DEVICE FOR INTRAOPERATIVE NEUROMONITORING OF NERVES IN THE PELVIS OF A PATIENT

Description

[0001] The invention relates to a device for the intraoperative neuromonitoring of nerves in the pelvic region of a patient, comprising at least one nerve stimulator that can be introduced into the surgical area during an operation and at least one sensor device that can be connected to a pelvic organ of the patient.

[0002] A very delicate nerve network runs through the human pelvic area, containing motor, sensory, and autonomic nerve fibers. The risk of damage to this nerve network is very high during pelvic surgery (e.g., on the rectum, bladder, prostate, or uterus), and can severely limit the quality of life of affected patients.

[0003] The consequences of pelvic nerve damage are postoperative dysfunction of the pelvic organs. Up to 38% of patients suffer from urinary incontinence after pelvic surgery, approximately 46% from fecal incontinence, and 18-76% from sexual dysfunction. These significant limitations in quality of life affect a significant number of patients, given the high number of surgeries performed each year (according to the Federal Statistical Office, approximately 437,200 operations on the rectum, bladder, urethra, and internal genital organs in 2015).

[0004] The nerve network of the pelvis is highly complex, its structure is extremely fine and the position of the many different nerves varies from individual to individual. The established methods of neuromonitoring, as known from thyroid surgery, for example, cannot simply be transferred to use in the pelvic region. In particular, in rectal operations, efforts have been made for several years to use nerve-sparing surgical techniques, however, no system for standardized and routine intraoperative nerve monitoring in the pelvic region has yet been widely established. For the surgeon, distinguishing the nerves from the surrounding tissue and thus sparing the pelvic nerves is very difficult and requires in-depth knowledge of neuroanatomy and neurophysiology. The variation in the extent of the sheath fascia and fatty tissue in the pelvic cavity from patient to patient, as well as any additional tissue, also plays a role in the pelvic nerve system.Tumor infiltration also prevents the identification of the pelvic nerves.

[0005] EP 2 589 410 B1 discloses a generic device for the essentially simultaneous control of the stimulability of functions in the pelvic region controlled by the autonomic nervous system. The device comprises at least one stimulation electrode for intraoperative insertion into the pelvic cavity during an operation, and the sensor device comprises at least one sensor for measuring bladder pressure and at least one sensor for measuring the activity of the internal anal sphincter, the sensor for measuring the activity of the sphincter being an EMG sensor. The use of a pressure sensor to detect a response signal when the bladder is enervated by means of the stimulation electrode has proven disadvantageous, because this method requires at least partial filling of the bladder with fluid, which is inherently undesirable during surgery.The use of a pressure sensor on / in the bladder generally extends the operating time considerably. This is because, before checking the integrity of the nerve plexus, a large amount of fluid (Ringer's solution or similar) must first be introduced into the bladder via a urinary catheter placed prior to the operation. This fluid must then be drained again after the nerve(s) have been checked. Intraoperative EMG measurements of the anal sphincter have also not yet been widely accepted and established in clinical routine, as the values ​​obtained have proven too nonspecific, thus lacking the desired reliability. The main reason for this is that a large proportion of autonomic fibers exist in the nerve plexus in the pelvic region, the target muscle of which is smooth muscle. Smooth muscles contain pacemaker cells (Cajal cells), which control the activity of the smooth muscle and are modulated by autonomic fibers.The contraction of smooth muscle is therefore difficult to detect using a conventional EMG.

[0006] A device for measuring the volume, pressure or activity of the urinary bladder by means of impedance measurement is known from US 2013 / 079841.

[0007] The object of the invention is to create a device of the type mentioned above, with which it is possible to reliably and without significant delay check the integrity / functionality of nerves acting on one or more pelvic organ(s), in particular the bladder and / or the rectum, during an operation in the pelvic region of a patient. This object is achieved with the invention in that the sensor device has at least two measuring electrodes that can be applied to the pelvic organ, as well as an impedance measuring device connected or connectable to the measuring electrodes, with a display that indicates impedance changes in the pelvic organ between the measuring electrodes. The wording "applicable to the pelvic organ" is intended to encompass not only direct application, but also indirect, i.e.an application to a part of the body connected to the pelvic organ, such as the urethra, which forms the exit from the bladder.

[0008] It has surprisingly been shown that stimulating nerves connected to a pelvic organ such as the bladder or rectum leads to changes in the complex electrical resistance (impedance) of the affected organ tissue. These changes can serve as an indicator of the integrity of a nerve stimulated by the nerve stimulator. The invention makes it possible to measure the resulting impedance changes and display them on the display to the surgeon, thus providing feedback on whether the stimulated nerve is still fully functional, i.e., intact, or possibly injured during the operation.

[0009] The nerve stimulator is preferably a stimulation electrode, preferably bipolar, capable of being subjected to a stimulation current, which makes it easy to subject the autonomic and somatic pelvic nerves to direct electrical stimulation. This allows reproducible, stimulation-induced contractions in the pelvic organs to be triggered simply and reliably. The contraction of the smooth muscles of the bladder and rectum can be measured using the invention by measuring the change in tissue impedance. A particularly advantageous feature of the method implemented with the invention is that the measurement of the change in impedance in the bladder is possible even when it is empty, i.e., when it contains no fluid.The invention therefore makes it possible to carry out intraoperative localisation and functional control of the pelvic nerve plexus connected to the monitored pelvic organs, without the need for time-consuming preparation of the nerve plexus for carrying out a test stimulation, for example by filling it with Ringer's solution or the like.

[0010] The sensor device comprises a test current supply device with at least two test current electrodes that can be applied to the pelvic organ. The arrangement can be expediently configured, for example, so that one test current electrode and one measuring electrode are combined in one electrode unit. With such an arrangement, the measurement technique for impedance measurement using the four-electrode technique can be implemented particularly advantageously. A known constant current is preferably impressed as the test current into the body at the relevant pelvic organ via the two test current electrodes. The voltage across the measurement section generated by the tissue impedance is tapped via the two measuring electrodes. Changes in tissue impedance due to stimulation of a nerve connected to the organ lead to a change in the voltage tapped by the measuring electrodes, which is visible on the display device.

[0011] The constant current applied for measurements on the pelvic organ (bladder, rectum) (hereinafter referred to as the test current) should not contain any direct current components, as electrolysis between the electrodes can occur due to the fluids in the tissue when direct current is applied. The applied constant test current is therefore preferably modulated at a specific frequency, for example, a frequency of 50 kHz. For this purpose, in an advantageous development of the invention, the test current supply device provides an alternating test current applied to the test current electrodes with a fixed or adjustable test current frequency.

[0012] In order to be able to monitor impedance changes in various organs during an operation, the test current supply device can comprise several, in particular two, test current electrode pairs, each with two test current electrodes, as well as means for generating alternating test currents with different test current frequencies at the different test current electrode pairs. The different test current electrode pairs can then be applied to different organs, for example the bladder on the one hand and the rectum of the patient to be operated on, at suitable positions in order to apply a first test current with a first test current frequency to one organ and a second test current with a second frequency, different from the first test current frequency, to the other organ. In this way, the voltages tapped from the two organs using measuring electrodes can be clearly assigned to the organ in question.

[0013] The sensor device preferably has a measurement signal amplifier, preferably a lock-in amplifier, particularly preferably a dual-phase lock-in amplifier, which processes the measurement signal that can be tapped by means of the measuring electrodes.

[0014] It has proven particularly advantageous if the impedance measuring device consists essentially of an impedance spectroscope. Impedances consist of a real part and an imaginary part, with the real part corresponding to a purely ohmic resistance. The imaginary part is determined by capacitive and inductive components and is frequency-dependent. Contraction of the smooth muscle of the monitored pelvic organs can cause not only changes in the ohmic resistance between the measuring electrodes but also changes in the capacitive component of the impedance, which can be detected particularly clearly using an impedance spectroscope. In impedance spectroscopy, the modulation frequency of the test current is varied across a specific, defined frequency spectrum. This allows tissue impedance to be determined as a function of the modulation frequency. Impedance changes can thus be detected very reliably and clearly.

[0015] For particularly simple and reliable application of the electrodes to the pelvic organ to be monitored, it has proven advantageous if at least one electrode unit comprising a measuring electrode and a test current electrode is designed in the form of an electrode catheter and / or a rectal probe. An electrode catheter designed according to the invention can be inserted through the urethra in such a way that the two electrodes provided on it remain in reliable, direct contact with the bladder sphincter throughout the operation. Accordingly, the electrodes of a rectal probe designed according to the invention, which are intended for monitoring the rectum, rest on the anal sphincter when the probe has been inserted into the patient as intended.The other measuring and test current electrodes can be intramurally applied needle electrodes, which can be arranged, for example, as a pair of needles on a common needle electrode holder. Using such a holder, the surgeon can then insert them at a suitable location on the respective pelvic organ, remote from the electrode pair on the catheter or rectal probe.

[0016] As already indicated above, the sensor device preferably has at least two measuring electrodes and two test electrodes for application to the bladder and rectum of the patient.

[0017] Further features and advantages of the invention will become apparent from the following description and the drawing, which illustrates a preferred embodiment of the invention in more detail by way of example. It shows: Fig. 1 shows a device according to the invention in a schematic overview; and Fig. 2 shows an exemplary graphic representation of the response signal obtained upon stimulation of a pelvic nerve during impedance measurement at a pelvic organ.

[0018] In the Fig.1 A device for the intraoperative neuromonitoring of nerves in a patient's pelvic region, designated as a whole by 10, is schematically shown. The device 10 serves to localize and / or monitor nerves 11 located in the pelvic region 12 of a patient 13 and acting on one of the pelvic organs, namely in particular the bladder 14 and the rectum 15, during an operation, thus checking their integrity and / or functionality.

[0019] For performing intraoperative neuromonitoring, the device 10 has a nerve stimulator 16 in the form of a stimulation current generator 18 and a bipolar stimulation electrode 17 hand-held by the surgeon. The stimulation electrode 17 can be supplied with a stimulation current, which is supplied to it from the stimulation current generator 18 via a line 19. The device 10 further has a sensor device, designated as a whole by 20, which has as its main components an impedance measuring device 21 with a display 22 and several measuring electrodes 23 connected or connectable to the two pelvic organs, the bladder 14 and the rectum 15. The sensor device 20 further comprises a test current supply device 24 with test current electrodes 25 that can be applied to the two pelvic organs, the bladder 14 and the rectum 15.

[0020] The inventive design is such that two test current electrodes 25a, 25b and two measuring electrodes 23a, 23b are provided for each of the two pelvic organs. The arrangement in this case is such that one test current electrode 25a (or 25b) and one measuring electrode 23a (or 23b) are combined in one electrode unit. One of the four electrode units is designed as an electrode catheter 26a, which can be inserted into the patient's urethra 27 for application to the bladder 14, so that the electrodes located on the outer circumference of the catheter rest against the inside of the urethra and thus establish electrical contact with the bladder. Another of the electrode units is designed as a rectal probe 26b, which is inserted into the patient's anus 28.In the other two electrode units, the test current and measuring electrodes are designed as needle electrodes, which can be applied intramurally to the two pelvic organs 14, 15 at a distance from the electrode catheter 26a or the rectal probe 26b.

[0021] The test current electrodes 25 are connected to the test current supply device 24 via test current lines 29. Correspondingly, there are connecting lines 30 from the measuring electrodes 23 to the impedance measuring device 22, which is assigned an integrated measurement signal amplifier 31 in the form of a conventional dual-phase lock-in amplifier, with which the signals tapped by the measuring electrodes 23 are amplified and processed for a meaningful display on the screen 22. The manner in which measurement signals can be processed using a lock-in amplifier is known to those skilled in the art and will not be discussed in more detail here.

[0022] In the preferred embodiment of the invention, the impedance measuring device is an impedance spectroscope with which changes in the alternating current resistance (impedance) in the pelvic organs 14, 15 between the test current electrodes 25 and the measuring electrodes 23 can be detected and visualized to the surgeon on the display 22, which changes occur as a result of stimulation of the monitored nerve(s) 11 by means of the stimulation electrode 17 and a subsequent contraction of the muscle tissue of the pelvic organ in question.

[0023] The procedure is as follows: Using the test current supply device 24, a known and constant test current (alternating current) is impressed into the smooth muscle tissue of the bladder or rectum via the two test current electrodes 25a, 25b applied to the pelvic organ 14 or 15, respectively. The voltage across the measurement section resulting from the tissue impedance is tapped via the two measuring electrodes 23a, 23b. The impressed test current should not contain any direct current components, since electrolysis between the electrodes can occur due to the fluids in the tissue when direct current is applied.

[0024] The applied constant test current can preferably be modulated at a specific frequency (50 kHz). Since tissue impedance is not purely resistive, but rather complex, the imaginary impedance component (capacitive and inductive components) in the tissue creates a phase shift between the test current and the tapped voltage across the test section. Impedance is therefore preferably determined using the root mean square method.

[0025] The real part of the impedance of the organ tissue across the measurement path, determined in the manner described, corresponds to a purely ohmic resistance, while the imaginary part is determined by the capacitive and inductive components and is frequency-dependent. Changes in impedance can be clearly detected, for example, using impedance spectroscopy. In impedance spectroscopy, the modulation frequency of the test current is varied across a specific, defined frequency spectrum. This allows the tissue impedance to be determined as a function of the modulation frequency. Impedance changes can thus be detected particularly reliably.

[0026] The result of an impedance measurement with the device according to the invention according to Fig.1 by means of the four electrodes on each of the two pelvic organs, in response to several stimulation current pulse phases introduced at intervals into a nerve 11 to be monitored by means of the stimulation electrode 17, is in the Fig.2 shown graphically. As a result of a stimulation current pulse phase 32, which is expediently a sequence of rectangular pulses with a fixed pulse duration of, for example, 1 ms and a defined frequency of the sequence of, for example, 30 Hz, the signal is transmitted to the smooth muscle tissue of the affected pelvic organ 14 and / or 15 at the nerve 11 being monitored for integrity / functionality, resulting in a stimulation-induced muscle contraction and a concomitant change in the impedance across the measuring section between the measuring electrodes 23a, 23b applied to the organ. Accordingly, the voltage tapped between the measuring electrodes changes with a short time delay compared to the time of the stimulation current pulse phase, which is displayed to the surgeon on the screen 22, for example in a representation according to Fig.2, in which the impedance change or the voltage increase indicating this change is clearly visible as a spike 33 in the voltage curve. Restimulation of nerve 11 is possible by maintaining a rest phase 34 of less than 120 seconds, during which the contraction of the smooth muscle subsides and thus, in turn, the impedance increases across the measuring section.

[0027] Using the device according to the invention, it is therefore possible to reliably check nerves in a patient's pelvic region, particularly in the pelvis, for their integrity and functionality. The absence of an impedance change in the affected pelvic organ despite a triggered stimulation current pulse indicates that the nerve pathways between the stimulation site on the nerve and the targeted pelvic organ are damaged or completely interrupted, for example, because they were severed with a scalpel. Using the device, the surgeon can also first localize nerves in the often difficult-to-oversee surgical area in order to decide whether a planned incision can be performed without risking nerve damage.

Claims

1. Intraoperative neuromonitoring apparatus for locating nerves in the pelvic region of a patient and / or monitoring their integrity / functionality during an operation, having: - a sensor device (20) which can be connected to at least one pelvic organ (14; 15) of the patient (13) and comprises at least two measuring electrodes (23) which can be applied to the pelvic organ (14; 15) and an impedance measuring device (21) which is connected or can be connected to the measuring electrodes, - a display (22) for displaying impedance changes on the pelvic organ (14; 15) between the measuring electrodes (23), and having - a test current supply device (24) with at least two test current electrodes (25) which can be applied to the pelvic organ (14; 15), at least one nerve stimulator (16), which can be introduced into the operating area during the operation and is in the form of a stimulation electrode (17) to which a stimulation current can be applied, wherein the apparatus is configured to introduce a plurality of temporally spaced stimulation current pulses into a nerve (11) to be monitored by means of the stimulation electrode (17), characterized in that the apparatus is configured such that it measures the impedance changes between the measuring electrodes (23; 23b) on the pelvic organ (14; 15) on the basis of the time, which impedance changes result from the excitation by the stimulation electrode (17) with the stimulation current pulses, and displays the impedance changes on the basis of the time on the display such that a first impedance characteristic is visible at a first time in addition to a second impedance characteristic at a second time, wherein the first time is different from the second time.

2. Apparatus according to Claim 1, characterized in that one of the test current electrodes (25a; 25b) and one of the measuring electrodes (23a; 23b) are combined in an electrode unit (26a; 26b).

3. Apparatus according to Claim 1 or 2, characterized in that the test current supply device (24) provides an alternating test current which is applied to the test current electrodes (25) and has a fixed or adjustable test current frequency.

4. Apparatus according to one of Claims 1 to 3, characterized in that the test current supply device (24) comprises a plurality of, in particular two, test current electrode pairs with two test current electrodes (25a, 25b) each and means for generating alternating test currents with different test current frequencies at the different test current electrode pairs.

5. Apparatus according to one of Claims 1 to 4, characterized in that the sensor device (20) has a measurement signal amplifier (31), preferably a lock-in amplifier, particularly preferably a dual-phase lock-in amplifier, which conditions the measurement signal that can be tapped off at the measuring electrodes (23).

6. Apparatus according to one of Claims 1 to 5, characterized in that the impedance measuring device (21) essentially consists of an impedance spectroscope.

7. Apparatus according to one of Claims 2 to 6, characterized in that at least one electrode unit comprising one measuring electrode (23a; 23b) and one test current electrode (25a; 25b) is in the form of an electrode catheter (26a) and / or a rectal probe (26b).

8. Apparatus according to one of Claims 1 to 7, characterized in that the nerve stimulator (16) is a bipolar stimulation electrode (17).

9. Apparatus according to one of Claims 1 to 8, characterized in that the sensor device (20) has at least two measuring electrodes (23 a,b) and two test electrodes (25 a,b) each for application to the bladder (14) and to the rectum (15) of the patient.