrator stage is 
applied to a conventional pulse shaping stage 46 com- 
posed of inverters 28 and 30. This stage reshapes the 
multivibrator output by stretching each square wave. A 
resistor 48 and a capacitor 50 are included to operate as 
a timing circuit for determining the duration of the gap 
between each stretched square wave, as shown in FIG. 
4B. With the magnitude of parameters indicated, the 
output signal consists of 10 Hz pulses of about 2.7 volts 
amplitude with an intervening gap of 0.1 millisecond. 
The output signal of the pulse shaper 46 is fed to an 
inverter stage 32 wherein the polarity of the output 
signal is inverted to provide a 0.1 millisecond pulse of 
about 2.7 volts at a frequency of 10 Hz. Because nerves 
exhibit practically zero electrical resistance, it is essen- 
tial that the developed short duration pulse not be di- 
rectly applied to electrode array 10 but be applied seri- 
ally through a large current limiting resistor 54. With 
the magnitude of resistor 54 as shown in FIG. 3, the 
maximum level of the electrical energy to which a 
nerve will be subjected is an impulse of about 10 na- 
noamperes at a potential of about 2 volts. This amper- 
age is well below the level of 200 nanoamperes of con- 
tinuous current which is believed to be the maximum 
safe amount of electrical energy to which a nerve may 
be exposed. 
A pulse generator circuit according to FIG. 3 was 
built on a hybrid ceramic 0.4" square and along with the 
batteries were encapsulated and hermetically sealed in a 
package about the size of a quarter coin. This generator 
can be operationally coupled to electrode array 10 by 
wires 14 and 16. Thus, it should be readily apparent that 
a simple, compact and low power dissipation device 
suitable for long duration tool implantation has been 
disclosed. 
termined frequency; 
circuit means for stretching each of said square wave 
pulses. 
circuit means for reversing the polarity of said 
stretched square wave pulses to provide short du- 
ration impulses of electrical energy; 
10 
15 means for energizing all of said circuit means; and 
impedance means for applying a series of said short 
duration impulses of electrical energy in the nano- 
second range to said array to regenerate the dam- 
aged area of said nerve. 
2. The device according to claim 1 wherein said elec- 
a piece of mesh material, and 
a plurality of parallel spaced electrodes woven into 
3. The device according to claim 2 wherein the center 
one of said electrodes is positioned directly at the area 
of damage of the nerve and the remaining ones of said 
electrodes are positioned on opposite sides of said cen- 
ter one about the nerve. 
4. The device according to claim 3 wherein said im- 
pedance means applies said impulses to said center one 
of said electrodes thereby establishing a potential differ- 
ence between it and said remaining ones of said elec- 
trodes. 
5. The device according to claim 4 wherein said ap- 
plied impulses are less than 200 nanoamperes and of 
about 0.1 millisecond duration. 
6. The device of claim 2 wherein the electrodes of 
said array are transversely disposed around said nerve 
40 with an intermediate one of said parallel spaced elec- 
trodes positioned directly at said damaged area and 
adjacent ones of said electrodes are positioned on oppo- 
site sides of said intermediate one. 
7. The device of claims 1 or 6 wherein said impedance 
45 means discontinuously applies electrical energy to said 
array. 
8. The device according to claim 1 wherein said im- 
pulses provided by said impedance means are about 10 
nanoamperes. 
20 
trode array includes: 
said mesh material. 
25 
30 
35 
e * * * *  50 
55 
60 
65 
UNITED STATES PATENT AND TRADEMARK OFFICE 
Certificate 
Patent No. 4,308,868 Patented January 5, 1982 
MURZBAN D. JHABVALA 
Application having been made by Murzban D. Jhabvala, the inventor named 
in the patent above identified, and The United States of America as represented 
by the Administrator of the National Aeronatics and Space Administration, the 
assignee, for the issuance of a certificate under the provisions of Title 35, Section 
256, of the United States Code, adding the name of Donald D. Rigamonti as a 
joint inventor, and a showing and proof of facts satisfying the requirements of 
the said section having been submitted, it is this 12th day of July 1983, certified 
that the name of the said Donald D. Rigamonti is hereby added to the said pa- 
tent as a joint inventor with the said Murzban D. Jhabvala. 
Fred W. Sherling, 
Associate Solicitor 


Implantable electrical device

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