WO1995005117A1

WO1995005117A1 - Electrode assembly

Info

Publication number: WO1995005117A1
Application number: PCT/GB1994/001783
Authority: WO
Inventors: Iver Arne Langmoen
Original assignee: Medinnova Sf; Cockbain, Julian, Roderick, Michaelson
Priority date: 1993-08-17
Filing date: 1994-08-15
Publication date: 1995-02-23
Also published as: GB9317099D0

Abstract

There is provided a surgical implant apparatus, conveniently including an electrode assembly and electrical leads thereto but alternatively a fluid conduit, comprising a conduit means with attached thereto a skin piercing member, which conduit means if hollow is sealed at at least the end attached to said skin piercing member. In a preferred embodiment, the conduit (6) contains electrical leads (5) connecting electrical contacts (11) on the skin piercing member (7) to electrodes (3, 4) of an electrode array (1), with the skin piercing member itself taking the form of an electrical jack which is engageable with a receiving socket.

Description

Electrode Assembly

The invention relates to transcutaneous conduit means, in particular for intracranial electrode assemblies.

During surgery it is frequently desirable to implant within the body a device which has a transcutaneous conduit attaching it to apparatus outside the body. At its simplest, such a conduit may simply take the form of a hollow tube, catheter or cannula through which fluid may be introduced into the body from outside or through which fluid may be drained out of the body, for example for diagnostic testing, for treatment and return, or to relieve pressure build up. Other forms of conduit however include electrical leads for supply of power to or to transmit signals from devices surgically placed within the body.

While in all cases the conduit must pass through the skin, the aperture in the skin through which it passes may either be especially created for it or must exist already, e.g. as a result of accident or injury or as a result of the implantation of the device to which the conduit is connected. Thus in general either the conduit is passed through a pre¬ existing aperture which is subsequently closed up around the conduit or it is passed from outside the body through an aperture created for it.

In the latter case there is a substantial risk that the act of passing the conduit through the skin or the creation of the aperture for passage of the conduit will cause infection as a result of transfer into the body of pathogens present on the skin surface. This is particularly so where the skin surface is difficult to sterilize or where the organ or tissue into which the conduit is passed is particularly prone to infection as is the case for instance with electrodes implanted within the brain.

In the treatment of epilepsy it is now well established that the patient may respond to surgical excision of brain regions which are foci of epileptic activity. Such foci may occur deep within the brain and to identify them electrodes or electrode strips capable of detecting electrical activity at a plurality of sites are implanted, generally in the sub-dural cavity beneath the brain.

Due to the danger of leakage of cerebrospinal fluid, the leads to such electrodes are generally taken through the skin at a site remote from the site at which the electrodes themselves are inserted. This is generally done by piercing a hole through the skin from the outside with a stiletto (needle) and drawing the leads out from the body through this hole. As mentioned above however this brings about the risk of infection from the skin surface, a risk which is particularly severe in the case of the brain.

Thus we now propose to provide a conduit for implantation into the body with a piercing means so that it can be thrust through the skin from the inside and drawn through from inside to outside thus reducing the risk of introducing infectious agents from the skin surface.

Viewed from one aspect the invention provides a surgical implant apparatus comprising a conduit means with attached thereto a skin piercing member, which conduit means if hollow is sealed at at least the end attached to said skin piercing member. The apparatus of the invention desirably has the interior of the conduit means sealed at the skin piercing member end. If the conduit contains an electrical lead however this will desirably be electrically connected to electrical contact means on the surface of the skin piercing member.

In the apparatus of the invention, which will of course be presented for use in sterile form, the conduit means is desirably attached at its end remote from the skin piercing member to an implantable device such as an electrode or electrode array. Alternatively, where the conduit is hollow, the end of the conduit means remote from the skin piercing member may simply be open to allow fluid to pass therethrough. The conduit means in the apparatus of the invention can itself take any suitable form although it will preferably comprise at least one electrical lead or at least one hollow fluid transfer conduit. In the latter case the skin piercing member will conveniently seal off the end of the conduit at which it is attached so that contamination of the interior of the conduit does not occur during passage through the skin. For subsequent use the skin piercing member or its tip may be removed or a needle may be inserted into a portion of the conduit external to the body to allow fluid transfer in or out of the body.

In a particularly preferred aspect however the conduit means comprises as least one electrical lead and while such leads may be detachable from the skin piercing member, it is especially preferred that this member should provide one or more corresponding electrical contacts for connection to apparatus external to the body, e.g. voltage detection or current supply apparatus. In this regard, it is particularly convenient for the skin piercing member to constitute an electrical jack or plug engageable with a receiving member to bring one or more electrical contacts on the piercing member into electrical contact with corresponding electrical contacts in the receiving member. In this way the skin penetration member, after passage out through the skin, may simply be plugged into a receiving socket in apparatus outside the body (after suitable wiping, cleaning and drying if desired) .

In a preferred embodiment the invention thus provides a surgically implantable electrode assembly comprising electrode means connected to a skin piercing member by an electrical lead, said skin piercing member having on its surface an electrical contact member electrically connected to said electrode means by said lead.

The skin piercing member will conveniently take the form of an elongate spike having a central core member provided at one end with a piercing means (e.g. a point or spike) and with one or more annular electrically conducting contact members dispersed along its length, preferably spaced apart by electrically non-conducting annular members, e.g. of a plastics material such as Teflon.

The core and the piercing means may be of unitary construction if desired, but if flexibility is required it will be preferred that the core be of a flexible material, e.g. plastics, while the piercing means will preferably be of hard material, e.g. metal or harder plastics. Where the core is itself electrically conducting, then it will generally be provided with a non-conducting sheath to isolate it electrically from one or more of the electrical contact members. In an alternative construction however the body of the skin piercing member may comprise a non-conducting matrix, with a plurality of laterally or circumferentially separated, axially extensive contact members embedded therein or carrying thereon a plurality of axially separated annular contact members.

The conduit means may be connected to the skin piercing member in any convenient manner, but where the conduit means are electrical leads these will, as indicated above, preferably be in electrical contact with a surface portion of the skin piercing member. Moreover such electrical leads will generally be provided along at least a portion of their length with an insulator coating.

To avoid infection or cerebrospinal fluid leakage it is desirable that the skin piercing member should be used to pierce the skin some centimetres away from the incision through which the conduit and any attached device are inserted for surgical implantation. Thus the skin piercing member will generally be so formed as to allow it to be moved subdermally before skin piercing occurs. While it may thus take an essentially needle-like or stiletto form with the skin piercing means on its tip, in an alternative embodiment the skin piercing means is provided as a flange so that skin piercing only occurs when the member having been pushed subdermally is then drawn back. The flange piercing the skin may be grasped, e.g. with tweezers, and the member and conduit drawn out through the hole thus formed in the skin. The skin piercing member will preferably be 2 to 15 cm long, especially 5 to 10 cm. Its minimum cross-sectional dimension, e.g. its diameter if it is of circular cross section, will conveniently be in the range of 1 to 5 mm, especially 2-4 mm. If it takes the form of a flat strip, the maximum cross-sectional dimension, i.e. the strip width, will conveniently be in the range 2 - 12 mm .

In the apparatus of the invention, the skin piercing member may be detachable from the conduit means and thus viewed from another aspect the invention provides an elongate skin piercing device having a skin piercing means and a plurality of surface electrical contact members each provided with electrical lead attachment sites.

The electrical lead attachment sites in the devices of the invention may comprise one part of a male-female socket but also may comprise a region, preferably an indentation, at which a lead may be attached by other conventional means, e.g. by soldering or by overlay of a curable adhesive or resin. Equally, where the contact members are annular rings disposed about a central core and separated by non-conducting rings, leads may be attached mechanically by placement between a connecting and a non-connecting ring and by axial compression of the rings, e.g. by tightening a screw or bolt in or on a threaded core.

For such skin piercing devices, the end of the conduit means remote from the skin piercing member may be or may be adapted to be connected to apparatus surgically implanted in the body, e.g. an electrode assembly. The nature of the device or the adaptation will of course depend on the purpose of the implant.

Preferred aspects of the invention will now be described by way of example and with reference to the accompanying drawings, in which:

Figure 1 is a perspective drawing of the intracranial electrode assembly according to the invention;

Figure 2 is a longitudinal sectional view of the skin piercing member in the assembly of Figure 1,- and

Figure 3 is a perspective view of an alternative skin piercing member for an electrode assembly as shown in Figure 1.

Referring to Figure 1 there is shown an intracranial electrode strip 1 comprising a flexible plastics strip 2 with disposed therein a plurality of electrode plates 3 each having an exposed metal surface 4 and each being electrically connected on the reverse side to an electrical lead 5. Intracranial electrode strips of this type are known and have been in use for several years. The electrical leads 5 are individually plastics coated between their extremities and are together encased in a plastics sheath 6 between electrode plates 3 and their junction to skin piercing member 7.

As shown in Figure 2, the skin piercing member comprises a conical steel spike 8 attached to a threaded core 9 which is provided with a plastics sheath 10. Alternatively disposed about core 9 are conducting 11 and non-conducting 12 annular rings of brass and plastics, the entire assembly being held together by nut 13 screwed onto the threaded end of core 9. Along the side of the skin piercing member is a channel 14 in which the electrical leads 5 are disposed, with the different leads being held in electrical contact with the different conducting rings by cured adhesive 15 also disposed within channel 12.

As shown, spike 8 and core 9 are of metal. However if greater flexibility is required these can be of plastics in which case sheath 10 may be dispensed with.

In the alternative embodiment shown in Figure 3, the skin piercing member is in the form of a strip 16 having conducting surface portions 17 and a backwards directed flange 18 which is pointed to provide the means for skin piercing on insertion between the skin and the skull and subsequent slight retraction. This configuration allows for careful positioning of the skin piercing flange before piercing occurs.

In use, the electrode strip and the attached lead are inserted into the cranial cavity through a first incision in the scalp from the edges of which the skin is peeled back to prevent contact with the strip and lead and with any of the surgical implements being used. The skin piercing member is then inserted between the peeled back skin and the underlying tissue and its spike is pushed out through the skin some centimetres away from the first incision. The skin piercing member and the connected lead are then drawn through the skin and the skin piercing member is inserted, as an electrical jack, into the electrical potential monitoring apparatus.

Claims

Claims :

1. A surgical implant apparatus comprising a conduit means with attached thereto a skin piercing member, which conduit means if hollow is sealed at at least the end attached to said skin piercing member.

2. Apparatus as claimed in claim 1 wherein said conduit means contains an electrical lead.

3. Apparatus as claimed in claim 2 wherein said conduit means is attached at its end remote from said skin piercing member to an implantable device.

4. Apparatus as claimed in claim 3 wherein said device comprises an electrode.

5. Apparatus as claimed in claim 3 wherein said device comprises an electrode array.

6. Apparatus as claimed in claim any one of claims 2 to 5 wherein said skin piercing member provides an electrical contact to said lead.

7. Apparatus as claimed in claim 6 wherein said skin piercing member is in the form of an electrical jack.

8. Apparatus as claimed in any one of claims 1 to 7 wherein said skin piercing member comprises an elongate spike having a central core member provided at one end with a piercing means and with at least one annular electrically conducting contact member disposed along its length.

9. Apparatus as claimed in claim 8 wherein said annular contact members are separated by electrically non-conducting annular members.

10. Apparatus as claimed in claim 1 wherein conduit means is hollow.