DE102007020377B4 - Tissue-sparing instrument for stimulation and / or dissipation of bioelectric signals - Google Patents

Abstract

An instrument for stimulating and / or dissipating bioelectrical signals in biological tissue having an elongate central body (1) with a tip which allows a tissue-preserving penetration of the body into the tissue and flexible elements laterally connected to the body (1) 2) with exposed electrode contacts (5), which are electrically contacted via connecting lines (6) in the elements (2) and the body (1) at a tip end of the body (1), wherein the elements (2) so are formed so that they protrude in a relaxed state with one end laterally from the central body (1) and can be created by building an internal voltage to the central body (1).

Description

Technical application

The The present invention relates to an instrument for stimulation and / or Derivation of bioelectric signals in biological tissue, the an elongated central body with a tip and several having exposed electrode contacts via which the stimulation and / or Derivation of bioelectric signals can be done. such Instruments are mainly for the functional electrical stimulation as well as the derivation of bioelectric signals, for example in the central nervous system, used.

State of the art

For stimulation and derivation of electrical signals in vivo must be appropriate Electrode systems are implanted in the biological tissue. From P.J. Rousche et al., "A method for pneumatically inserting into an array of penetrating cortical tissue ", Annals of Biomedical Engineering, Vol. 20 (1992), pages 413-422 It is known, for example, a needle electrode array with the aid of a pneumatic Implant device at high speed into the cortex. The high speeds of ≥ 8.3 m / s are required to make all the needle electrodes of the array sufficient deep into the tissue.

R. Eckhorn et al., "A new method for the insertion of multiple microprobes into neural and muscular tissue, including fiber electrodes, fine wires, needles and microsensors ", Journal of Neuroscience Methods, 49 (1993), pages 175-179 Method for implanting fine fiber or needle electrodes, in which these separated from each other via a micro-motor drive with increments of 1 μm be introduced into the tissue.

One Instrument with an electrode system for stimulation and dissipation bioelectrical signals, in which the electrodes are implanted in the Move condition and readjustment is by J. Muthuswany et al., "An Array of Microactuated Microelectrodes for Monitoring Single-Neuronal Activity in Rodents ", IEEE Transactions on Biomedical Engineering, Vol. 52, no. 8 (2005), Pages 1470-1477, described. This instrument uses thermally based microactuators for moving the electrodes. The movement is not continuous, but gradually with increments of 8.8 microns.

The EP 0 783 900 A2 describes an implantable electrode cable assembly having a plurality of cables inserted into a lumen, such as a ventricle or atrium, for delivery of cardiac signals or for stimulation of the heart muscle via veins. At the destination, the exposed electrode contacts on the cables are pressed against the surrounding cavity wall with some bias. The contact pressure is maintained as long as by a cable at least partially surrounding stiffening, biodegradable material until the electrode contacts are embedded in the cavity wall.

Out DE 100 28 522 A1 For example, a cuff type neuroelectrode is known to be placed around a nerve such that one or more electrode surfaces make contact with the nerve through which electrical stimulation may occur. The neuroelectrode has an electrically insulated support which consists of a flat central element and laterally projecting, flat structural parts on which the electrode contacts are exposed. The flat structural parts are wrapped around the nerve during implantation. To stabilize the neuroelectrode during implantation, the electrically insulating support is connected to a support element which consists of biodegradablem material. The support element serves as an implantation aid and is absorbed by the body within a few days or weeks and replaced by biological tissue.

Out DE 10 2004 035 987 A1 For example, a fixation device for an implantable electrode or a catheter is known, which has a fixing element and a protective element. The fixing element serves to fix the electrode in the implanted state and has sharp structures. The existing of a biodegradable material protective element surrounds the fixing in the non-implanted state, so that unwanted injuries of z. B. blood vessels can be avoided. At the destination, the protective element is largely on.

KC Cheung et al., "Flexible polyimide microelectrode array for in vivo recordings and current source density analysis", Biosensors and Bioelectronics (2006), Vol. 22 describe an implantable instrument having a needle-shaped body of a flexible polymeric material carrying a plurality of exposed electrode contacts , The electrode contacts can be contacted via connecting lines at the rear end of the needle-shaped body. Investigations with this instrument, also referred to as neuroelectrodes, showed that the tissue reaction to the penetration of the neuroelectrode into the brain can be divided into two areas. Immediately after penetration, a 100 μm thick layer of astrocytes and microglial cells is formed within a few hours, the reaction being proportional to the cross-sectional area of the invaded body. This early reaction turns into a long term response after about seven days, during which a compact, some 10 microns thick layer forms. The long-term response is independent of the nature of the instrument. However, it is undesirable to form the thick layer in the region of the electrode contacts which forms immediately after the penetration due to tissue destruction since it can severely hinder the use of the individual electrodes.

The It is therefore an object of the present invention to provide an instrument for stimulation and / or dissipation of bioelectric signals in biological tissues, with a lower Measure tissue destruction implanted in the area of the electrode contacts in the tissue.

Presentation of the invention

The Task is solved with the instrument according to claim 1. advantageous Embodiments of the instrument are the subject of the dependent claims or can be the following description and the embodiments remove.

The proposed instrument has an elongated or elongated central body with a lace, which is a tissue-preserving intrusion of the body in allows the tissue and laterally with the body unilaterally connected flexible elements, the exposed electrode contacts wear. The electrode contacts are via connecting lines in the elements and the body at one of the top opposite End of the body electrically contactable. In the proposed instrument are The elements are designed to be in a relaxed state stand with one end laterally from the central body and under construction an internal voltage to the central body.

The Elements of the instrument are in the initial state of the instrument from the central body so are in a relaxed state. By penetration of the body into the tissue during implantation, the flexible elements then lie down laterally to the central body so they under a bias, the internally built up voltage, stand. This bias results in a restoring force affecting the elements wants to bring back to their relaxed initial state. The at the central body adjacent elements therefore unfold after the intruder central body in the tissue depending on the size of the restoring force and the counterforce caused by the tissue slowly back up in their at least almost relaxed state, where they are from the central body stick out. This slow movement through the tissue will Tissue in the area of the electrode contacts is not or less than damaged at a rapid penetration.

The Elements are therefore designed in such a way that they are due to their internal tension after penetration of the central body in relax or unfold the tissue so slowly that the cells of the tissue are not or only slightly damaged by this unfolding.

The Speed at which the elements unfold in the tissue or relax, can over set the geometry of these elements and their material properties Be the size of the bias determine. The size of the bias and thus the restoring force is dependent on selected Material and the thickness or the cross section of the elements and can thus be suitably determined in the manufacture of the instrument. This size will dependent on selected from the tissue types of the particular application, such as muscle tissue, Connective tissue or nerve tissue.

The proposed instrument makes use of the finding that very slow penetration into the tissue leads to a lower degree of tissue destruction. So is, for example, from the DE 10 2004 053 596 A1 a method for cell-sparing manipulation of individual cells is known in which a cell damage is avoided by a very slow speed of manipulation. The cells are given enough time to rearrange themselves. By setting a very slow rate of deployment of the elements at the central body, which is smaller than the rearrangement rate of the cytoskeleton of the cells and, for example, <500 .mu.m / h, preferably <300 .mu.m / h, thus the tissue destruction during penetration of the electrode contacts supporting elements in the tissue are significantly reduced. The forces required for tissue deployment can be measured in advance. For example, MA Howard et al., "Measurement of the Force Required to Move to a Neurosurgical Probe Through In Vivo Human Brain Tissue," IEEE Transactions to Biomedical Engineering, Vol. 7 (1999), pages 891-894, a measure of the forces required for the intrusion of objects into the cortex.

In the above-described embodiment of the instrument is exploited that the emerging in the relaxed state from the central body elements when investing the body in the tissue initially create due to their flexibility automatically to the body and then unfold slowly into the tissue again, until they relaxed or have reached approximately relaxed state. In a further embodiment of the proposed instrument is the speed the development of the elements is additionally influenced. For this purpose, the elements are covered in the applied state of a layer of a biodegradable material, which keeps them against the bias of the central body. After implanting the body into the tissue, the layer of biodegradable material is then slowly degraded by contact with the tissue. Due to a thinner formation of this layer in the region of the free ends of the elements, these begin to develop after the corresponding degradation or partial degradation of the thin film to be the first. Over time, the thicker layer areas biodegrade, so that the unfolding or relaxation process can progress. In this way, the rate of deployment of the elements via the dimensioning of the biodegradable layer and the degradation properties of this layer can be controlled. In particular, a very slow unfolding of the elements and thus a very gentle penetration into the tissue can be achieved with this embodiment.

In a development of this embodiment are in the biodegradable Layer bioreactive materials incorporated, which are associated with the degradation of Layer are released. This may be in particular Drugs that, for example, inflammatory reactions in the tissue alleviate or inhibit cell adhesion of tissue cells to each other reduce to facilitate penetration into the tissue.

The thus proposed instrument allows an implantation of electrodes for stimulation and / or dissipation bioelectrical signals in biological tissue with reduced tissue damage in the area of the exposed electrode contacts. Here you can also the entire instrument during implant the surgery, in which case the penetration of the elements with the electrode contacts in the tissue only slowly and continuously following the operation.

The Elements can be designed in principle in any geometric form, as long as the attachment to the central body and the subsequent unfolding due to the material-related bias is achieved. Farther Of course, the geometric shape of these elements must be the Integration of electrode contacts and associated connecting cables enable. In the preferred embodiment, these elements are strip-shaped, d. H. they have a greater length than Width and a smaller thickness than width. Under length is here the distance between the one connected to the central body End and the free end of the element or strip to understand.

In In one embodiment, the central body and the elements are made in one piece formed the same material. This can, for example, by making a long stretched body be achieved, the subsequent is laterally cut several times to form the elements. The elements are then bent outward and in this state, eg. through a tempering process, relaxed. A bending back The elements then produce the desired bias voltage for generation the restoring force, Slow the elements in the tissue against the resistance of the tissue back out emotional. In such an embodiment, the elements are in applied state form-fitting at the central body because, for they are the appropriately sized recesses available. Such recesses can also be used in other embodiments at the central body provide. They facilitate the penetration of the body into the tissue.

The Elements can of course, too separated from the body made and then connected to the body be, for example, by gluing or a galvanic technique.

Brief description of the drawings

The proposed instrument is described below by means of embodiments explained in more detail in conjunction with the drawings. Hereby show:

1 an example of the proposed instrument in a schematic representation in an initial state;

2 the instrument of 1 after penetration into the biological tissue;

3 the instrument of 1 in the implanted final state after unfolding of the elements;

4 another example of the proposed instrument in a schematic representation in an initial state;

5 the instrument of 4 in an intermediate state after implantation into the tissue; and

6 the instrument of 4 in the implanted final state after unfolding of the elements.

Ways to carry out the invention

The following are two exemplary embodiments of the proposed instrument described. 1 shows a schematic representation of a first embodiment of the instrument in an initial state. The instrument consists of a needle 1 as a central body, from the individual, with electrode contacts 5 occupied flexible stiffeners 2 bent outward in the relaxed state. The Stripes 2 are in the present example integral with the central needle 1 made of the same material. Be the stripes 2 to the needle 1 put on, so they are under a tension, which results in a restoring force, the stripes 2 wants to bring her back to her relaxed and unfolded state.

The individual electrode contacts 5 are each exposed in a known manner, ie not the material of the strips 2 covered to allow later direct contact with the tissue. This is not apparent in the figures. Furthermore, the electrode contacts 5 via connecting lines 6 at the end of the needle 1 contactable. This is only schematically based on the connection line 6 one of the electrode contacts 5 indicated. Of course you can do this on every strip 2 also several electrode contacts sit.

During implantation, the needle becomes 1 with the unfolded stripes 2 ie in the in 1 illustrated fir tree-like structure, in the biological tissue 3 pressed. When penetrating those with the electrode contacts 5 occupied strips 2 pressed back in, leaving her at the needle 1 issue. This state shows 2 , Because of the recesses for the stripes 2 at the needle 1 the strips are not over the surface of the needle in the applied state 1 above. By built up during application of internal tension acts a restoring force to the outside on the strips 2 , which at a very slow speed tissue-friendly outward into the tissue 3 suppressed. The speed of this deployment is about the material properties and the geometry of the strips 2 adjustable.

3 then represents the final state in the tissue in which the strips 2 with the electrode contacts 5 into the tissue 3 have penetrated and reached an approximately stress-free state of equilibrium.

The instrument of 1 to 3 is thus made up of the central needle 1 as well as the flexible elements or strips 2 with the electrode contacts 5 together, in the relaxed state branched from the central needle 1 out. These flexible, moving strips 2 are biased and move very slowly through the tissue under the influence of the restoring force. As a result, the destruction of tissue is reduced, so that fewer failures of the electrodes are to be expected by the reaction of the tissue. The speed of unfolding the stripes 2 can also be adjusted by the use of a slowly decomposing layer of a biodegradable or biodegradable material, for example. A biodegradable ble polymer, as based on 4 to 6 is explained.

4 shows a schematic detail view of a side of the proposed instrument after the penetration of the needle 1 into the tissue 3 , The adjacent stripes 2 are here of a layer 4 Made of a biodegradable polymer that covers the unfolding of the prestressed strips 2 prevented. This layer can be applied, for example, with a casting or dipping technique. The Stripes 2 are held, for example, by a suitable shape on the needle.

In this example, these stripes are 2 not parallel to the outside of the needle 1 but at a small angle in a recess of the needle 1 , The distance between the free ends of the strips 2 to the surface of the needle 1 this is less than the distance of the opposite end, with the needle 1 connected is. This leaves a layer 4 of the biodegradable material flush with the surface of the needle 1 on the stripes 2 Apply the layer thickness to the free end of the strip 2 decreased. This variation of the layer thickness is the time course of the unfolding of the strip 2 in the tissue 3 affected.

After penetration of the needle 1 into the tissue 3 the biodegradable polymer layer builds up 4 slowly. 5 This shows a transition state in which this layer 4 already partially degraded. By the variable in the axial direction of the needle thickness of the layer 4 at the outer end of the strip 2 was thinner, it has already completely degraded here, so that the outer part of the strip 2 due to the bias already in the tissue 3 has penetrated. As in this embodiment of the strip 2 is exposed slowly and continuously from the end, a slow and continuous penetration into the tissue by appropriate dimensioning of the layer thickness and choice of a suitable biodegradable material can be ensured.

6 then shows the final state where the biodegradable layer 4 completely degraded, leaving the strip 2 completely exposed and penetrated into the tissue. This in turn represents the almost completely relaxed and unfolded state of the strip 2 represents.

The needle 1 may be made of a biocompatible polymer, for example. Made of polyimide and for implantation in the cortex dimensions of, for example. 40 microns × 80 microns × 4 mm. The Stripes 2 are from the same polymer material as the needle 1 manufactured. As biodegradable material of 4 to 6 For example, with a suitable rate of degradation, polyorthoester can be used. Of course, however, other biodegradable materials can be used which have suitable degradation properties. The rate of degradation is chosen so that a penetration rate of the strip ends in the tissue of <300 microns / h is achieved.

1

needle

2

flexible strip

3

tissue

4

biodegradable polymer layer

5

electrode contacts

6

interconnectors

Claims (10)

Instrument for the stimulation and / or dissipation of bioelectric signals in biological tissue with an elongated central body ( 1 ) with a tip, which allows a tissue-preserving penetration of the body into the tissue, and laterally with the body ( 1 ) unilaterally connected flexible elements ( 2 ) with exposed electrode contacts ( 5 ), which are connected via connecting lines ( 6 ) in the elements ( 2 ) and the body ( 1 ) at a tip end of the body ( 1 ) are electrically contactable, wherein the elements ( 2 ) are formed so that they are in a relaxed state with one end laterally from the central body ( 1 ) and build up an internal tension on the central body ( 1 ). Instrument according to claim 1, in which the central body ( 1 ) lateral recesses for receiving the elements ( 2 ) in an applied state. Instrument according to claim 1 or 2, in which the elements ( 2 ) are formed strip-shaped. Instrument according to one of claims 1 to 3, in which the elements ( 2 ) of the same material as the central body ( 1 ) are formed. Instrument according to one of Claims 1 to 4, in which the elements ( 2 ) by incisions in the central body ( 1 ) are formed. Instrument according to one of claims 1 to 5, in which the elements ( 2 ) of a biodegradable layer ( 4 ) to the central body ( 1 ). Instrument according to claim 6, wherein the material and geometry of the biodegradable layer ( 4 ) are chosen so that the elements ( 2 ) with a by biodegradation of the layer ( 4 ) unfold predetermined speed. Instrument according to claim 6 or 7, wherein in the biodegradable layer ( 7 ) bioreactive materials, in particular drugs, are stored. Instrument according to one of claims 6 to 8, in which the biodegradable layer ( 7 ) is formed from a biodegradable elastic polymer. Instrument according to one of claims 1 to 9, in which the central body ( 1 ) is needle-shaped.