Medical device for use in the treatment of pain

Abstract

A medical device for use in the treatment of pain. 2.1 A medical device is known comprising an invasive component having at least one electrode configured to be positioned at a nerve and to emit an electrical stimulation signal, and a signal generator connected to the electrode and configured to generate a stimulation signal wherein the stimulation signal is configured to inhibit stimulation delivery of the nerve. 2.2 according to the invention, the at least one electrode is configured to emit an electrical monitoring signal and the signal generator is configured to generate a monitoring signal wherein the monitoring signal is configured to trigger a motor and / or sensory response, the form of which depends on the distance between the electrode and the nerve. 2.3 for the treatment of pain by means of nerve stimulation.

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 and a signal generator, the at least one electrode being configured to be positioned at a nerve and to emit an electrical stimulation signal, the signal generator being connected to the electrode and configured to generate a stimulation signal, wherein the stimulation signal is configured to inhibit nerve stimulation transmission. Background Technology

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

[0003] The position of the electrodes relative to the nerve to be stimulated is crucial for the achievable therapeutic effect. If the electrodes are moved closer to the nerve during the stimulation procedure, the stimulation energy emitted at the nerve increases. If the electrodes are moved further away, the stimulation energy acting on the nerve in this manner decreases. Such changes in distance and accompanying changes in stimulation energy can be caused, for example, by patient movement.

[0004] Methods for adjusting the emitted stimulation energy are known from the prior art. These methods provide for the tracking and correction of stimulation energy and are used within the field of nerve stimulation (SCS) in the spinal canal. For this purpose, for example, the “connection” of the stimulation signal at the nerve and the nerve’s response are measured. The stimulation energy of the electrical stimulation signal is then adjusted accordingly.

[0005] The nerve response can only be measured when two electrodes are in direct contact with the nerve. When stimulating peripheral nerves in the so-called single-shot technique, continuous contact between one or more electrodes and the nerve cannot be assumed. Summary of the Invention

[0006] The object of this invention is to provide a medical device of the type mentioned at the beginning, which is capable of achieving improved pain management.

[0007] This objective is achieved by configuring at least one electrode to emit an electrical monitoring signal and a signal generator to generate the monitoring signal, wherein the monitoring signal is configured to generate a motor and / or sensory response, the form of which depends on the distance between the electrode and the nerve. Thus, the medical device according to the invention allows the generation and emission of two signals: an electrical stimulation signal on the one hand and an electrical monitoring signal on the other. The stimulation signal is used for actual pain suppression because it inhibits the transmission of stimulation to the affected nerve. The monitoring signal is used to monitor the position or distance of the electrode because it is configured to trigger a motor and / or sensory response in the patient, the form of which depends on the distance between the electrode and the nerve. Based on the form of the motor and / or sensory response, the medical personnel performing pain treatment (through the patient's own feedback in the case of a sensory response) can identify whether the electrode must be repositioned to achieve optimal pain treatment. In the case of insignificant motor and / or sensory responses, further distal advancement of the electrode in the direction of the nerve is generally necessary. In the case of strong or excessively strong motor and / or sensory responses, proximal retraction of the electrode to increase the distance is generally necessary. The form of the motor and / or sensory response may also depend on the intensity of the monitoring signal. In cases of strong or excessively strong motor and / or sensory responses, it may be necessary to adjust (especially reduce) the intensity of the overall signal, which consists of a stimulation signal and a monitoring signal. Electrical stimulation signals used for actual pain suppression have specific properties, particularly electrical properties and / or signal transmission properties. These properties are known to those skilled in the art, and therefore need not be explicitly described herein. Electrical monitoring signals have different properties, particularly different electrical properties and / or different signal transmission properties. In one embodiment, the invasive component is a catheter to which the at least one electrode is attached. In another embodiment, the invasive component is a stimulation cannula to which the at least one electrode is attached. In yet another embodiment, the invasive component is a wire and may form the 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 another embodiment, at least two electrodes are present, wherein the first of the two electrodes is configured to emit a stimulation signal and the second of the two electrodes is configured to emit a monitoring signal. Alternatively or additionally, the first of the at least two electrodes may serve as a cathode, and the second of the at least two electrodes may serve as an anode. An invasive component, including electrodes, is configured to be introduced into the patient's body. In contrast, a signal generator is an external component of the medical device, which is wired to the 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, and in particular, the form of, motor and / or sensory responses triggered by a monitoring signal.Furthermore, in another embodiment, such a detection device is configured to generate a signal based on the form of the detected motor and / or sensory response, the signal representing the form of the motor and / or sensory response. The signal is preferably an acoustic or optical signal and / or a signal that can be perceived in another way by a medical professional, and based on this signal, the medical professional can decrease or increase the distance between the electrodes and the nerve. In another embodiment, such a detection device is not provided. Instead, the form of the motor and / or sensory response is detected by the medical professional themselves, for example, visually or tactilely and / or in another way.

[0008] In one embodiment, the electrical stimulation signal is configured such that it does not trigger (particularly, does not trigger substantially significant) motor and / or sensory responses, and the monitoring signal is configured such that it does not generate inhibition of stimulus transmission. In other words, in this embodiment, there is no, or in any case, substantially no, overlap in the (multiple) physiological responses generated by the relevant signals. In this embodiment, the stimulation signal has at most a minor effect on motor and / or sensory responses, preferably no effect. This prevents the monitoring signal from superimposing on the effect of the stimulation signal and thus impairing its effect in an undesirable manner. Conversely, it also prevents the stimulation signal from impairing and disrupting the effect of the monitoring signal.

[0009] In another embodiment, the stimulation signal has a frequency that is at least 0.5 × 10⁻⁶ times that of the monitoring signal. 3 Times, preferably at least 1×10 3 More preferably 1.5 × 10 3 In this embodiment, the stimulus signal is high-frequency relative to the monitoring signal. Conversely, the monitoring signal is low-frequency relative to the stimulus signal. This frequency selection prevents undesirable overlap in physiological effects (on the one hand, inhibiting stimulus transmission, and on the other hand, triggering motor and / or sensory responses).

[0010] In another embodiment, the frequencies of the stimulus signal and the monitoring signal are similar. Preferably, the frequencies differ by at most a factor of 5, more preferably at most a factor of 2, and even more preferably at most a factor of 1.1. In this case, the stimulus signal is generated such that it does not trigger, or in any case does not trigger, a substantially significant motor and / or sensory response, i.e., below the perception threshold.

[0011] In another 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 ranges of frequencies for the monitoring and stimulation signals have been found to be particularly advantageous. The above-mentioned ranges of frequencies for the monitoring signal are particularly advantageous when a motor response (motor monitoring signal) is to be triggered. If a sensory response / perception (sensory monitoring signal) is to be triggered, the monitoring signal preferably has a frequency of 3 Hz to 5 Hz.

[0012] In another 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 particularly wherein the stimulation signal has a signal strength below the perception threshold.

[0013] In another embodiment, the monitoring signal has an amplitude of 0.01 mA to 20 mA, preferably 0.1 mA to 10 mA, and more preferably 0.5 mA to 3 mA. The above-mentioned range of amplitude values ​​for the ampere number of the monitoring signal has been found to be particularly advantageous. This range of amplitude values ​​for the monitoring signal is particularly advantageous when triggering a motion response (motion monitoring signal). If triggering a sensory response / perception (sensory monitoring signal) is desired, the monitoring signal preferably has an amplitude of 0.03 mA to 60 mA, preferably 0.3 mA to 30 mA, and more preferably 1.5 mA to 9 mA.

[0014] In another embodiment, the signal generator is configured to generate a monitoring signal as a pulse signal and a stimulus signal as a pulse signal. In this case, the stimulus signal is generated with an amplitude below the perception threshold, i.e., such that it does not trigger, or in any case, a substantially significant motor and / or sensory response.

[0015] In another embodiment, the signal generator is configured to generate a monitoring signal as a pulsed signal and a stimulus signal as a continuous signal. The stimulus signal is preferably generated as a broadband and / or high-frequency signal. In this embodiment, the stimulus signal is thus provided for continuous temporal transmission, while the monitoring signal is transmitted in a pulsed and therefore discontinuous manner, or at discrete times. It has been found that such continuous transmission of the stimulus signal on the one hand and pulsed transmission of the monitoring signal on the other is particularly advantageous.

[0016] In another embodiment, the monitoring signal has a pulse width of 0.01 ms to 20 ms, preferably 0.05 ms to 10 ms, and more preferably 0.1 ms to 1 ms. The above-mentioned range of pulse width values ​​for the monitoring signal has particular advantages. This range is especially advantageous when triggering a motion response (motion monitoring signal). If triggering a sensory response / perception (sensory monitoring signal) is desired, the monitoring signal preferably has a pulse width of 0.2 ms.

[0017] In another embodiment, the signal generator is configured to generate a monitoring signal with at least one burst of pulses, the burst having a pulse count of 1 to 100 pulses, preferably 1 to 10 pulses, and more preferably 1 to 5 pulses. Thus, in this embodiment, intermittent generation and emission of the monitoring signal are provided. Generation and emission occur in the form of at least one burst of pulses (i.e., a sequence of single pulses, wherein the sequence has a defined number of single pulses). The pulses preferably each have the same pulse width, i.e., pulse duration. More preferably, a defined (short) pause duration is provided between each of the pulses. If multiple consecutive bursts are generated and emitted, a (longer) pause duration is provided between the bursts. In this embodiment of the invention, the generation and emission of the monitoring signal associated with the stimulus signal occur in a very restricted manner in terms of temporal sequence. In this way, it is possible to prevent the undesirable superposition of physiological responses generated by two signals in a further improved manner. Furthermore, it is impossible to exclude, in all cases, the monitoring signal and the motor and / or sensory responses triggered by it from causing some discomfort in the patient. By transmitting signals in a time-restricted / constrained manner in the form of at least one pulse and / or a burst pulse, the potential unpleasant side effects of monitoring signals on patients can be minimized.

[0018] In another embodiment, the signal generator is configured to generate a monitoring signal with at least two consecutive burst pulses, wherein the pulse duration between the burst pulses is at least 10 seconds, preferably at least 15 seconds, and more preferably at least 20 seconds. This selection of the pause duration avoids excessive fatigue in the patient caused by the monitoring signal and by motor and / or sensory responses triggered by the monitoring signal. Furthermore, this embodiment of the invention is based on the consideration that the monitoring of electrode distance does not necessarily have to occur in a time-continuous manner. Monitoring at regular time intervals is often sufficient. This embodiment allows monitoring at such time intervals, wherein the time interval for monitoring distance is defined by the pause duration between the burst pulses.

[0019] In another embodiment, the signal generator is configured to alternately generate monitoring and stimulation signals. In this case, the electrodes are configured to emit the two signals alternately or simultaneously.

[0020] In another embodiment, the signal generator is configured to simultaneously generate a monitoring signal and a stimulation signal. In this embodiment, the electrodes are also correspondingly configured to emit both signals simultaneously.

[0021] The present invention also relates to a method for monitoring the distance of electrodes during pain treatment by means of electrical nerve stimulation. The method according to the invention includes the following steps: generating an electrical monitoring signal, wherein the monitoring signal is generated by means of a signal generator of a medical device; transmitting the generated monitoring signal, wherein the monitoring signal is transmitted via electrodes connected to the signal generator via an invasive component of the medical device, wherein the electrodes are positioned at a distance from the nerve, and wherein the monitoring signal triggers a motor and / or sensory response by acting on the nerve, the form of which depends on the distance of the electrodes; detecting the form of the motor and / or sensory response, wherein the form of the motor and / or sensory response is detected by means of a detection device of the medical device and / or by a medical professional; and monitoring the distance of the electrodes based on the detected form of the motor and / or sensory response. The advantages of the method according to the invention correspond to the advantages of the medical device according to the invention. To avoid repetition, reference is made in this regard to the disclosure of the medical device, which, with necessary modifications, is also applicable to the method according to the invention. Further embodiments of the method according to the invention are derived from the features of the medical device and its embodiments according to the invention. Attached Figure Description

[0022] Further advantages and features of the invention will become apparent from the claims and the following description of preferred exemplary embodiments of the invention illustrated in the accompanying drawings.

[0023] Figure 1 A schematic block diagram of an embodiment of a medical device according to the invention intended for use in pain management is shown.

[0024] Figure 2 A simplified schematic diagram is shown to illustrate the nature of electrical signals generated and emitted by means of a medical device, and

[0025] Figure 3 A schematic block diagram of an embodiment of a method according to the invention for monitoring the distance of electrodes during pain treatment is shown. Detailed Implementation

[0026] according to Figure 1 The medical device 1 is intended for use in pain management and includes a signal generator 2, an invasive component 3, and an electrode 4.

[0027] Signal generator 2 is configured to generate an electrical stimulation signal S and an electrical monitoring signal K. Electrode 4 is configured to emit the stimulation signal S and the monitoring signal K. Signal generator 2 and electrode 4 are connected to each other by means of signal line 5. Signal line 5 is used to transmit the generated signals S and K from signal generator 2 to electrode 4. Signal line 5 can be a wired or wireless transmission line, wherein wired transmission is preferred.

[0028] Electrode 4 is arranged and / or formed at the distal end (not specified in more detail) of invasive component 3. Invasive component 3 can be understood as electrode 4, and vice versa. In other words, invasive component 3 is optional and not present in all embodiments. In the simplest case, the medical device includes only a signal generator and an electrode, which may be designed, for example, as a signal wire extending from the signal generator.

[0029] The invasive component 3, including 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 external component of the medical device 1 and is therefore configured to remain outside the patient's body.

[0030] In the use of medical device 1, electrode 4 is positioned in the region of nerve N. Figure 1 In the exemplary use case shown, electrode 4 is positioned at a distance G from nerve N.

[0031] A stimulation signal S, generated by signal generator 2 and emitted by electrode 4, is configured to inhibit the stimulation transmission E of nerve N. This inhibition occurs in… Figure 1 The diagram illustrates, in a very simplified form, the types of interruption of stimulus transmission E. Inhibition of stimulus transmission E leads to pain relief or suppression.

[0032] The monitoring signal K is configured to trigger a motor response R by acting on the nerve N. The form or intensity of the motor response depends on the distance G between the electrode 4 and the nerve N. This correspondingly applies to the effectiveness of pain relief by means of the stimulation signal S. An excessively strong decrease in distance G may result in excessive electrical energy being transmitted to the nerve N via the stimulation signal S. Conversely, an excessively strong increase in distance G may result in excessively low electrical stimulation energy of the stimulation signal S. Both can lead to impaired effectiveness of pain treatment.

[0033] Medical device 1 allows for the monitoring of distance G, particularly because the motor response R is detected and distance G is adjusted accordingly. In its simplest case, the detection of the motor response R can be performed by a medical professional (i.e., the user of medical device 1). Based on the observed motor response R (more precisely, its form / intensity), the user can determine whether electrode 4 must be moved relative to nerve N to achieve optimal therapeutic effect, in order to optimize distance G and the inhibition H dependent on distance G. Alternatively or additionally, the therapeutic effect can be tuned (particularly amplified) by adjusting the stimulation signal S.

[0034] In an embodiment not shown in the accompanying drawings, the medical device includes a detection device configured for sensor-based detection of motion responses, particularly their forms, and for generating a signal representing the form of the detected motion response. The distance can be adjusted accordingly based on the signal generated by means of the detection device.

[0035] However, there are also applications that only stimulate sensory nerves. In cases of neuromodulation of sensory nerves alone, monitoring via motor responses cannot occur. In such cases, sensory responses are referenced instead, and accordingly, "sensory monitoring signals" are referenced. Position monitoring in this case is not based on motor responses, but rather on patient feedback regarding sensory perception elicited 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 incorrectly selected. If the patient perceives the monitoring signal excessively, the intensity is reduced / the distance is increased. The terms "sensory monitoring signal" and "motor monitoring signal" are encompassed within the scope of this disclosure under the term "monitoring signal" unless otherwise described.

[0036] The stimulus signal S and the monitoring signal K have different properties, particularly different electrical properties and / or different signal transmission properties. (Referring to...) Figure 2 Explain these different properties.

[0037] Figure 2 A very simplified time process for two signals S and K is schematically illustrated, where the amplitude A, as shown in the figure, varies with time t. In the present case, amplitude A refers to the ampere number of the corresponding signals S and K.

[0038] In the illustrated embodiment, the monitoring signal K is a low-frequency signal with frequency FK. The stimulation signal S is a high-frequency signal with frequency FS. In the illustrated embodiment, frequency FS is approximately 2.5 × 10⁻⁶ times the frequency FK of the monitoring signal K. 3 The frequency FK of the monitoring signal K is 1 Hz. The frequency FS of the stimulus signal is 25 kHz.

[0039] In embodiments not shown in the figures, 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 particularly wherein the stimulation signal has a signal strength below the perception threshold.

[0040] Furthermore, under the current conditions, the amplitude AK of the monitoring signal K is 1.5 mA. In an embodiment not shown in the figure, the amplitude of the monitoring signal is between 0.01 mA and 20 mA.

[0041] like Figure 2 As further illustrated, the stimulus signal S is a continuous signal C. In contrast, the monitoring signal K is a pulse signal P. In other words, the stimulus signal S is emitted continuously or, in any case, quasi-continuously over time t. In contrast, the monitoring signal K is generated and emitted in a pulsed or cyclic manner and / or in a manner that provides time interruptions.

[0042] As in Figure 2 As shown in the magnified region, in the current case, the pulse width tP of the monitoring signal K is 0.5 ms. In embodiments not shown in the figure, the pulse width of the monitoring signal ranges from 0.01 ms to 20 ms.

[0043] like Figure 2 As further shown, the monitoring signal K is generated and emitted intermittently as multiple burst pulses, or in other words, burst pulses, wherein, in the current case, multiple burst pulses B1, B2, and B3 are shown by way of example. These can also be designated as the first burst pulse B1, the second burst pulse B2, and the third burst pulse B3. Obviously, the number of burst pulses shown is merely an example. Of course, depending on the duration of pain treatment, more or even significantly more burst pulses than the three shown as an example in the current case can be generated and emitted.

[0044] Each of the burst pulses B1, B2, and B3 shown includes a defined number of pulses Q, wherein, in the present case, four pulses are emitted for each burst pulse. This number of pulses is also exemplary. In embodiments not shown in the figures, the number of pulses in each burst pulse is 1 to 100 pulses, preferably 1 to 10 pulses, and more preferably 1 to 5 pulses.

[0045] A pause duration tR is provided between each of the burst pulses B1, B2, and B3. In the current case, this is 20 seconds. In an embodiment not shown in the figure, the pause duration is at least 10 seconds, preferably at least 15 seconds, and more preferably at least 20 seconds.

[0046] Figure 3A method 10 for monitoring the distance of electrode 4 during use of medical device 1 is illustrated in a simplified schematic manner. The method provides the generation 11 of an electrical monitoring signal K, wherein the monitoring signal K is generated by means of a signal generator 2. Furthermore, the method provides the transmission 12 of the generated monitoring signal K, wherein the monitoring signal K is transmitted via electrode 4 of the invasive component 3, which is connected to the signal generator 2 by means of a signal line 5. Electrode 4 is here positioned at the previously mentioned distance G to nerve N. The monitoring signal K triggers the previously mentioned motor and / or sensory response R by acting on nerve N, the form or intensity of which depends on distance G. Furthermore, the method provides the detection 13 of the form of the motor and / or sensory response R. Detection 13 is performed by means of the optional detection device described above or by a medical professional. Furthermore, method 10 provides the monitoring 14 of distance G based on the form of the detected motor and / or sensory response R. In the simplest case, monitoring 14 is performed by a medical professional. Alternatively, the medical device may include an optional monitoring device that automatically monitors and optionally adjusts the distance. Such monitoring and optional adjustments may occur, for example, based on signals generated by means of optional detection devices, and these signals represent the form of motor and / or sensory responses.

[0047] In another embodiment, the following value ranges have been found to be advantageous for the pulse width, frequency, and ampere number of the monitoring and stimulation signals:

[0048]

[0049]

Claims

1. A medical device (1) for use in pain treatment, comprising: An invasive component (3) having at least one electrode (4) configured to be positioned at a nerve (N) and to emit an electrical stimulation signal (S), and A signal generator (2), which is connected to the electrode (4) and configured to generate a stimulation signal (S), The stimulation signal (S) is configured to inhibit (H) the stimulation transmission (E) of the nerve (N). The feature is that the at least one electrode (4) is configured to emit an electrical monitoring signal (K), and the signal generator (2) is configured to generate the monitoring signal (K), wherein the monitoring signal (K) is configured to trigger 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. The medical device (1) according to claim 1, wherein, The electrical stimulation signal (S) is not configured to trigger motor and / or sensory responses, and the electrical monitoring signal (K) is not configured to inhibit the stimulation transmission (E) of the nerve (N).

3. The medical device (1) according to claim 1 or 2, wherein, The frequency (FS) of the stimulation signal (S) is at least 0.5 × 10⁻⁶ times the frequency (FK) of the monitoring signal (K). 3 Times, preferably 1.0 × 10 3 More preferably 1.5 × 10 3 times.

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

5. The medical device (1) according to any one of the preceding claims, 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 wherein, The stimulation signal (S) has a frequency (FS) of at least 5 kHz, preferably at least 10 kHz, and more preferably at least 20 kHz.

6. 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, and particularly wherein the stimulation signal (S) has a signal strength below the perception threshold.

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

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

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

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

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

12. The medical device (1) according to claim 11, wherein, The signal generator (2) is configured to generate the monitoring signal (K) with at least two consecutive burst pulses (B1, B2; B2, B3), wherein the pause duration (tR) between the burst pulses (B1, B2; B2, B3) is at least 10 s, preferably at least 15 s, and more preferably at least 20 s.

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

14. 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 monitoring the distance of an electrode (4) during pain treatment by means of electrical nerve stimulation, comprising the following steps: An electrical monitoring signal (K) is generated (11), wherein the monitoring signal (K) is generated by means of a signal generator (2) of a medical device (1); The monitoring signal (K) generated by the emission (12) is emitted via an electrode (4) of the invasive component (3) of the medical device (1) connected to the signal generator (2), wherein the electrode (4) is arranged at a distance (G) from the nerve (N), and wherein the monitoring signal (K) triggers a motor and / or sensory response (R) by acting on the nerve (N), the form of which depends on the distance (G); Detect (13) the form of the motor and / or sensory response (R), wherein the motor and / or sensory response (R) is detected by means of the detection device of the medical device and / or by medical personnel; The distance (G) of the electrode (4) is monitored (14) in the form of the detected motion and / or sensory response (R).

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