WO2008145765A2

WO2008145765A2 - Electrode and measuring device for measuring the electric activity in an electrically active tissue

Info

Publication number: WO2008145765A2
Application number: PCT/EP2008/056801
Authority: WO
Inventors: Detlef Behrend; Klaus-Peter Schmitz; Hans Wilhelm Pau; Katrin Sternberg; Wolfram Schmidt
Original assignee: Med-El Elektromedizinische Geräte G.M.B.H.
Priority date: 2007-06-01
Filing date: 2008-06-02
Publication date: 2008-12-04
Also published as: WO2008145765A3; DE102007026057A1

Abstract

The present invention relates to an electrode and a measuring device for measuring the action current and/or the action potential of an electrically active tissue. The aim of the present invention is to provide an electrode for measuring action currents and/or action potentials in electrically active tissues that can be produced in a simple and cost-effective manner that, on the one hand, guarantees a safe but reversible fixation of the electrode in the muscle tissue and, on the other hand, traumatizes the muscle tissue as little as possible. According to the invention, an electrode with an elongated electrode base body (1) having a first end (3) and a second end (4) is proposed, wherein the electrode is designed in a way, such that it can only be guided through a tissue (2) in a forward motion (6) along the longitudinal axis of the electrode basic body (1).

Description

Electrode and measuring device for measuring the electrical activity in an electrically active tissue

description

The present invention relates to an electrode and to a measuring device for measuring the action current and / or the action potential of an electrically active tissue, in particular the present invention relates to a monopolar stapedius muscle electrode for measuring the action potential generated in a contraction of the stapedius muscle.

The human ear can be subdivided into the areas outer ear (auricle), middle ear and inner ear. The middle ear consists of the eardrum and the ossicles hammer, anvil and stirrup. The eardrum is vibrated via the outer ear incoming sound waves. These vibrations can now be transmitted via the hammer, anvil and stirrup to the oval window of the inner ear, which in turn generates sound vibrations in the fluid of the cochlea. By the movement of the liquid, hair cells projecting into the cochlea are bent, triggering nerve impulses. In the middle ear, a mechanical impedance transformation takes place, which allows optimal transmission of the sound signal from the outer ear to the inner ear.

In addition, the eardrum muscle and the so-called stapedius muscle are located in the middle ear. The tympanic muscle is articulated to the hammer, with the stapedius muscle connected to the stirrup via a tendon. In the case of too high a sound pressure, which could damage the inner ear, both muscles contract reflexively, so that the mechanical coupling of the eardrum to the inner ear (and thus the power transmission) is reduced. This is a protection of the inner ear possible before too high sound pressure. The tension of the stapedius muscle, which is triggered by high sound pressure, is also called a stapedius reflex. From the diagnosis of the stapedius reflex it is possible to obtain medically relevant information about the functionality of the ear. Furthermore, the measurement of the stapedius reflex is useful for setting or calibrating so-called cochlear implants, since the sound sensed by a patient can be deduced from the measured stapedius reflex.

It is known to use electrodes for measuring the stapedius reflex, which are brought into contact with the stapedius muscle and forward the action currents or action potentials generated during a contraction of the stapedius muscle to a measuring device. In this case, a reliable, minimally invasive contacting of the stapedius muscle is difficult, since the stapedius muscle is arranged within a depression present in a bone and only the tendon of the stapedius muscle connected to the stirrup and its upper part are accessible from the interior of the middle ear.

From US 6,208,882 different stapedius muscle electrodes are known. However, these only reach an insufficient contact of the stapedius muscle tissue (especially in muscle contraction) and continue to be highly traumatizing.

It is therefore an object of the present invention to provide a simple and inexpensive producible electrode for the measurement of action currents and / or action potentials in electrically active tissues (preferably the stapedius muscle tissue), on the one hand ensures a secure, but reversible fixation of the electrode in the muscle tissue and on the other hand the muscle tissue as little traumatized as possible. These objects are achieved by the features of claim 1. Advantageous embodiments of the invention are contained in the subclaims.

According to the invention, the electrode has an elongated electrode base body having a first end and a second end, wherein the electrode is formed such that it can be guided through a tissue only in a forward direction along the longitudinal axis of the electrode body. Preferably, the electrode body has means for permanently or temporarily mechanically blocking the movement of the electrode through a tissue in a backward direction along the longitudinal axis of the electrode body. Thereby, a backward sliding out (backward movement) of the electrode can be avoided. Thus, a tissue-preserving fixation of the electrode is possible. After the measurement of the muscle activity, the electrode according to the invention can be removed in a simple manner by moving it further in the forward direction through the tissue and thus removing it from the tissue. In contrast, conventional electrodes are removed from the tissue at the back. Therefore, there is no sense in (mechanical) blocking the movement of the electrode in the backward direction along the longitudinal axis.

Preferably, the electrode body is flexible and has at least one passive or active fixing element. Preferably, at least three passive or active fixing elements are circumferentially arranged on the Elektrodengrund- body and the fixing elements are arranged from one another at the same angle in a plane perpendicular to the longitudinal axis (evenly distributed).

In a particularly preferred embodiment of the invention, the at least one fixing element is formed by a hook or by a spring. Alternatively, it is preferred that the electrode main body has a hollow channel for supplying a gas or a liquid into an airtight / liquid-tight interior of the at least one fixing element, wherein the position of the at least one fixing element with respect to the electrode base body via the internal pressure of the at least one fixing element is variable , Preferably, the distance of a distal end of the electrode body from the at least one fixing element on the internal pressure of the at least one fixing element is variable. As a result, after insertion of the electrode into the tissue, the position of the fixing elements can be adjusted by supplying a gas or a liquid via the hollow channel of the electrode base body in such a way that movement of the electrode base body along the longitudinal axis is blocked. For example, it is possible to spread the fixation elements by supplying a gas or a liquid from the electrode base body, so that they engage in the surrounding tissue and thereby block movement of the electrode base body along the longitudinal axis. After the measurement, it is then possible to reduce the internal pressure and thus to allow the movement of the electrode base body along the longitudinal axis to remove the electrode again.

Preferably, the at least one fixing element is elastic and / or resilient. Preferably, the at least one fixing element is connected to the electrode base body at a first end, wherein a second end of the fixing element is arranged to be freely movable in a plane which comprises the longitudinal axis of the electrode base body. Preferably, the at least one fixing element is pivotally arranged in an angular range between 15 ° and 75 °.

In a further preferred embodiment of the invention, the at least one fixing element is cylindrical or conical. Preferably, the at least one fixing element has a longitudinal extent of 0.5 to 1.0 mm and / or a diameter of 0.1 to 1.0 mm. According to a further preferred embodiment variant of the invention, it is provided that the at least one fixing element consists of a shape memory alloy, preferably NiTi. The fixing element preferably consists of a material from the group CrCoMo, Pt, PtIr, NiTi, Ti and TiAl4V6. The use of shape memory alloys allows not only high elasticity but also the use of shape memory. The necessary temperature can be supplied by an electric heater (the electrode itself as resistance wire) or body heat (max 37 ° C). A removal of temperature is preferably not controlled, but by body fluid, eg circulation, to 37 ° C, if it was previously higher. It is therefore possible, for example, abzuspreizen the fixing elements by supplying heat from the electrode body, so that they engage in the surrounding tissue and thereby block movement of the electrode body along the longitudinal axis. After the measurement, it is then possible to reduce the temperature of the fixing elements (active or passive by heat transport to surrounding tissue or body fluid) and thus to allow the movement of the electrode body along the longitudinal axis to remove the electrode again. Preferably, the electrode has a means for heating the at least one fixing element.

Preferably, the electrode base body is cylindrical (or hollow cylindrical). Preferably, the elongated electrode base body has a diameter of 0.1 mm to 2.0 mm.

The electrode base body preferably has an axial bending stiffness between 2 to 55 N mm ² (more preferably 20 to 30 N mm ² ) and more preferably 25 N mm ² . The fixing elements are preferably arranged in the range between 5 to 40% of the length of the electrode base body relative to the distal tip of the electrode base body (more preferably 10 to 20%) and more preferably 15%. According to a further preferred embodiment of the invention, it is provided that the at least one fixing element or the electrode base body in the region of the at least one fixing element has a temporary, water-soluble adhesive bond. Preferably, the water-soluble adhesive is a biocompatible adhesive based on peptide or polyurethane. Preferably, the water-soluble adhesive composition is disposed on the electrode (in an amount / concentration) such that the water-soluble adhesive composition is dissolved by tissue fluid at a temperature of 30 ° to 40 ° within a time interval of 5 seconds to 2 minutes. The adhesive is used to attach the passive or active fixation elements to the electrode. The adhesive bond should be released after a few seconds to a maximum of 2 minutes to set up the fixing elements. The required liquid is free tissue fluid. It is therefore possible, for example, to fix the fixing elements by means of the temporary, water-soluble adhesive bond in such a way that they closely fit against the electrode base body and thus the movement of the electrode base body along the longitudinal axis is possible for insertion of the electrode into the tissue. After the passage of time, the adhesive bond dissolves, so that the fixing elements (brought into their normal position and therefore) are spread apart by the electrode body, so that they engage in the surrounding tissue and thereby block movement of the electrode body along the longitudinal axis. Then, the measurement can be made because there is a secure fixation of the electrode.

The elongate electrode main body preferably has a length of 1.0 mm to 5.0 mm (particularly preferably 1.8 mm to 2.2 mm).

According to a further preferred embodiment of the invention, it is provided that the electrode is formed as a monopolar electrode. The elongate electrode main body preferably has an electrically conductive core and an electrically insulating jacket. Preferably, the electrically conductive core of the electrode base body is exposed only in the region of the at least one fixing element. Preferably that is first end of the electrode body tapering tapered (tapered) formed. Preferably, the second end of the electrode body is frictionally and releasably connected by means of a resilient clamping connection with an electrically conductive connecting wire. Alternatively, however, it is also possible to form the electrode according to the invention as a bipolar electrode.

According to a further preferred embodiment of the invention, a measuring device for measuring the electrical activity in an electrically active tissue is disclosed, comprising: an electrode according to at least one of the aforementioned features, wherein the electrode is connected to an electrically conductive connecting wire, and wherein the connecting wire with a Voltage meter or a power meter is connected. Preferably, the electrode is non-positively and releasably connected by means of a resilient clamping connection with an electrically conductive connecting wire. The voltage measuring device is preferably designed to measure the electrical potential applied between the first electrode and the second electrode in the range from +100 mV to-100 mV (preferably +40 mV to -90 mV).

According to another aspect of the invention, there is disclosed a method for determining the action current and / or the action potential of a human electrically active tissue, wherein an electrode according to any one of the preceding features is introduced into the active tissue from a first direction and the movement of the electrode is mechanically blocked by the tissue along the longitudinal axis of the electrode body, subsequently measuring the action current and / or the action potential of the tissue, and subsequently pushing the electrode in the same direction in which it was pushed into the tissue through the tissue and thus removed ,

The invention will be explained in more detail below with reference to embodiments shown at least partially in the figures. Show it:

1 shows a measuring device according to the invention for measuring the

Action potential of a stapedius muscle in a schematic, perspective view, wherein the fixing elements of the electrode are outside of the stapedius muscle

(Insertion of the electrode),

2 shows a measuring device according to the invention for measuring the action potential of a stapedius muscle in a schematic, perspective view, wherein the fixation elements are located within the stapedius muscle (during the

Measurement),

Fig. 3a, 3b an electrode according to the invention with three circumferential, spread (unfolded) fixing elements in a schematic, perspective view and

4a, 4b, an inventive electrode with three circumferentially arranged, folded fixing elements in a schematic, perspective view.

1 shows the measuring arrangement according to the invention for determining the action potential of a stapedius muscle 2 in a schematic perspective view. The measuring arrangement according to the invention consists of a monopolar electrode which has an elongate, flexible electrode base body 1. Preferably, this main electrode body 1 consists of a hollow cylindrical, electrically conductive material which is electrically insulated from its surroundings by means of an insulating jacket. For introduction of the electrode base body 1 into the stapedius muscle 2, the first end 3 of the electrode main body 1 is preferably designed to be tapered. As a result, an atraumatic penetration into the muscle tissue 1 is possible; furthermore, the electrode base Body 1 with a pliers-like instrument easily tangible. The second end 4 of the electrode base body 1 is electrically connected to a voltage measuring device 10 via a preferably electrically insulated connecting wire 11. The isolated electrode base body 1 has one or more exposed areas (not shown), via which the potential within the stapedius muscle 2 can be measured by means of the tension measuring device 10. Since the electrode according to the invention is used in the present embodiment as a monopolar electrode, the action potential of the stapedius muscle, for example, against mass or against a reference potential 12 can be measured.

According to the invention, the electrode has at least one, but preferably a plurality of fixing elements 5. These fixing elements 5 are suitable for mechanically blocking the movement of the electrode main body 1 along its longitudinal axis (FIG. 2). In the present embodiment, the fixing elements 5 are hook-shaped and arranged circumferentially at an angle of 120 ° to each other. The first ends 8 are connected to the electrode main body 1 and the second ends 9 are freely pivotable. In a preferred embodiment of the invention, the fixing elements 5 are pivotable with respect to the longitudinal axis of the electrode base body 1 at an angle of 15 ° to 75 °.

To insert the electrode into the stapedius muscle 2 in the forward direction 6 along the longitudinal axis of the electrode base body 1, the hook-shaped fixing elements 5 fold tightly against the electrode base body due to the advancing movement through the tissue (FIGS. 4a and 4b). This means that the second ends 9 of the fixing elements 5 rest tightly against the electrode base body 1, and thus allow a simple advance of the electrode base body 1 into (or through) the tissue of the stapedius muscle 2.

In order to measure the electrical potential of the Spapediusmuskels 2 is a secure fixation of the electrode within the muscle is necessary. That's it The invention provides that the hook-shaped fixing elements 5 are spread apart within the stapedius muscle 2 and thus a movement of the electrode base body 1 is mechanically blocked along its longitudinal axis (FIGS. 2 and 3). As a result, a reliable measurement of the potential of the stapedius muscle 2 via the connecting wire 11 is possible. It is particularly preferred that the uncovered region of the electrode base body 1, via which the measurement of the potential takes place, is located in the region of the fixing elements 5 of the base body 1 (but not arranged on the fixing elements 5). The fixing elements 5 themselves do not have to be electrically conductive. A fixation or a spreading can be achieved in different ways, for example by movement of the electrode body in the backward direction 7, whereby the hook-shaped elements 5 due to their limited pivoting (of preferably 75 °) respect. The forward direction 6 are spread and to a blockage of the electrode to lead. A further, alternative possibility consists in spreading the fixing elements 5 consisting of a shape memory alloy (preferably also the electrode base body made of a shape memory alloy) by means of a corresponding heat supply in order to realize a mechanical blocking of the electrode main body 1. Another possibility is to fix the fixing elements 5 by means of a temporary, water-soluble adhesive before the measurement such that the second ends 9 of the fixing elements (as shown in Fig. 4a, 4b) tight (preferably at an angle less than 30 °) , Then, the electrode can be introduced together with the fixing elements 5 in the stapedius muscle 2. Due to the surrounding tissue fluid, the compound (triggered in time) is released and the fixing elements 5 are spread open, which leads to a mechanical blocking of the electrode in the stapedius muscle 2, whereby a secure fixation of the electrode and therefore a reliable measurement can be ensured. LIST OF REFERENCE NUMBERS

1 electrode body

2 electrically active tissue / muscle

3 first end of the electrode body

4 second end of the electrode body

5 fixing element

6 forward direction

7 reverse direction

8 first end of the fixing element

9 second end of the fixing element

10 voltmeter / ammeter

11 connecting wire

12 reference electrode / mass

Claims

claims

An electrode for detecting the electrical activity in an electrically active tissue (2), comprising an elongated

Electrode base body (1) having a first end (3) and a second end (4), wherein the electrode base body (1) has at least one fixing element (5), and wherein the electrode is formed so that it by a fabric (2) only in a forward direction (6) along the longitudinal axis of the

Electrode base body (1) can be guided, characterized in that the at least one fixing element (5) at a first end to the electrode base body (1) is articulated, wherein a second end of the fixing element (5) in a plane which the longitudinal axis of the

Electrode main body (1), is arranged pivotably in an angular range between 0 ° and 90 °.

2. An electrode according to claim 1, characterized in that the electrode base body (1) comprises means for permanent or temporary mechanical blocking of the movement of the electrode through a fabric (2) in a backward direction (7) along the longitudinal axis of the electrode base body (1).

3. Electrode according to one of the preceding claims, characterized in that the electrode base body (1) has at least three passive or active fixing elements (5) which are arranged circumferentially on the electrode base body (1).

4. An electrode according to one of the preceding claims, characterized in that the at least one fixing element (5) is formed by a hook or by a spring.

5. An electrode according to any one of claims 1 -3, characterized in that the electrode base body (1) has a hollow channel for supplying a gas or a liquid in an airtight / liquid-tight

Interior of the at least one fixing element (5), wherein the position of the at least one fixing element (5) with respect to the electrode base body (1) on the internal pressure of the at least one fixing element (5) is variable.

6. An electrode according to any one of claim 5, characterized in that the distance of one of the electrode base body (1) distal end of the at least one fixing element (5) on the internal pressure of the at least one fixing element (5) is variable.

7. Electrode according to one of the preceding claims, characterized in that the at least one fixing element (5) is elastic and / or resilient.

8. Electrode according to one of the preceding claims, characterized in that the at least one fixing element (5) to the longitudinal axis of the electrode base body (1) in the direction of the second end (4) of the

Electrode base body (1) is arranged pivotably in an angular range between 10 ° and 80 °.

9. An electrode according to one of the preceding claims, characterized in that the at least one fixing element (5) to the longitudinal axis of the electrode body (1) in the direction of the second end (4) of the electrode body (1) in an angular range between 15 ° and

75 ° is arranged pivotally.

10. Electrode according to one of the preceding claims, characterized in that the at least one fixing element (5) is cylindrical or conical.

11. Electrode according to one of the preceding claims, characterized in that the at least one fixing element (5) has a longitudinal extent of

0.5 to 1.0 mm and / or has a diameter of 0.1 to 1.0 mm.

12. Electrode according to one of the preceding claims, characterized in that the at least one fixing element (5) consists of a shape memory alloy.

13. An electrode according to claim 12, characterized in that the at least one fixing element (5) consists of a material from the group CrCoMo, Pt, PtIr, NiTi, Ti and TiAI4V6.

14. Electrode according to one of claims 12 and 13, characterized in that the electrode has a means for heating the at least one fixing element (5).

15. Electrode according to one of the preceding claims, characterized in that the electrode base body (1) is cylindrical.

16. Electrode according to one of the preceding claims, characterized in that the elongated electrode base body (1) has a diameter of 0.1 mm to 2.0 mm.

17. Electrode according to one of the preceding claims, characterized in that the at least one fixing element (5) or the electrode base body (1) in the region of at least one fixing element (5) has a temporary, water-soluble adhesive bond.

18. Electrode according to claim 17, characterized in that the water-soluble adhesive compound is a peptide based on peptide or Polyuhrethanbasis.

19. An electrode according to any one of claims 17 to 18, characterized in that the water-soluble adhesive compound is arranged on the electrode in an amount such that the water-soluble adhesive bond

Tissue fluid of a temperature of 33 ° to 40 ° within a time interval of 2 seconds to 10 minutes is released.

20. Electrode according to one of claims 18 to 19, characterized in that the water-soluble adhesive bond is arranged on the electrode in an amount such that the water-soluble adhesive bond Tissue fluid of a temperature of 33 ° to 40 ° within a time interval of 20 seconds to 2 minutes is released.

21. Electrode according to one of claims 17 to 20, characterized in that the water-soluble adhesive bond is arranged on the electrode in an amount such that the water-soluble adhesive bond by tissue fluid at a temperature of 33 ° to 40 ° within a time interval of 30 seconds to 1 minute is solved.

22. Electrode according to one of the preceding claims, characterized in that the elongated electrode base body (1) has a length of 1, 0 mm to 5.0 mm.

23. Electrode according to one of the preceding claims, characterized in that the elongated electrode base body (1) has a length of 1, 8 mm to 2.2 mm.

24. Electrode according to one of the preceding claims, characterized in that the elongated electrode base body (1) has an electrically conductive core and an electrically insulating jacket.

25. An electrode according to claim 24, characterized in that the insulation has a wall thickness between 2 and 30 microns and / or the insulation consists of a biocompatible elastomer.

26. An electrode according to any one of claims 24 and 25, characterized in that the electrically conductive core of the electrode base body (1) is exposed only in the region of the at least one fixing element (5).

27. An electrode according to claim 26, characterized in that the exposed area has an area of 0.01 to 12 mm ² .

28. Electrode according to one of the preceding claims, characterized in that the first end (3) of the electrode base body (1) is formed tapering and / or has a half or quarter circularly curved tip.

29. Electrode according to one of the preceding claims, characterized in that the second end (4) of the electrode base body (1) by means of a resilient clamping, plug or screw with an electrically conductive lead wire (11) is positively and releasably connected.

30. A measuring device for measuring the electrical activity in an electrically active tissue (2) comprising: an electrode according to any one of claims 1-29, wherein the electrode is connected to an electrically conductive lead wire (11), and wherein the lead wire (11) a voltage measuring device (10) or a current measuring device is connected.

31. Measuring device according to claim 30, characterized in that the electrode is non-positively and releasably connected by means of a resilient clamping connection with an electrically conductive connection wire (11).

32. Measuring device according to one of claims 30 and 31, characterized in that the electrode is designed as a monopolar electrode.

33. Measuring device according to one of claims 30 - 32, characterized in that the voltage measuring device (10) for measuring the voltage applied to the electrode electrical potential in relation to a

Reference potential (12) is designed.

34. Measuring device according to one of claims 30 - 33, characterized in that the voltage measuring device (10) is designed for measuring the voltage applied to the electrode electrical potential with respect to the zero potential (ground).