Medical device for use in pain treatment

Abstract

To provide a medical device for use in pain treatment, and use in pain treatment by nerve stimulation.SOLUTION: Such medical devices are known that include an invasive component having at least one electrode configured to be placed on a nerve and to emit an electrical stimulation signal, and a signal generator connected to the electrode and configured to generate a stimulation signal, the stimulation signal being configured to inhibit the impulse transmission of the nerve. According to the invention, the at least one electrode is configured to emit an electrical monitoring signal, the signal generator is configured to generate the monitoring signal, and the monitoring signal is configured to cause a motor and / or sensory response, the form of which is dependent on the distance between the electrode and the nerve.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a medical device for use in pain treatment, comprising an invasive component having at least one electrode positioned on a nerve and configured to emit an electrical stimulation signal, and a signal generator connected to the electrode and configured to generate a stimulation signal, the stimulation signal being configured to inhibit stimulation transmission in the nerve. [Background technology]

[0002] Such devices are known in the prior art and are used to treat acute or chronic pain, in that the transmission of nerve impulses is inhibited by the emission of an electrical stimulation signal in order to reduce the patient's pain sensation. For this purpose, an invasive part of the medical device is introduced into the body and electrodes disposed or formed on the invasive part are positioned near the nerve. An electrical stimulation signal is generated by a signal generator of the medical device and emitted via the electrodes.

[0003] The position of the electrode relative to the nerve to be stimulated is crucial for the achievable therapeutic effect. If the electrode is closer to the nerve during the stimulation procedure, the stimulation energy released at the nerve increases. If the electrode is further away, the stimulation energy thus acting on the nerve is reduced. This distance can change, and a concomitant change in stimulation energy can occur, for example, due to patient movement.

[0004] Methods for adjusting the emitted stimulation energy are already known from the prior art. These methods provide for tracking and correcting the stimulation energy and are used in the field of nerve stimulation within the spinal canal (SCS). For this purpose, for example, the "coupling" of the stimulation signal with the nerve and its reaction are measured. The stimulation energy of the electrical stimulation signal is adjusted accordingly.

[0005] The nerve response can only be measured in the case of direct contact of the two electrodes with the nerve. In the stimulation of peripheral nerves in the so-called single-shot technique, continuous contact of the electrodes with the nerve cannot be assumed. Summary of the Invention [Problem to be solved by the invention]

[0006] It is an object of the present invention to provide a medical device of the initially mentioned type that allows for improved pain treatment. [Means for solving the problem]

[0007] This objective is achieved in that at least one electrode is configured to emit an electrical monitoring signal, and a signal generator is configured to generate the monitoring signal, which is configured to generate a motor and / or sensory response, the form of which depends on the distance between the electrode and the nerve. The medical device according to the present invention thus enables the generation and emission of two signals: an electrical stimulation signal, on the one hand, and an electrical monitoring signal, on the other hand. The stimulation signal is used for the actual pain suppression in that it inhibits the transmission of stimuli in the affected nerve. The monitoring signal is used to monitor the position or otherwise distance of the electrode, in that it is configured to induce a motor and / or sensory response in the patient, the form of which depends on the distance between the electrode and the nerve. Depending on the form of the motor and / or sensory response, the medical personnel performing the pain treatment can recognize (or, in the case of a sensory response, the patient's own feedback) whether the electrode must be repositioned to enable optimal pain treatment. If the motor and / or sensory response is weak, further distal advancement of the electrode in the direction of the nerve will usually be necessary. If the motor and / or sensory response is strong or excessively strong, it will usually be necessary to retract the electrodes proximally to increase the distance. The form of the motor and / or sensory response may also depend on the intensity of the monitoring signal. If the motor and / or sensory response is strong or excessively strong, it may be necessary to adapt, particularly reduce, the intensity of the overall signal consisting of the stimulation signal and the monitoring signal. The actual electrical stimulation signal for pain suppression has specific characteristics, particularly electrical and / or signal transmission characteristics. These characteristics are known to those active in the relevant technical field, and explicit specificity of the stated characteristics is not necessary at this point. The electrical monitoring signal has different characteristics, particularly different electrical and / or signal transmission characteristics. In one embodiment, the invasive component is a catheter equipped with at least one electrode. In a further embodiment, the invasive component is a stimulation cannula equipped with at least one electrode. In a further embodiment, the invasive component is a wire, which in turn forms at least one electrode, or vice versa.In one embodiment, the medical device has a single electrode configured to emit both a stimulation signal and a monitoring signal. In a further embodiment, there are at least two electrodes, with a first of the two electrodes configured to emit a stimulation signal and a second of the two electrodes configured to emit a monitoring signal. Alternatively, or in addition, a first of the at least two electrodes can be used as a cathode and a second of the at least two electrodes can be used as an anode. The invasive component including the electrodes is configured to be introduced into the patient's body. In contrast, the signal generator is an extracorporeal component of the medical device connected by wire to at least one electrode of the invasive component. In other words, the signal generator is intended to remain outside the patient's body. In one embodiment, the medical device has a detection device configured to detect motor and / or sensory responses, and in particular their morphology, evoked by the monitoring signal. In a further embodiment, such a detection device is also configured to generate a signal in response to the detected morphology of the motor and / or sensory response, which represents the morphology of the motor and / or sensory response. The signal is preferably an acoustic or optical signal and / or a signal that is otherwise perceptible by the medical personnel, based on which the medical personnel can decrease or increase the distance of the nerve from the electrode. In a further embodiment, no such detection device is provided. Instead, some form of motor and / or sensory response is detected by the medical personnel themselves, for example, visually or tactilely and / or otherwise.

[0008] In one embodiment, the electrical stimulation signal is configured so as not to induce a motor and / or sensory response, especially one that is actually significant, and the monitoring signal is configured so as not to produce an inhibition of the stimulus transmission. In other words, in this embodiment, there is no crossover, or in any case no actually significant crossover, with respect to the physiological response produced by the associated signal. In this embodiment, the stimulation signal has a small, if any, effect on the motor and / or sensory response, which is undesirable. This prevents the monitoring signal from superimposing on the effect of the stimulation signal and thus damaging it in an undesirable way. Conversely, the stimulation signal is also prevented from damaging or corrupting the effect of the monitoring signal.

[0009] In a further embodiment, the stimulation signal is at least 0.5×10 slower than the frequency of the monitoring signal. 3 , preferably at least 1 x 10 3 , more preferably 1.5 × 10 3 In this embodiment, the stimulation signal has a frequency that is 1.5 times greater than the monitoring signal. Conversely, the monitoring signal has a frequency that is lower than the stimulation signal. Such frequency selection can prevent unwanted overlapping of physiological effects (inhibition of stimulus transmission on the one hand, and eliciting motor and / or sensory responses on the other hand).

[0010] In a further embodiment, the frequencies of the stimulation signal and the monitoring signal are similar, preferably differing by a factor of at most 5, more preferably by a factor of at most 2, more preferably by a factor of at most 1.1, in which case the stimulation signal is generated in such a way that it does not evoke any motor and / or sensory response, or in any case any significant one, i.e., is below the perceptual threshold.

[0011] In a further embodiment, the monitoring signal has a frequency of 0.1 Hz to 10 Hz, preferably 0.5 Hz to 5 Hz, more preferably 1 Hz to 2 Hz, and / or the stimulation signal has a frequency of at least 5 kHz, preferably at least 10 kHz, more preferably at least 20 kHz. The above-mentioned value ranges for the frequencies of the monitoring and stimulation signals have proven particularly advantageous. If a motor response is to be elicited (motor monitoring signal), the above value ranges for the frequency of the monitoring signal are particularly advantageous. If a sensory response / perception is to be elicited (sensory monitoring signal), the monitoring signal preferably has a frequency of 3 Hz to 5 Hz.

[0012] In a further embodiment, the stimulation signal has a frequency of 0.1 Hz to 200 Hz, preferably 0.5 Hz to 50 Hz, more preferably 3 Hz to 5 Hz, and in particular the stimulation signal has a signal strength below the perception threshold.

[0013] In a further embodiment, the monitoring signal has an amplitude of 0.01 mA to 20 mA, preferably 0.1 mA to 10 mA, more preferably 0.5 mA to 3 mA. The above-mentioned value ranges for the amplitude of the current magnitude of the monitoring signal have proven particularly advantageous. If a motor response is to be elicited (motor monitoring signal), the above value ranges for the amplitude of the monitoring signal are particularly advantageous. If a sensory response / perception is to be elicited (sensory monitoring signal), the monitoring signal preferably has an amplitude of 0.03 mA to 60 mA, preferably 0.3 mA to 30 mA, more preferably 1.5 mA to 9 mA.

[0014] In a further embodiment, the signal generator is configured to generate the monitoring signal as a pulsed signal and the stimulation signal as a pulsed signal, where the stimulation signal is generated at an amplitude below the perceptual threshold, i.e. so as not to evoke a motor and / or sensory response, or in any case any significant one.

[0015] In a further embodiment, the signal generator is configured to generate the monitoring signal as a pulsed signal and the stimulation signal as a continuous signal. The stimulation signal is preferably generated as a broadband and / or high-frequency signal. In this embodiment, a time-continuous emission of the stimulation signal is thus provided, whereas the monitoring signal is emitted in pulses and thus discontinuously or at otherwise discrete times. Such a continuous emission of the stimulation signal, on the one hand, and a pulsed emission of the monitoring signal, on the other hand, have proven particularly advantageous.

[0016] In a further embodiment, the monitoring signal has a pulse width of 0.01 ms to 20 ms, preferably 0.05 ms to 10 ms, more preferably 0.1 ms to 1 ms. The above-mentioned value ranges for the pulse width of the monitoring signal have particular advantages. If a motor response is to be elicited (motor monitoring signal), the above value range for the pulse width of the monitoring signal is particularly advantageous. If a sensory response / perception is to be elicited (sensory monitoring signal), the monitoring signal preferably has a pulse width of 0.2 ms.

[0017] In a further embodiment, the signal generator is configured to generate the monitoring signal in at least one burst having a pulse count of 1 to 100 pulses, preferably 1 to 10 pulses, and more preferably 1 to 5 pulses. In this embodiment, intermittent generation and emission of the monitoring signal is therefore provided. The generation and emission is in the form of at least one burst, i.e., a series of single pulses, each of which has a defined number of single pulses. The pulses preferably have the same pulse width, i.e., pulse duration. More preferably, a defined (short) pause is provided between each of the pulses. If multiple consecutive bursts are generated and emitted, a (longer) pause is provided between the bursts. In this embodiment of the invention, the generation and emission of the monitoring signal relative to the stimulation signal is time-dependently controlled. In this way, unwanted overlap of the physiological responses generated by the two signals can be prevented in an even more improved manner. In addition, it is not possible to prevent the monitoring signal, and the resulting motor and / or sensory responses, from inducing a certain level of discomfort in the patient under all circumstances. Such potentially unpleasant side effects of the monitoring signal for the patient can be reduced to a minimum by a time-limited / restricted signal emission in the form of at least one pulse and / or one burst.

[0018] In a further embodiment, the signal generator is configured to generate the monitoring signal in at least two consecutive bursts, with a rest period between the bursts of at least 10 seconds, preferably at least 15 seconds, and more preferably at least 20 seconds. Such a selection of the rest period avoids excessive strain on the patient due to the monitoring signal and the motor and / or sensory responses caused by it. This embodiment of the invention also arises from the consideration that monitoring the electrode distance does not necessarily have to be performed continuously over time. Monitoring at several time intervals will usually already be sufficient. This embodiment allows monitoring at such time intervals, with the time interval for distance monitoring being defined by the rest period between the bursts.

[0019] In a further embodiment, the signal generator is configured to generate alternating monitoring and stimulation signals, the electrodes being configured in this case for alternating or simultaneous emission of the two signals.

[0020] In a further embodiment, the signal generator is configured to generate the monitoring signal and the stimulation signal simultaneously, and in this embodiment, the electrodes are accordingly configured for simultaneous emission of the two signals.

[0021] The present invention also relates to a method for monitoring electrode distance during pain treatment by electrical nerve stimulation, the method comprising the steps of: generating an electrical monitoring signal, the monitoring signal being generated by a signal generator of a medical device; emitting the generated monitoring signal via electrodes of an invasive part of the medical device connected to the signal generator, the electrodes being positioned at a certain distance to a nerve, the monitoring signal acting on the nerve to induce a motor and / or sensory response, the form of which depends on the electrode distance; detecting the form of the motor and / or sensory response, the form of which is detected by a detection device of the medical device and / or by medical personnel; and monitoring the electrode distance in response to the detected form of the motor and / or sensory response. Advantages associated with the method of the present invention correspond to those of the medical device of the present invention. To avoid repetition, reference is made at this point to the disclosure of the medical device, which also applies mutatis mutandis to the method of the present invention. Further embodiments of the method of the present invention result from the features of the medical device of the present invention and its embodiments.

[0022] Further advantages and features of the invention result from the claims and from the following description of preferred exemplary embodiments of the invention, which are illustrated on the basis of the drawings. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a schematic block diagram of an embodiment of a medical device according to the present invention intended for use in treating pain; FIG. [Figure 2] 1 is a simplified schematic diagram illustrating the characteristics of electrical signals generated and emitted by a medical device. [Figure 3] 1 is a schematic block diagram of an embodiment of a method according to the present invention for monitoring electrode distance during pain treatment; DETAILED DESCRIPTION OF THE INVENTION

[0024] According to FIG. 1, a medical device 1 is intended for use in pain treatment and comprises a signal generator 2 , an invasive part 3 and electrodes 4 .

[0025] The signal generator 2 is configured to generate an electrical stimulation signal S and an electrical monitoring signal K. The electrodes 4 are configured to emit the stimulation signal S and the monitoring signal K. The signal generator 2 and the electrodes 4 are connected to each other by a signal line 5. The signal line 5 is used to transmit the generated signals S, K from the signal generator 2 to the electrodes 4. The signal line 5 can be a wired or wireless transmission line, with wired transmission being preferred.

[0026] The electrode 4 is arranged and / or formed at the distal end (not specified in more detail) of the invasive part 3. The invasive part 3 can be understood as an electrode 4, and vice versa. In other words, the invasive part 3 is optional and is not present in all embodiments. In the simplest case, the medical device only comprises a signal generator and an electrode, which can be designed, for example, in the form of a signal wire, which is elongated starting from the signal generator.

[0027] The invasive component 3, which includes the electrode 4, is configured to be introduced into the patient's body. The invasive component may be, for example, a catheter, a stimulation cannula, etc. In contrast, the signal generator 2 is an extracorporeal component of the medical device 1 and is therefore configured to remain outside the patient's body.

[0028] In use of the medical device 1, the electrode 4 is placed in the region of a nerve N. In the exemplary usage situation shown in Figure 1, the electrode 4 is placed at a distance G from the nerve N.

[0029] The stimulation signal S generated by the signal generator 2 and emitted by the electrode 4 is configured to inhibit the stimulation transmission E of the nerve N. Said inhibition H is shown diagrammatically in a highly simplified form in Figure 1 as a kind of blockage of the stimulation transmission E. The inhibition H of the stimulation transmission E results in a reduction or otherwise suppression of pain.

[0030] The monitoring signal K is configured to act on the nerve N to induce a motor response R. The form or otherwise the strength of the motor response depends on the distance G between the electrode 4 and the nerve N. This therefore applies to the effectiveness of pain relief by the stimulation signal S. An excessively strong reduction of the distance G may result in too much electrical energy being transmitted to the nerve N by the stimulation signal S. Conversely, an excessively strong increase of the distance G may result in too little electrical stimulation energy of the stimulation signal S. Both may result in a loss of effectiveness of the pain treatment.

[0031] The medical device 1 allows, in particular, monitoring of the distance G, in that a motor response R is detected and the distance G is adjusted accordingly. The detection of the motor response R can in the simplest case be performed by a medical professional, i.e., the user of the medical device 1. Based on the observed motor response R, and more precisely its morphology / strength, the user can decide whether the electrode 4 has to be moved relative to the nerve N to achieve an optimal therapeutic effect, in order to optimize the distance G and the inhibition H, which is dependent on the distance G. Alternatively or additionally, the therapeutic effect can be adapted by adaptation, in particular amplification, of the stimulation signal S.

[0032] In one embodiment not shown, the medical device includes a detection device configured for sensor-based detection of a motor response, particularly its morphology, and for generating a signal representative of the morphology of the detected motor response, such that the distance can be adjusted in response to the signal generated by the detection device.

[0033] However, there are also applications in which only sensory nerves are stimulated. In the case of purely sensory neuromodulation, monitoring by motor response is not possible. In this case, reference can instead be made to the sensory response and therefore to a "sensory monitoring signal." Position monitoring in this case is not based on a motor response, but rather on patient feedback regarding the sensory perception caused by the monitoring signal. The patient perceives the (sensory) monitoring signal and provides corresponding feedback to the attending anesthesiologist. If the patient does not perceive anything, the distance / intensity has been selected incorrectly. If the patient perceives the monitoring signal too strongly, the intensity is reduced / the distance is increased. The terms "sensory monitoring signal" and "motor monitoring signal" are summarized under the term "monitoring signal" within the scope of this disclosure, unless otherwise stated.

[0034] The stimulation signal S and the monitoring signal K have different characteristics, in particular different electrical and / or different signaling characteristics, which will be explained below with reference to FIG.

[0035] 2 shows, in a very simplified schematic manner, the time course of two signals S, K, in which the amplitude A is plotted with respect to time t. In this case, the amplitude A refers to the current magnitude of the respective signals S, K.

[0036] In the illustrated embodiment, the monitoring signal K is a low frequency signal having a frequency FK. The stimulus signal S is a high frequency signal having a frequency FS. The frequency FS is approximately 2.5×10 times higher than the frequency FK of the monitoring signal K in the illustrated embodiment. 3 In the present case, the frequency FK of the monitoring signal K is in particular 1 Hz. The frequency FS of the stimulus signal is in the present case 25 kHz.

[0037] In one embodiment not shown, the stimulation signal has a frequency of 0.1 Hz to 200 Hz, preferably 0.5 Hz to 50 Hz, more preferably 3 Hz to 5 Hz, and in particular the stimulation signal has a signal strength below the perception threshold.

[0038] Furthermore, the amplitude AK of the monitoring signal K is 1.5 mA in the present case. In an embodiment not shown, the amplitude of the monitoring signal is between 0.01 mA and 20 mA.

[0039] As further shown in Figure 2, the stimulation signal S is a continuous signal C. In contrast, the monitoring signal K is a pulsed signal P. In other words, the stimulation signal S is emitted continuously, or in any case quasi-continuously, with respect to time t. In contrast, the monitoring signal K is generated and emitted in a pulsed or otherwise periodic manner and / or with interruptions over time.

[0040] As shown in the enlarged area in Figure 2, the pulse width tP of the supervisory signal K is 0.5 ms in this case. In an embodiment not shown, the pulse width of the supervisory signal is between 0.01 ms and 20 ms.

[0041] As further shown in FIG. 2, the monitoring signal K is generated and emitted in multiple bursts, or in other words, intermittently, with multiple bursts B1, B2, and B3 shown here as examples. These may also be designated as a first burst B1, a second burst B2, and a third burst B3. It should be apparent that the number of bursts shown here is merely exemplary. Of course, depending on the duration of the pain treatment, more or even significantly more than the three bursts shown here as examples may be generated and emitted.

[0042] Each of the illustrated bursts B1, B2, and B3 includes a defined number of pulses Q, in this case four pulses emitted per burst. This number of pulses is also exemplary. In embodiments not shown, the number of pulses per burst is between 1 and 100 pulses, preferably between 1 and 10 pulses, and more preferably between 1 and 5 pulses.

[0043] Between each of the bursts B1, B2, B3 there is a pause time tR, which in this case is 20 seconds. In an embodiment not shown, the pause time is at least 10 seconds, preferably at least 15 seconds, more preferably at least 20 seconds.

[0044] FIG. 3 illustrates, in a schematic and simplified manner, a method 10 for monitoring the distance of an electrode 4 during use of a medical device 1. The method provides a step 11 of generating an electrical monitoring signal K, the monitoring signal K being generated by a signal generator 2. The method further provides a step 12 of emitting the generated monitoring signal K, the monitoring signal K being emitted via an electrode 4 of an invasive component 3, which is connected to the signal generator 2 by a signal line 5. The electrode 4 is now positioned at a distance G to the previously mentioned nerve N. The monitoring signal K acts on the nerve N to induce the previously mentioned motor and / or sensory response R, the form or otherwise strength of which depends on the distance G. The method further provides a step 13 of detecting the form of the motor and / or sensory response R. The detection 13 is performed either by the optional detection device described above or by the medical personnel themselves. Furthermore, the method 10 provides a step 14 of monitoring the distance G in response to the detected form of the motor and / or sensory response R. The monitoring 14 is performed by the medical personnel themselves in the simplest case. Alternatively, the medical device may include an optional monitoring device that automatically monitors and optionally adjusts the distance. This monitoring and optional adjustment may be in response to signals generated by the optional detection device and indicative of some form of motor and / or sensory response, for example.

[0045] In a further embodiment, the following ranges of values ​​have been found to be advantageous for the pulse width, frequency and current magnitude of the monitoring and stimulation signals:

[0046] [Table 1] [Explanation of symbols]

[0047] 1. Medical devices 2 Signal generator 3 Invasive parts 4 electrodes 5 Signal line

Claims

1. an invasive component (3) having at least one electrode (4) arranged on a nerve (N) and configured to emit an electrical stimulation signal (S); a signal generator (2) connected to the electrodes (4) and configured to generate the stimulation signal (S); Including, The stimulation signal (S) is configured to inhibit (H) the stimulation transmission (E) of the nerve (N). A medical device (1) for use in treating pain, The medical device (1) is characterized in that the at least one electrode (4) is configured to emit an electrical monitoring signal (K), the signal generator (2) is configured to generate the monitoring signal (K), the monitoring signal (K) is configured to induce a motor and / or sensory response (R), the form of which depends on the distance (G) between the electrode (4) and the nerve (N).

2. 2. The medical device (1) of claim 1, wherein the electrical stimulation signal (S) is not configured to induce a motor and / or sensory response, and the electrical monitoring signal (K) is not configured to inhibit the stimulation transmission (E) of the nerve (N).

3. The frequency (FS) of the stimulus signal (S) is at least 0.5×10 higher than the frequency (FK) of the monitoring signal (K). ３ , preferably at least 1.0×10 ３ , more preferably 1.5 × 10 ３ 3. The medical device (1) according to claim 1 or 2, wherein the medical device (1) is twice as large.

4. 3. The medical device (1) according to claim 1 or 2, wherein the frequency (FS) of the stimulation signal (S) and the frequency (FK) of the monitoring signal (K) are similar.

5. 5. Medical device (1) according to any one of claims 1 to 4, wherein the monitoring signal (K) has a frequency (FK) of 0.1 Hz to 10 Hz, preferably 0.5 Hz to 5 Hz, more preferably 1 Hz to 2 Hz, and / or the stimulation signal (S) has a frequency (FS) of at least 5 kHz, preferably at least 10 kHz, more preferably at least 20 kHz.

6. 5. The medical device (1) according to any one of claims 1 to 4, wherein the stimulation signal (S) has a frequency (FK) of 0.1 Hz to 200 Hz, preferably 0.5 Hz to 50 Hz, more preferably 3 Hz to 5 Hz, in particular the stimulation signal (S) has a signal strength below the perception threshold.

7. 7. Medical device (1) according to any one of claims 1 to 6, wherein the monitoring signal (K) has an amplitude (AK) of 0.01 mA to 20 mA, preferably 0.1 mA to 10 mA, more preferably 0.5 mA to 3 mA.

8. 8. The medical device (1) according to any one of claims 1 to 7, wherein the signal generator (2) is configured to generate the monitoring signal (K) as a pulse signal (P) and to generate the stimulation signal (S) as a pulse signal (P).

9. 9. The medical device (1) according to any one of claims 1 to 8, wherein the signal generator (2) is configured to generate the monitoring signal (K) as a pulsed signal (P) and the stimulation signal (S) as a continuous signal (C).

10. 10. Medical device (1) according to claim 9, wherein the monitoring signal (K) has a pulse width (tP) of 0.01 ms to 20 ms, preferably 0.05 ms to 10 ms, more preferably 0.1 ms to 1 ms.

11. 11. The medical device (1) according to claim 9 or 10, wherein the signal generator (2) is configured to generate the monitoring signal (K) in at least one burst (B1, B2, B3) having a number of pulses between 1 and 100 pulses, preferably between 1 and 10 pulses, more preferably between 1 and 5 pulses.

12. 12. The medical device (1) according to claim 11, wherein the signal generator (2) is configured to generate the monitoring signal (K) in at least two consecutive bursts (B1, B2, B2, B3), the rest time (tR) between the bursts (B1, B2, B2, B3) being at least 10 seconds, preferably at least 15 seconds, more preferably at least 20 seconds.

13. 13. The medical device (1) according to any one of claims 1 to 12, wherein the signal generator (2) is configured to alternately generate the monitoring signal (K) and the stimulation signal (S).

14. 13. The medical device (1) according to any one of claims 1 to 12, wherein the signal generator (2) is configured to generate the monitoring signal (K) and the stimulation signal (S) simultaneously.

15. A method (10) for electrode (4) distance monitoring during pain treatment by electrical nerve stimulation, comprising: generating (11) an electrical monitoring signal (K), said monitoring signal (K) being generated by a signal generator (2) of the medical device (1); a step (12) of emitting the generated monitoring signal (K), wherein the monitoring signal (K) is emitted via an electrode (4) of an invasive part (3) of the medical device (1) connected to the signal generator (2), the electrode (4) being positioned at a certain distance (G) to a nerve (N), the monitoring signal (K) acting on the nerve (N) to induce a motor and / or sensory response (R), the form of which response (R) depends on the distance (G); detecting (13) a form of said motor and / or sensory response (R), said motor and / or sensory response (R) being detected by a detection device of said medical device and / or by medical personnel; monitoring (14) the distance (G) of the electrodes (4) in response to the form of the detected motor and / or sensory response (R); A method comprising:

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