DE102007020377A1 - Instrument for stimulation and conduction of bioelectric signals in biological texture, has long stretched central body with cone point and flexible elements with opened electrode contacts, which are laterally connected with body - Google Patents

Abstract

The instrument has a long stretched central body with a cone point and flexible elements with opened electrode contacts (5), which are laterally connected with the body. The electrode contacts are electrically contactable over connection lines (6) in the elements and the body at the cone point relative to lying end of the body. The elements are formed in such a manner that in a relaxed condition elements are laterally away from the central body, and apply itself to the central body between the configuration of an internal voltage.

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 point and a plurality of exposed electrode contacts stimulation and / or dissipation of bioelectric signals can be done. Such instruments are used primarily 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 the stimulation and dissipation of electrical signals in vivo, suitable electrode systems must be implanted into the biological tissue. Out PJ Rousche et al., "A method for pneumatically inserting an array of penetrating cements into cortical tissue", Annals of Biomedical Engineering, Vol. 20 (1992), pages 413-422 It is known, for example, to implant a needle electrode array into the cortex at high speed by means of a pneumatic device. The high speeds of ≥ 8.3 m / s are required to bring all the needle electrodes of the array sufficiently deep into the tissue.

R. Eckhorn et al., "A novel 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 , describe a method for implanting fine fiber or needle electrodes, in which they are introduced separately from one another via a micromotor drive with increments of 1 micron in the tissue.

An instrument with an electrode system for stimulation and dissipation of bioelectric signals, in which the electrodes move and can be readjusted in the implanted state, is used 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 to move the electrodes. The movement is not continuous, but gradually with increments of 8.8 microns.

KC Cheung et al., "Flexible polyimide microelectrode array for in vivo recordings and current source density analysis", Biosensors and Bioelectronics (2006) , doi: 10.1016 / j.bios.2006.08.035 describe an implantable instrument having a needle-shaped body of a flexible polymer 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 μm 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 of tissue destruction in the area of the electrode contacts implanted in the tissue.

Presentation of the invention

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

The proposed instrument has an elongated or elongated central body with a point and laterally with the Body connected flexible elements on the exposed Wear electrode contacts. The electrode contacts are over Connecting leads in the elements and the body a tip of the body opposite the tip electrically contactable. In the proposed instrument are The elements are designed to be in a relaxed state protrude laterally from the central body and under construction Apply an internal voltage to the central body to let.

In one embodiment of the instrument, the elements are in the initial state of the instrument from the central body, so are in a relaxed state. Due to the penetration of the body into the tissue during implantation, the flexible elements then lay laterally against the central one Body, so that they are under a bias, the internal voltage. This bias results in a restoring force that wants to return the elements to their relaxed initial state. The elements present on the central body therefore slowly unfold again into their at least almost relaxed state, in which they protrude from the central body, as a result of the size of the restoring force and the counterforce caused by the tissue, as a result of the penetration of the central body into the tissue. As a result of this slow movement through the tissue, the tissue in the region of the electrode contacts is not damaged or damaged to a lesser extent than in the case of 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 so slowly relax or unfold into the tissue that the cells of the tissue by this unfolding or only slightly be damaged.

The Speed at which the elements unfold in the tissue or can relax about the geometry of these elements and whose material properties are adjusted, the size of the Determine preload. The size of the bias and thus the restoring force depends on chosen material and the thickness or the cross section of Elements and thus suitable in the manufacture of the instrument be determined. This size is dependent chosen from the tissue types of each 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. To describe eg. MA Howard et al., "Measurement of the Force Required to Move to a Neurosurgical Probe Through In Vivo Human Brain Tissue," IEEE Transactions on Biomedical Engineering, Vol. 46, No. 7 (1999), pp. 891-894 a measurement of the forces required to penetrate objects into the cortex.

at the above described embodiment of the instrument is exploited, that in the relaxed state of the central body protruding elements when penetrating the body in the Tissue initially automatically due to its flexibility Apply to the body and then slowly unfold into the tissue again until they are relaxed or approximate have reached a relaxed state. In a further embodiment The proposed instrument will increase the speed of deployment of the elements additionally influenced. These are the elements in the applied state of a layer of a biodegradable material covering them against the bias of the central body holds. After implanting the body in the Tissue is then passed through the layer of biodegradable material the contact with the tissue slowly degraded. By a thinner Formation of this layer in the region of the free ends of the elements these start after the appropriate dismantling or partial dismantling the thin layer to unfold first. In the course of the time, the thicker layer areas are biodegraded, so that the unfolding or relaxation process progresses can. In this way, the deployment speed can be of the elements about the sizing of biodegradable Control layer as well as the degradation properties of this layer. Especially can be a very slow with this configuration Unfolding of the elements and thus a very gentle penetration into reach the tissue.

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 Medications that, for example, inflammatory reactions in the Alleviate or inhibit tissue or cell adhesion of tissue cells reduce each other to facilitate penetration into the tissue.

The proposed instrument thus allows implantation of electrodes for stimulation and / or dissipation of bioelectric Signals in biological tissue with reduced tissue damage in the area of the exposed electrode contacts. This leaves the entire instrument during the operation implant, in which case the penetration of the elements with the electrode contacts in the tissue first slowly and continuously following the Operation is done.

The elements can in principle be designed in any geometric shape, as long as the application to the central body and the subsequent end deployment is achieved due to the material-related bias. Furthermore, the geometric shape of these elements must of course allow the integration of electrode contacts and associated connection lines. In the preferred embodiment, these elements are strip-shaped, ie they have a greater length than width and a smaller thickness than width. Here, length is to be understood as the distance between the end connected to the central body and the free end of the element or strip.

In One embodiment is the central body and the elements formed in one piece from the same material. This can For example, achieved by producing an elongated body are then laterally cut several times is to form the elements. The elements are then outward bent and in this state, for example by a tempering process, relaxed. A bending back of the elements then creates the desired preload for generating the restoring force, Slow the elements in the tissue against the resistance of the tissue moved outwards again. In such an embodiment The elements are positively in the applied state on the central body, because for them the corresponding dimensioned recesses are present. Such recesses can also be used in other embodiments of the central body provide. They facilitate the penetration of the body in the tissue.

The Of course, elements can also be separated made by the body 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

In the following, two exemplary embodiments of the proposed instrument will be 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 polymer, as shown by 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 to prevent. 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 made of 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

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 102004053596 A1 [0012]

Cited non-patent literature

• PJ Rousche et al., "A method for pneumatically inserting an array of penetrating cements into cortical tissue", Annals of Biomedical Engineering, Vol. 20 (1992), pages 413-422 [0002]
• R. Eckhorn et al., "A novel 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 [0003]
• 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 [0004]
• KC Cheung et al., "Flexible polyimide microelectrode array for in vivo recordings and current source density analysis", Biosensors and Bioelectronics (2006) [0005]
• 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. 46, No. 7 (1999), pp. 891-894 [0012]

Claims (10)

Instrument for the stimulation and / or dissipation of bioelectric signals in biological tissue, comprising an elongate central body ( 1 ) with a point and laterally with the body ( 1 ) 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 adapted to be in a relaxed state laterally of 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 claim 4, wherein 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.