Skull mounted electrode lead securing assembly

Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical energy applicator

Reexamination Certificate

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C606S129000

Reexamination Certificate

active

06356792

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to a device used in the interventional treatment of neurological disorders, and more particularly to a novel electrode lead securing member which mounts to a burr hole in the patient's skull and prevents undesirable translation of the implanted lead as the external portion of the lead is manipulated during surgery.
2. Description of the Prior Art
The use of electrical stimulation of the brain for the purposes of alleviating pain and the treatment of other neurological afflictions has been utilized for a number of years, and in many instances has become the standard of care. The technique comprises the implantation of a long flexible electrical lead through a burr hole in the patient's skull, and into electrical contact with the pathological section of the patient's brain. The flexible lead comprises a plurality of long hetically wound wires encased in a elastomeric sheath. The distal end of the wire leads include electrical contacts and are placed in the brain. The proximal end of the wire leads remain external to the skull, and is coupled to an extension connector which joins the electrical wires to an electrical generator.
As is clear from the delicacy of the surgical field, it is critical to utilize robust instruments and implants which are not easily broken, and which do not lend themselves easily to unwanted movements. In particular, when an electrode lead is implanted, the position of the active tip is critical. The effects of the field generated by the electrical contacts is highly position dependent, and as a result, movement of the electrode after proper positioning can reduce or eliminate all effectiveness of the treatment. As it can be a very tedious process to find the appropriate location within the brain for the active tip, it is also critical that once the lead is situated, it should not be moved accidentally. Many of the subsequent manipulations of the external portions of the electrode leads, however, must be carried out after the active tip has been properly positioned. It is, therefore, a considerable concern that there be a means of securing the implanted portion of the electrode relative to the skull and the brain, while permitting the external portion to be moved freely. The additional feature which should be considered is that the surgeon should be able to easily manipulate any such securing device with ease, even when covered in slippery bodily fluids.
A device which is presently available in the art is illustrated in FIG.
1
. This device
10
is intended to hold a flexible wire lead
12
from moving, but is not designed to seat in a hole in the patient's skull. Rather, it is designed to be secured to soft tissue (for example in the vacinity of the spinal column). The use of this device is, therefore, intended to prevent gross movement of the electrode lead
12
. It is comprised of a first receiving member
14
which is cylindrical in shape. The lower portion of the cylinder forms a tapered hole
16
having an opening which is approximately the same diameter as the electrode lead
12
. A second inner seating member
18
fits within the receiving member, also having an axial bore through which the electrode lead passes. The tip
20
of the seating member
18
is thin-walled, such that the channel formed therethrough may deflect inward if compressed. The second, seating member is permitted to translate within the receiving member
14
from an an open position which permits the lead
12
to freely slide through the assembly, to a closed disposition in which the tip is forced into the narrowed end
16
of the bore of the receiving member
14
. In this position, the lead is friction locked in place by the compressed walls of at the tip of the seating member
18
. The exterior surface of the receiving member further includes a series of through holes
20
which permit the assembly to be secured to adjacent tissue by sutures. Unfortunately, the device is very difficult to manipulate in a surgical environment as it requires manual pushing and pulling of small members which are seated within one another, and which have no defined open and closed dispositions which demonstrably indicate that the electrode lead is truly secure.
A more directly related device which is presently available in the art is illustrated in
FIG. 2
, and is described in U.S. Pat. No. 5,464,446. It comprises a first port member
22
which is cylindrical and seats in the burr hole formed in the patient's skull
24
. The exterior lateral surface of the port includes a contoured circumferential flange portion
26
which is intended to form a seal with the inner lateral surface
28
of the burr hole. The upper portion of the port member includes an outwardly extending rim
30
which seats against the exterior surface of the skull
30
around the edge of the burr hole when the port is inserted fully in the burr hole. This upper contour is also designed to mate with a cap section
32
. The central axis of the seating member
22
forms a channel through which the electrode
34
seats and can slide prior to being locked in place. The cap
32
has a pair of channels formed therein; a first
36
which extends axially along the same direction as the axial passage in the port member, and the second
38
which extends out radially along the undersurface. The cap
32
engages the upper contour (and requires a suture
40
to hold the members together) in such a way that the electrode lead is compressed and is thereby locked in place. The use of a suture to secure the electrode, even indirectly, is a considerable drawback as it is difficult to manipulate, not easily reversible, and does not provide a readily obvious means for ensuring that the lead is truly secured against movements when the external portion is manipulated during the remainder of the surgery. Also, the compression lock, as in the first example is not easily viewed as it happens under the cap member.
The objects of the present invention are, therefore, clearly to provide an electrode securing assembly which reliably, easily, reversibly, and obviously locks an electrode lead to the skull, and most importantly, prevents the unwanted movement of the implanted portion of a deep brain stimulation lead during the manipulation of the external portion after the active internal tip has been properly positioned.
More specifically, it is an object of the present invention to provide an assembly which reliably mates with a burr hole in the skull and secures an electrical lead such that it does not move within the skull, but which permits free manipulation of the portion of the electrical lead which is external to the skull.
Simultaneously, it is also an object of the present invention to provide a mechanism which is easily manipulated by the surgeon under the conditions of the surgical field.
SUMMARY OF THE INVENTION
The preceeding objects of the invention are provided by the present device which comprises a first cylindrical port member which seats into a burr hole in the skull, and a second electrode lead locking member which is bayonet locked within the port member. More particularly, the port member includes an outer surface contour which grips the inner surface of the burr hole, and a laterally extending upper lip which seats against the outer rim of the burr hole in the patient's skull. The inner surface of the port member further includes a bayonet lock receiving structure, which generally comprises a pair of diametrically opposed recesses. Corresponding laterally extending elements on te external surface of the lead locking portion are provided to fit in these recesses such that but inserting and rotating the lead locking member, it is secured within the port member. Further, the second electrode lead locking member includes a central axial channel through which the electrode is passed, and which may slide through the channel freely prior to being locked therein.
The upper portion of the lead locking member includes a sliding e

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