Single and multi-polar implantable lead for sacral nerve electrical stimulation

An implantable medical lead for stimulation of the sacral nerves comprises a lead body which includes a distal end and a proximal end, and the distal end having at least one electrode contact having a length of between 0.10 and 1.50 inches extending longitudinally from the distal end toward the proximal end. The lead body at its proximal end may be coupled to a pulse generator, additional intermediate wiring, or other stimulation device. The implantable medical lead can comprise a first and second electrode contacts. The second electrode contact has a length of between 0.030 and 1.00 extending longitudinally from a point approximately 1.00 from the distal end toward the proximal end. The first and second electrode contacts do no overlap longitudinally. The implantable lead is implanted by taking the lead and implanting near the sacral nerves and then connecting to a pulse generator.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to an apparatus that allows for non-direct 
contact stimulation of the sacral nerves. More specifically, this 
invention relates to an implantable medical lead having at least one 
electrode contact wherein the lead is implanted near the sacral nerves for 
stimulation of a bundle of nerve fibers. Moreover, this invention relates 
to the method of implantation and anchoring of the medical lead near the 
sacral nerve to allow for non-direct contact stimulation. 
2. Description of Related Art 
Pelvic floor disorders such as, urinary incontinence, urinary 
urge/frequency, urinary retention, pelvic pain, bowel dysfunction 
(constipation, diarrhea), erectile dysfunction, are bodily functions 
influenced by the sacral nerves that can be treated using electrical 
stimulation. Specifically, urinary incontinence is the involuntary control 
over the bladder that is exhibited in various patients. Electrical 
stimulation of the sacral nerves can result in partial control over the 
evacuation function of the bladder and other related functions. Thus, for 
example, medical leads having discrete electrode contacts have been 
implanted on and near the sacral nerves of the human body to provide 
partial control for bladder incontinence. Other methods have been used to 
control bladder incontinence, for example, vesicostomy or an artificial 
sphincter implanted around the urethe. These solutions have drawbacks well 
known to those skilled in the art. In addition, some disease states do not 
have adequate medical treatments. 
In one current method of treatment for incontinence using electrical 
stimulation, two stimulation systems are implanted and have an implantable 
lead with discrete electrodes positioned directly on selected sacral 
nerves for sphincter and bladder stimulation respectively. The leads are 
connected to a pulse generator wherein an electrical stimulation pulse is 
transmitted. The sphincter is stimulated to prevent incontinence. When it 
is desired to evacuate the bladder, the electrical pulse to the sphincter 
is closed and the electrode connected to the bladder function is 
stimulated. After a delay, the bladder system stimulation is discontinued 
and the sphincter is again stimulated. A system and method for inserting 
an electrical lead within a human for applying electrical stimulation to 
the sacral nerves for control of incontinence and other related functions 
is discussed in U.S. Pat. No. 4,771,779 issued to Tanagho et al., and 
herein is incorporated by reference. 
Incontinence is primarily treated through pharmaceuticals and surgery. Many 
of the pharmaceuticals do not adequately resolve the issue and can cause 
unwanted side effects and a number of the surgical procedures have a low 
success rate and are not reversible. Typically, existing leads have four 
small discrete electrodes built into the distal end of the lead. During 
implantation, the physician steers the implantable pulse generator outputs 
to the electrodes to provide the most efficacious therapy. 
Unlike other surgical procedures, sacral nerve stimulation using an 
implantable pulse generator is reversible by merely turning off the pulse 
generator. The current electrical designs used for sacral nerve 
stimulation are not optimized for the application. Additionally, due to 
the small size of the stimulation electrodes, up to 0.060 inches, 
physicians spend a great deal of time with the patient under a general 
anesthetic placing the leads. The patient is thereby exposed to the 
additional dangers associated with extended periods of time under a 
general anesthetic. The current lead design used for sacral nerve 
stimulation uses 4 electrodes. Each electrode has a length of 0.030 inches 
and are spaced by 0.030 inches. Another lead that is currently used has 
electrodes 0.060 inches spaced by 0.060 inches. 
A problem associated with the prior art electrical stimulation to control 
incontinence is positioning and maintaining the discrete electrode in 
casual contact or in close proximity to the nerve to provide adequate 
stimulation of the sacral nerves. Another problem is constant or 
consistent stimulation. Accordingly, there remains a need in the art for 
an implantable electrical lead that allows for stimulation of a bundle of 
nerves and allows for some movement after implantation. 
SUMMARY OF THE INVENTION 
The present invention recognizes and provides a solution to the problems 
associated with implanting and maintaining electrical leads in close 
proximity or casual contact with discrete nerve fibers of the sacral 
nerves by providing a unique solution that allows implantation near the 
sacral nerves. Additionally, the invention provides a method of implanting 
a medical electrical stimulation lead for control of incontinence by 
stimulating a bundle of nerve fibers of the sacral nerve. Briefly, the 
present invention comprises a lead with at least one electrical contact 
extending for a length of between 0.10 and 1.50 inches. 
Accordingly, an object of the present invention is to provide for a unique 
implantable medical electrical stimulation lead that provides adequate 
stimulation of the sacral nerves for control of incontinence and other 
pelvic floor disorders without direct contact with the sacral nerves and 
with less sensitivity to placement. The unique lead simplifies the implant 
procedure and reduces or eliminates the need to reprogram the implantable 
pulse generator stimulation levels or re-open the patient to move the 
lead. 
Another object of this invention is to provide an implantation method for 
more rapid placement of medical electrical leads for the treatment of 
incontinence whereby the lead is placed near the sacral nerves. Implanting 
the medical electrical lead near the sacral nerves with less specificity 
as to location near the sacral nerves reduces the time for implantation. 
Currently, the implantation procedure for existing medical electrical 
leads stimulating the sacral nerve fibers takes approximately 20-60 
minutes. The current invention allows for implantation near the sacral 
nerve bundle and reduces the time for implantation to approximately 5-10 
minutes. The larger electrode of this invention creates a wider electric 
field which allows the lead to be placed in a less precise or gross manner 
while still providing adequate electrical stimulation to the sacral nerve. 
Yet another object of this invention is to provide a medical electrical 
lead and method of implantation whereby the lead can allow for some 
movement of the lead without deteriorating the capture of the sacral 
nerves. Because the electrode does not need to be in direct contact with 
the nerve fibers and due to the large electrode area, a small amount of 
movement from the original implant position does not reduce the nerve 
capture. 
A further object of this invention is to provide a medical electrical lead 
for stimulating the sacral nerves having a smaller than typical diameter. 
Providing the medical electrical lead with a smaller diameter may allow 
for alternate less invasive implantation techniques such as the use of a 
cannula. The smaller diameter medical electrical lead provides less trauma 
to a patient during implantation. Using this system for implantation may 
allow the physician to use a local anesthesia instead of a general 
anesthesia thus reducing the dangers inherent with the use of a general 
anesthetic. 
The full range of objects, advantages, and features of this invention are 
only appreciated by a full reading of this specification and a full 
understanding of the invention. Therefore, to complete this specification, 
a detailed description of the invention and the preferred embodiments 
follow, after a brief description of the drawing wherein additional 
objects, advantages and features of the invention are disclosed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, an implantable medical lead 10 that allows for 
non-direct contact stimulation of the sacral nerves comprises a lead body 
15 having at least one electrode contact 20 and a distal end 25. The 
electrode contact 20 extends longitudinally for a length of between 0.10 
inches and 1.50 inches from the distal end 25 toward a proximal end 35. 
The distal end 25 of the lead body 15 may comprise a conductive tip 30. 
The construction of the lead body distal end 25 may also comprise a 
non-conductive tip 30. 
The proximal end 35 of the lead body 15 may be coupled to a pulse 
generator, additional intermediate wiring, or other stimulation device. An 
example of such a pulse generator is the Medtronic InterStim 
Neurostimulator Model 3023. The stimulation pulses produced by the pulse 
generator are carried from the pulse generator through the proximal end 35 
of the lead body 15 of the present invention toward the distal end 25 
having at least one electrode contact 20. 
The length of the electrode contact 20 in the preferred embodiment is 0.40 
inches in length. The current typical lead for stimulation of the sacral 
nerves includes a discrete electrode. The larger electrode contact 20 of 
this invention generates a larger electric field for stimulating the 
sacral nerve. The larger electric field makes it easier to stimulate the 
nerve bundle. Because this medical lead 10 does not require the 
specificity of location of current leads, the implantation process is 
simplified. 
In the preferred embodiment, the electrode contact 20 is made of a solid 
surface material. Examples of solid surface materials are platinum, 
platinum-iridium, and stainless steel. The electrode contact 20 may also 
be made up of a coiled wire. The electrode contact material is selected 
based on the forming and corrosive properties of the material when 
subjected to the conditions within the human body. 
The lead body 15 of the present invention comprises one or more conductor 
wire(s) within an insulating sheath. The conductor material is preferably 
an MP35N alloy. The lead body 15 insulation material is preferably 
polyurethane or silicone. Other suitable materials known to those in the 
art may also be used. A typical diameter of the lead body 15 is 0.050 
inches but a smaller diameter is also acceptable. 
Referring to FIG. 2, the implantable medical lead 10 of the present 
invention may have an anchoring mechanism 50 to fixate the medical lead 10 
in the desired position. The anchoring mechanism 50 is a molded part, 
integral to the medical lead 10, where the physician can pass the sutures 
through the molded part to attach the medical lead 10 to the human 
anatomy. The anchoring mechanism 50 has at least one through hole, shown 
in FIG. 2, that allows the medical lead 10 to be inserted through the 
anchoring mechanism before adhering to the body. Another anchoring 
mechanism 50 is adapted to allow the use of a bone screw to screw to 
adhere the lead to the sacrum. Another anchoring mechanism 50 includes 
attaching an anchor to the medical lead 10 during the implantation 
procedure to allow the physician to suture to the anatomy. Yet another 
anchoring mechanism 50 is to allow the medical lead 10 to fibrose in 
naturally using the human body's natural reaction to a foreign body or 
healing. A further anchoring mechanism 50 is to use enzyme glues to 
provide the necessary anchoring. 
Turning to FIG. 3, the medical lead 10 of the present invention may have 
two electrode contacts 20 and 40. As above, the first electrode contact 20 
is preferably 0.40 inches in length. The second electrode contact 40 is 
preferably 0.60 inches in length. The length of the first and the second 
electrode contacts 20 and 40 extend longitudinally from the distal end 25 
toward the proximal end 35. The first electrode contact 20, as above in 
the single electrode embodiment, begins at the distal end having either a 
conductive or a non-conductive tip 30. The second electrode contact 40 
extends for a length starting at approximately 1.00 inch from the distal 
end 30 toward the proximal end 35. The first electrode contact and the 
second electrode contact do not overlap. The second electrode contact 
extends from a point beyond the end of the first electrode contact toward 
the proximal end. The length of the second electrode contact 40 is 
preferably 0.60 inches but may range between 0.03 and 1.00 inches. The 
length of the second electrode contact 40 must be large enough that the 
current density is not at a level that causes damage to the tissue or that 
may be sensed by the patient. 
As above, the first and second electrode contacts 20 and 40 can be made of 
a solid surface material, for example platinum, platinum-iridium, or 
stainless steel. The first and second electrode contacts 20 and 40 may 
also be constructed of a coiled wire. Another alternative embodiment of 
the medical lead 10 includes the first electrode contact 20 comprising a 
solid surface material and the second electrode contact 40 comprising a 
coiled wire. A coiled first electrode contact 20 may be preferred from a 
physiological standpoint whereas a solid second electrode may be preferred 
from a manufacturing perspective. The preferred embodiment will have a 
coiled first electrode contact 20 and a solid surface material second 
electrode contact 40. Where two electrodes are used, the first electrode 
contact 20 will be one polarity and the can of the implantable pulse 
generator will be the other polarity. In some instances, where the patient 
has pain at the implantable pulse generator site caused or increased by 
the stimulation, the second electrode contact 40 would be used instead of 
the can of the implantable pulse generator, thus eliminating the pain at 
the implantable pulse generator site. The first and second electrode 
contacts 20 and 40 are sized such the first electrode contact 20 does not 
longitudinally overlap with the second electrode contact 40. 
In FIG. 4, the implantable medical lead 10 may include an internal cavity 
60 shaped to accept a stylet 70. The stylet 70 is inserted into the lead 
body internal cavity 60 prior to implantation. The stylet 70 is made of 
solid wire such as tungsten or stainless steel. By inserting a stylet 70 
into the lead body internal cavity 60, the medical lead 10 is stiffened to 
provide support to the lead body 15 during implantation. Use of a medical 
lead 10 with a stylet 70 is particularly useful for implantation using a 
cannula. 
Turning to FIG. 5, the stylet 70 can alternatively have a manufactured 
shape. Various shapes of the stylet distal end 80 could be used to assist 
or guide the placement of the medical lead 10 to the optimal physiological 
position. An alternative shape of the stylet 70 includes a curved distal 
end 80. The medical lead 10 may also be manufactured with a pre-bent 
optimized shape to accept the stylet 70. With a pre-bent medical lead 10, 
a stylet 70 may or may not be used to assist in the implantation of the 
lead. A stylet 70 with a straight distal end 80 may be used to straighten 
the lead for passing through the cannula. The construction of the lead 
must be adapted to accommodate the stylet 70 to ensure that the stylet 70 
does not rupture the insulation on the electrical conductors. 
FIG. 6 shows an overall schematic of the sacral nerve area with a medical 
lead 10 implanted near a sacral nerve for stimulation. The implantable 
medical lead 10 is inserted by first making an incision appropriate to the 
size of the patient and then splitting the paraspinal muscle fibers to 
expose the sacral foramen. The physician then locates the desired position 
and inserts the medical lead 10 into the foramen and anchors the medical 
lead 10 in place. The medical lead 10 should be placed close enough to the 
nerve bundle that the electrical stimulation results in the desired 
physiological responses. The desired effect varies depending on which 
pelvic floor disorder is being treated or which nerve is being stimulated. 
The preferred position for the medical lead 10 is implantation parallel 
with the nerve. The parallel placement of the medical lead 10 to the nerve 
results in the most efficient transfer of electrical energy. With the 
medical lead 10 of this invention, the positioning is much less critical 
than current lead designs. 
To determine the best location of the lead, an insulated needle with both 
ends exposed for electrical stimulation is used to locate the foramen and 
locate the proximity of the nerve by electrically stimulating the needle 
using an external pulse generator. The location is tested by evaluating 
the physiologic response and by the electrical threshold required to get 
that response. Once the appropriate location has been determined using the 
insulated needle, the medical lead 10 is implanted in that approximate 
location. For control of incontinence, the physician preferably implants 
the medical lead 10 near the S3 sacral nerves. The implantable medical 
lead 10 may, however, be inserted near any of the sacral nerves including 
the S1, S2, S3, or S4, sacral nerves depending on the necessary or desired 
physiologic response. This invention can be used to stimulate multiple 
nerves or multiple sides of a single nerve bundle. In addition, the 
medical lead 10 can also be used as an intramuscular lead. This may be 
useful in muscle stimulation such as dynamic graciloplasty. Placement of 
the medical lead 10 of this invention does not require the specificity of 
current electrical stimulation of the sacral nerves. Additionally, the 
larger electrode contacts 20 and 40 make the present invention less 
susceptible to migration of the implantable medical lead 10 after 
implantation. 
The true spirit and scope of the inventions of this specification are best 
defined by the appended claims, to be interpreted in light of the 
foregoing specification. Other apparatus which incorporate modifications 
or changes to that which has been described herein are equally included 
within the scope of the following claims and equivalents thereof. 
Therefore, to particularly point out and distinctly claim the subject 
matter regarded as the invention, the following claims conclude this 
specification.