Lead assembly with selectable electrode connection

The multi-conductor lead assembly comprises a first lead, a second lead and a connector assembly for connecting the leads together. The first lead includes a lead body having a distal end portion with a plurality of electrodes thereon, a proximal end portion with a plurality of sleeve electrodes thereon and a plurality of insulated wire conductors within the lead body and electrically connecting the electrodes on the distal end portion with the sleeve electrodes on the proximal end portion. The second lead includes a lead body with a proximal end, a proximal end portion, a distal end and a distal end portion, and one wire conductor therein. The connector assembly includes a body, the distal end portion of the second lead being received in the body, a connector clip adapted to make electrical contact with a selected one of the plurality of sleeve electrodes on the first lead, an electrical connection between the wire conductor in the second lead and the connector clip, and a closure sleeve for insulating the connection between the connector clip and a selected sleeve electrode.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a multi-conductor lead assembly comprising 
a first lead, a second lead and a connector assembly for connecting the 
proximal end portion of the first lead to the distal end portion of the 
second lead. More specifically, the invention relates to the connector 
assembly which provides a simple and effective structure for connecting a 
conductor in the second lead to one of several sleeve electrodes on the 
proximal end of the first lead in a sealed manner whereby the connector 
assembly can be inserted in body tissue after the distal end of the first 
lead with ring electrodes thereon has been implanted in body tissue, 
electrical tests first have been made, by means of electrical connections 
to the sleeve electrodes on the proximal end of the first sleeve, on the 
sensitivity of the implanted ring electrodes and a connection is made from 
a selected ring electrode on the distal end of the first lead to the 
conductor in the second lead. 
2. Description of the Prior Art 
Heretofore, it has been desirable, in the field of multi-electrode leads 
which are inserted into the epidural space within the spine and adjacent 
the spinal cord, to be able to determine which of a number, such as, for 
example, four, electrodes implanted in the spine are in good conductive 
contact with the spinal cord. In this respect, it is desirable to be able 
to test and determine which of the distal electrodes has the best 
conductive contact with the spinal cord. 
One technique which has been proposed for achieving this result is to 
provide a cathode electrode assembly having four equally spaced in line 
electrodes along the exterior of a sheath at the distal end of the 
catheter which are connected to proximal terminals at the proximal end by 
individually insulated strands of steel wire conductor. 
A wire is connected to and extends from each of the proximal terminals to 
an external terminal each of which is adapted to extend out of body tissue 
for cutaneous testing during a trial period of stimulation. The wires are 
cut adjacent the proximal terminals and removed prior to permanent 
implantation of the multi-conductor lead assembly and before the proximal 
terminals at the proximal end of the catheter are connected to an 
implanted stimulator. 
Such an assembly is disclosed in the Borkan et al U.S. Pat. No. 4,379,462. 
As will be described in greater detail hereinafter, the multi-conductor 
lead assembly of the present invention, instead of having external 
terminals which are cut away from a lead, includes two leads, a first lead 
which has distal electrodes adapted to be implanted within a spine, a 
second lead with having a wire conductor therein and a proximal terminal 
assembly including a terminal pin adapted to be inserted into a neural 
stimulator, and a connector assembly at the distal end of the second lead 
into which the proximal end of the first lead is adapted to be inserted 
after testing is performed, such as with alligator clips connected to 
sleeve electrodes on the proximal end portion of the first lead when it is 
withdrawn from the tissue for testing purposes. After the testing, the 
proximal end of the first lead is inserted into the connector assembly and 
a clip connector at the distal end of an insulated wire conductor 
connected to the wire conductor in the second lead is connected to a 
selected one of the sleeve electrodes on the proximal end of the first 
lead. Then the connector assembly is sealed and implanted in body tissue 
and the proximal end of the wire conductor in the second lead is connected 
to an implanted or external neural stimulator. 
SUMMARY OF THE INVENTION 
According to the present invention there is provided a multi-conductor lead 
assembly comprising: 
a first lead including a lead body having a distal end portion with a 
plurality of electrodes thereon, a proximal end portion with a plurality 
of sleeve electrodes thereon and a plurality of insulated wire conductors 
within the lead body and electrically connecting the electrodes on said 
distal end portion with the sleeve electrodes on the proximal end portion; 
a second lead including a lead body having a proximal end, a proximal end 
portion, a distal end and a distal end portion, and an insulated wire 
conductor therein having a proximal end and a distal end; 
a terminal assembly including a terminal pin connected to the proximal end 
of the wire conductor in the second lead; and 
a connector assembly including a body, the distal end portion of the second 
lead being received in the body, a flexible insulated wire conductor 
having a proximal end in the body and electrically connected to the distal 
end of the wire conductor in the second lead and a distal end, a connector 
clip connected to the distal end of the flexible insulated wire conductor 
and adapted to make electrical contact with a selected one of the 
plurality of sleeve electrodes on the first lead, and means for insulating 
the connection between the connector clip and a selected one of the sleeve 
electrodes.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In FIG. 1 there is illustrated a multi-conductor lead assembly 10 
constructed according to the teachings of the present invention. The 
assembly 10 includes a first distal lead 12, a second proximal lead 14, 
and a connector assembly 16 connecting the two leads 12 and 14 together. 
FIG. 1 shows the connector assembly 16 of the present invention in its 
assembled sealed state mounted within body tissue. 
The first lead 12 includes a lead body 17 having a distal end portion 18 
having four ring electrodes 21-24 (or three ring electrodes 21-23 and one 
tip electrode 24) (FIG. 1) thereon which are positioned within the 
epidural space of the spine so that at least one of the ring electrodes 
21-24 is in a position to supply electrical current signals to nerve 
tissue for the purpose of interfering with, and blocking, pain signals. 
The electrical current path can be between one ring electrode 21-24 and an 
anode connected to the body remotely from the position of the ring 
electrodes 21-24 or between any two of the ring electrodes 21 and 24 when 
two spring connector clips (92 in FIG. 2) are provided. 
A proximal end portion 30 (FIG. 2) of the first lead 12 hidden from view in 
FIG. 1 has four sleeve electrodes 31-34 (FIG. 2) which are received in the 
connector assembly 16. The connector assembly 16 is mounted on a distal 
end portion 38 of the second lead 14. 
The second lead 14 has a proximal end 39 mounting a terminal assembly 40 
which has a terminal pin 42. The terminal assembly 40 is received in a 
socket 43 in an implanted neural stimulator 44 for electrically connecting 
the terminal pin 42 to electrical circuitry within the neural stimulator 
44. 
As will be described in greater detail hereinafter, once it is determined, 
such as by testing, which one or ones of the ring electrodes 21-24 in the 
distal end portion 18 of the first lead 12 is best positioned for 
supplying stimulating current to nerve tissue, a selected ring electrode 
21, 22, 23, or 24 (identified such as by electrical conductivity testing) 
is connected through the connector assembly 16 to the terminal pin 42. 
In use, the distal end portion 18 of the first lead 16 is inserted into the 
epidural space in the spine of a body. Then, the proximal end portion 30 
of the first lead 12 is brought out of the body, as shown in FIG. 2, so 
that tests can be made by making connections, such as with alligator clips 
(not shown) between a conductivity sensor (not shown) and the sleeve 
electrodes 31-34 to determine the sensitivity or effectiveness of contact 
of each ring electrode 21-24 of the first lead 12 to the spinal cord. In 
this way, the ring electrode 21-24 which will be connected via connector 
assembly 16 to the terminal pin 42 is determined. 
Then the proximal end 30 of the first lead 12 is inserted on a rigid leg 90 
(FIG. 4) of the connector assembly 16 and a spring connector clip 92 is 
snapped over the sleeve electrode 32, 32, 33 or 34 connected to the 
selected ring electrode 21, 22, 23 or 24. 
Of course, before this is done a closure sleeve 100 (FIG. 3) is inserted 
over the proximal end portion 30 of the first lead 12 and far enough up on 
the lead 12 so that the proximal end portion 30 of the first lead 12 can 
be inserted on the leg 90 of the connector assembly 16. Then, after the 
clip 92 is connected to one of the sleeve electrodes 31-34, the closure 
sleeve 100 is slid back over the connector assembly 16 and sutures 102 and 
104 (FIG. 1) are tied around each end 106 and 108 of the sleeve 100 to fix 
the closure sleeve 100 over the connector assembly 16 and to seal the 
connections in the connector assembly 16 from body fluids. This is 
assisted by providing a bead 110 at the end 106 of the sleeve 100 and a 
bead 112 at the end 108 of the sleeve 100 for keeping each suture 102, 104 
(FIG. 1) on the sleeve 100 so it will not come off the respective end of 
the sleeve 100. 
Additionally, an annular rib 114 can be provided within a lumen 116 of the 
sleeve 100 adjacent the end 106 which is received over the first lead 12 
and a similar annular rib 120 can be provided in a larger lumen 122 of the 
sleeve 100 adjacent the end 108 of the sleeve 100 which is received over a 
cylindrical body 126 (FIG. 5) of the connector assembly 16 for providing 
an internal seal between the interior of the sleeve and the body 126 and 
the first lead 12. 
As best shown in FIG. 5, the connector assembly 16 of the present invention 
has the distal end portion 38 of the second lead 14 received in a bore 128 
in a tapered proximal end portion 130 of the body 126. A coiled wire 
conductor 131 in the second lead 14 extends from the proximal end portion 
38 where it is connected to the terminal pin into a finger 132 received in 
a stepped cavity 134 in the body 126. 
Within the stepped cavity 134 in the body portion 126, is positioned a 
cylindrical sleeve 136 made of a more rigid plastic material, such as a 
thermoplastic material. This sleeve 136 has an at least partially annular 
hollow 137 which receives an at least partially annular boss 138 of the 
finger 132 thereby to prevent relative longitudinal movement between the 
finger 132 and the cylindrical sleeve 136. 
Also, as shown in FIG. 5, the body portion 126 has, within the cavity 134, 
an annular rib 140 which is received in an annular groove 142 on the outer 
surface of the cylindrical sleeve 136 to prevent relative longitudinal 
movement between the body 126 and the cylindrical sleeve 136. 
The finger 132 is made of a flexible elastomeric material and has a bore 
143 opening onto a proximal end 144 of the finger 132 and extending to an 
internal end wall 145. An inner end portion 146 of the bore 143 is larger 
in diameter and has a metal sleeve 147 pressed into the inner end portion 
146. The coiled conductor 131 extends into the bore 143 and into the inner 
end portion 146 where a proximal end 148 of a wire conductor 149 is 
positioned between the sleeve 147 and a coiled end portion 150 of the wire 
conductor 131. Preferably, the sleeve 147, the wire end portion 148 and 
the coiled wire end portion 150 are soldered together. Alternatively, a 
pin 153 can be inserted as shown in FIG. 5 into the coiled end portion 150 
and the entire assembly can be crimped. 
The rigid leg 90 is integral with and extends axially outwardly from the 
cylindrical sleeve 136 adjacent a partially annular rib 151 at a distal 
end 152 of the sleeve 136. The rigid leg 90 is also made of a hard, stiff, 
rigid, thermoplastic material. 
As best shown in FIGS. 6 and 7, the rigid leg 90 has a partially 
cylindrical outer surface 154 and a flat inner or upper surface 156 with 
four saddle formations 161-164 extending upwardly from the flat surface 
156. The saddle formations 161, 162, and 163 are adapted to receive 
segments of the proximal end portion 30 of the first lead 12 between the 
spaced apart sleeve electrodes 31-34 thereon. 
The distal saddle formation 164, located at a distal end 166 of the rigid 
leg 90, includes a first jaw 168 (FIG. 8) and a second jaw 170 (FIG. 8) 
separated by a slot 172 (FIG. 8). The sides of the jaws 168, 170, facing 
each other on each side of the slot 172 have teeth 174, 176 (FIG. 8) 
thereon for gripping the proximal end portion 30 of the first lead 12, 
just distal of the proximal end portion 30 thereof, to assist in holding 
the proximal end portion 30 of the first lead 12 on the leg 90 of the 
connector assembly 16. 
The wire conductor 149 extends from its proximal end 148 into and through a 
flexible elastomeric sheath 180 which can be flexed and raised above the 
stiff rigid leg 90, as shown in FIGS. 2 and 4 to a distal end 182 which is 
fixed to the spring connector clip 92. 
As shown in FIGS. 6 and 7, the connector clip 92 includes a first leg 
portion 191, a second leg portion 192 having a free edge 193, and a bight 
portion 194. The first leg portion 191 has a connector leaf or blade 196 
integral therewith and extending upwardly generally parallel to the first 
and second leg portions 191 and 192 to a rounded curled over or bent end 
portion 197. The bare distal end 182 of the wire conductor 149 is received 
in the curled over or bent end portion 197 of the leaf 196 which is 
crimped over the uninsulated end 182 to make a mechanical and electrical 
connection therewith. 
The inside width of the U-shaped connector clip 92 is less than the outer 
diameter of each of the sleeve electrodes 31-34 so that an interference 
friction fit is made between the clip 92 and a selected one of the sleeve 
electrodes 31-34 when the clip 92 is brought down over the proximal end 
portion 30 of the first lead 12 and against the rigid leg 90. 
This is done, of course, after the sleeve electrodes 31-34 are aligned and 
in registry with the spaces between a distal end 200 of the body 126 and 
the saddle formations 161, 162, 163 and 164 on the leg 90. 
As shown schematically in FIG. 5, the first lead 12 has four insulated 
coiled wire conductors 201-204 therein. 
A wire conductor 201 in the proximal end portion 30 of the first lead 12 
has an uninsulated end portion that is brought out of the lead body 17 to 
make connection with the sleeve electrode 31. Likewise, the proximal end 
portions of wire conductors 202, 203, 204 are connected to sleeve 
electrodes 32, 33 and 34. 
In use, as described above, after the distal end portion 18 of the first 
lead 12 is inserted in the epidural space within the spine of a body, the 
sensitivity or conductive path between each of the ring electrodes 21, 22, 
23 and 24 and adjacent nerve tissues is determined by performing 
conductivity tests, such as by making selective connections to the sleeve 
electrodes 31, 32, 33 and 34 on the proximal end portion 30 of the first 
lead 12 which is withdrawn from the body for this purpose. 
Once the sensitivity or threshold level of each of the ring electrodes 21, 
22, 23 and 24 is determined, the closure sleeve 100 is inserted over the 
proximal end portion 30 of the first lead 12. Then the proximal end 
portion 30 of the first lead 12 is placed on the rigid leg 90 with the 
sleeve electrodes 31-34 in the spaces between the distal end 200 of the 
cylindrical sleeve 136 and the saddle formations 161-164. Then the 
connector clip 92 is squeezed over a selected one of the sleeve electrodes 
31, 32, 33 and 34. 
Then the closure sleeve 100 is moved over the leg 90 and the body 126 and 
the sutures 102 and 104 are tied in place to seal the closure sleeve 100 
about the body 26 and legs 91 and 92 of the connector assembly 16 and 
particularly about the first and second legs 90 with the proximal end 
portion 30 of the first lead 12 thereon. 
The sutures 102 and 104 are tied about the respective ends 106 and 108 of 
the closure sleeve 100 to seal the connector assembly 16, after which the 
connector assembly 16 is implanted within body tissue as shown in FIG. 1. 
From the foregoing description, it will be apparent that the 
multi-conductor neural stimulating assembly 10 of the present invention 
and particularly the connector assembly 16 thereof have a number of 
advantages some of which have been described above and others of which are 
inherent in the invention. In particular, the simple and easy way of 
connecting the proximal end portion 30 of the first lead 12 to the 
connector assembly 16 and the sealing of same enables testing of the 
sensitivity or threshold level of each ring electrode 21, 22, 23 and 24 
adjacent nerve tissue in the epidural space within the spine of the body 
prior to connection of the lead 12 to the lead 14. The stimulating 
assembly 10 is particularly adapted for relatively permanent implantation 
after testing has been effected with a temporary lead assembly of the type 
disclosed and claimed in copending application Ser. No. 042,834, filed on 
Apr. 27, 1987 for: MULTI-CONDUCTOR LEAD ASSEMBLY FOR TEMPORARY USE. 
Additionally from the foregoing description, it will be understood that 
modifications can be made to the neural stimulating lead assembly 10 of 
the present invention and the connector assembly 16 thereof without 
departing from the teachings of the present invention. For example, a 
second spring clip 92 can be provided as shown in FIG. 2 to provide a 
bipolar assembly. Accordingly, the scope of the invention is only to be 
limited as necessitated by the accompanying claims.