JPH0231968B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an intraoperative nerve multifunctional testing device that makes it possible to easily test continuity of damaged nerves during surgery.

[Background of the invention]

Injury to peripheral nerves or the junction of peripheral nerves to the spinal cord presents with severe motor and sensory paralysis of the innervating muscles and skin, respectively. However, recent advances in microsurgical techniques have made it possible to surgically repair these damaged peripheral nerves. it is,
The foundations are the introduction of surgical microscopes, advances in microsurgical tools, and the development of microsutures. Despite the results of peripheral nerve surgery using these techniques, the rate of complete recovery is still quite low.

From the perspective of surgical technology, microsurgical techniques and the tools and materials required for them have been developed primarily around microvascular anastomosis surgery, which has a more complex internal structure and function than blood vessels. This can be said to be due to the delay in the development of tools specific to peripheral nerve surgery and intraoperative nerve function testing equipment that can be used to repair peripheral nerves.

Up until now, surgeons have made decisions regarding various types of peripheral nerve repair surgery based primarily on macroscopic findings of nerve damage during surgery. However, even if the continuity of the nerve is recognized macroscopically or microscopically, functionally the nerve fibers may undergo Wallerian degeneration (even if the membrane covering the nerve fibers remains, the nerve fibers themselves may be damaged due to damage). In many cases, the nerves are so degenerated that they are unable to function at all, or they are simply a continuation of scar tissue.

In such cases, if it were possible to easily determine the functional continuity of the nerve and the degree of damage during surgery, it would be possible to perform nerve ablation (surgery to remove the scar tissue around the nerve while maintaining nerve continuity). The regenerated nerve can then be transferred to the peripheral area by removing the nerve scar and then microsurgically suturing the freshened nerve stumps together. This provides useful clues for determining the suitability for surgery (operation to relieve paralysis by passing it through the side).

Conventionally, for this purpose, tests and measurements such as nerve trunk conduction tests, motor nerve conduction velocities, and sensory nerve conduction velocities have been performed. However, all of these methods rely on responses or potentials obtained through muscle and skin sensory receptors, and they are used only when there are two or more damaged nerve sites in one nerve trunk (double).
nerve fibers), or when the regenerated nerve fibers are peripheral to the injured area and have not yet reached muscles or sensory receptors, there may be no conduction or no potential measurement even though the nerves have passed through the injured area. It will be judged as impossible. Therefore, such determination results are not directly useful for diagnosing the degree of nerve damage limited to the injured site. For this reason, testing the nerve conductivity in segments of the nerve trunk centered around the injured area is an effective means of directly determining the presence or absence of continuity of nerve fibers in the injured area and the degree of damage.

There have already been a few reports on methods of electrically stimulating nerves across the injured nerve trunk and deriving the resulting electric potential from the nerves.
However, conventional testing machines of this type were originally designed for preoperative, non-invasive diagnosis, and were therefore too large and difficult to handle for use during surgery.
It was difficult for the operator to operate it himself.

Next, we will discuss the intraoperative nerve function tests required for nerve suturing or nerve grafting when there is no continuity of nerve fibers at the peripheral nerve injury site or when the nerve is clearly ruptured macroscopically. state

Inside the peripheral nerve trunk runs a bundle of nerve fibers called a nerve bundle covered by several perineural membranes. In actual surgery, nerve suturing is performed using a microscope for each nerve bundle (nerve bundle suturing method). An essential issue in this nerve bundle suturing is that the nerve bundles at both stumps are correctly sutured, the sensory nerve bundle to the sensory nerve bundle, and the motor nerve bundle to the motor nerve bundle. It is known that if this joining is performed incorrectly, misdirection will occur, which will greatly impede post-operative nerve regeneration. Therefore, it is required to identify the function of each bundle of both stumps (funicular orientation) prior to nerve bundle suturing.

Anatomically, each nerve bundle has the characteristic of running in a complex plexus structure while exchanging nerve fibers with each other within the nerve trunk, and the pattern of nerve bundles at each cut plane differs depending on the level. In addition, there are differences between the left and right sides and between individuals, and according to the intraneural to-popographic atlas that has been published so far,
Although it is possible to know a certain tendency of the course of each nerve bundle, it cannot be used for each example of an actual surgical operation.

Therefore, we developed a method for identifying severed nerve bundles using electrophysiological techniques. In other words, the surgery is performed under epidural paralysis, and the position of the sensory nerve bundles in the stump is determined by the patient's sensory response to electrical stimulation given to each nerve bundle in the central nerve stump, while the patient's voluntary motor awareness is Therefore, motor nerve impulses are derived from the stump and the position of the motor nerve bundle is confirmed. In cases of fresh rupture (within approximately 3 days after injury), in the distal stump, electrical stimulation of the nerve bundle can be used to stimulate the motor nerve bundle using myoelectric potential from the innervating muscles, and mechanical stimulation of the skin (such as brushing or compression) can be used to stimulate the motor nerve bundle. It was found that the positions of sensory nerve bundles can be identified by the sensory nerve action potentials evoked by It was also found that when nerve bundle suturing was performed based on the results of this identification, the post-operative nerve recovery was better than when conventional identification was not performed. Despite the effectiveness of this identification method, one of the reasons why it is still used only in some facilities is that nerve bundle identification devices based on this identification method have not yet become generally easy to use. This can be said to be because it is not commercially available.

By the way, recently, surgical repair techniques for brachial plexus injuries have begun to be performed. That is,
Damage near the junction between peripheral nerves and the spinal cord (nerve roots) is repaired by nerve ablation or free nerve grafting. However, this repair technique is also ineffective if the injury is ruptured or pulled out centrally to the ganglion, and is only effective if the injury is peripheral to the meridian ganglion.

Therefore, it is important to determine whether the injury is a postganglionic nerve root injury, which can be expected to be surgically repaired, or a preganglionic injury, which cannot be repaired. Therefore, it is extremely useful to determine whether there is functional continuity at the junction between the spinal cord and nerve roots by measuring spinal cord potentials or somatosensory evoked potentials through peripheral nerve stimulation. Furthermore, if the injury is preganglionic, motor nerves in the periphery have undergone Wallerian degeneration, but sensory nerves have not. It can be used to determine if there is a subsequent injury.

The conventional method for measuring sensory nerve action potentials, which is induced by electrical stimulation of the skin and obtained by averaging them, takes time to add the averages, and the skin that can be electrically stimulated is limited, so it is difficult to test. There were two drawbacks: the nerves were limited.

[Key points of the invention]

We have investigated a method that can test sensory nerve action potentials in any nerve in an extremely short period of time during surgery. We considered that it can be used to determine whether it is post-articulation. That is,
If mechanical stimulation of the skin produces sensory nerve action potentials from the torn nerve root despite complete motor paralysis, the injury is preganglionic and surgical nerve repair is not possible. It turns out. If there is nerve root damage, first confirm functional peripheral nerve-spinal cord continuity by measuring somatosensory evoked potentials. Next, once a functional disruption is diagnosed, whether it is preganglionic or postganglionic is determined by the presence or absence of sensory nerve action potentials caused by mechanical stimulation.

In accordance with the above principles, the intraoperative nerve multifunctional testing device of the present invention is capable of (1) testing the continuity of peripheral nerves or spinal cord, (2) testing the nerve bundle identification of the peripheral nerve section, and (3) testing the peripheral nerve/spinal cord. It has a basic function of functional inspection of joints, and is configured to be selectable by mode switching.

[Embodiments of the invention]

The details of the present invention will be explained below with reference to Examples.

FIG. 1 schematically shows an embodiment of the intraoperative nerve multifunctional testing device according to the present invention, in which reference numeral 1 is a nerve bundle to be tested, 2 is a stimulation probe, and 3 is a detection probe. 4 is an intraoperative operation unit/display unit (hereinafter referred to as the operation unit) for setting various parameters and use modes, 5 is a connection cable, 6 is the main body of the multi-purpose testing device for controlling the test and signal processing, and 7 is the probe. Signal lines for probe connection, 8 are stimulation electrodes integrated into the stimulation probe, and 9 are bipolar electrodes for detecting nerve impulses integrated into the detection probe.

FIG. 2 shows the configuration of FIG. 1 in more detail. In the figure, reference numeral 10 is an isolator for stimulation pulses, 11 is a low-noise differential amplifier, 12 is an isolation amplifier, 13 is a bandpass filter for noise suppression, 14 is an AD converter, 15 is a microcomputer, 16 is a control circuit, 17 is a stimulation pulse generation circuit, 18 is a key operation unit, 19 is a display device, 2
0 is a DA converter, and 21 and 22 are output terminals.

Next, the operation of the apparatus will be explained for each inspection function.

(1) Peripheral nerve or spinal cord continuity test Stimulation pulses generated by the stimulation pulse generation circuit 17 inside the multifunctional testing device main body 6 are sent into the stimulation probe 2 via the cable 5, the operating section 4, and the signal line 7. The stimulation electrode 8 is applied to the nerve bundle through the stimulation electrode 8 which is electrically insulated by the isolator 10 . This electrical stimulation pulse generates an impulsive action potential (hereinafter referred to as a nerve impulse) in the normal nerve fibers in the nerve bundle 1, which propagates through the nerve fibers in the length direction (two directions). . This propagating nerve impulse is transmitted to the nerve impulse detection probe 3 via the detection bipolar electrode 9 that is in contact with the outside of the nerve bundle.
The signal is detected by a low-noise differential amplifier 11 built in the probe 3, electrically isolated by an isolation amplifier 12 also built in the probe 3, and then guided to the main body 6 via the operating section 4.

When nerve fibers within a nerve bundle are degenerated or damaged,
The propagation speed of nerve impulses decreases, or sometimes they become undetectable. Even nerve impulses propagating through normal nerve fibers have extremely weak amplitudes when detected outside the nerve bundle, at most a few μV (microvolts). Therefore, the differential amplifier 11 at the first stage of the amplifier used for amplifying nerve impulses has particularly low noise (when the input is short-circuited, the input conversion noise voltage is low in the band of 100Hz←10Hz).
1μV peak-to-peak or less), and the common-mode suppression ratio is sufficiently large to remove external common-mode noise (more than 80 dB at low frequencies).
It is essential that In addition, the detection bipolar electrode 9
Use one with as low impedance as possible and low noise comparable to the differential amplifier described above.

The nerve impulse detected by the low-noise differential amplifier 11 passes through the isolation amplifier 12 and bandpass filter 13, and then is sent to the AD converter 14.
The signal is converted into a digital signal and taken into the microcomputer 15. The signal detected in this way contains a lot of various noises, and the signal-to-noise ratio (S/N ratio) is not necessarily good. Therefore, the microcomputer 15 performs arithmetic averaging and moving average calculations to reduce irregular noise.

FIG. 3 schematically shows a stimulation pulse waveform a, a detected nerve impulse waveform b, and their temporal relationship. The stimulation pulse generation circuit 17 generates pulses with a repetition period T,
A trigger signal is sent to the control circuit 16 at the moment of occurrence. This allows AD to be adjusted based on the time of stimulation.
By synchronously adding the converted sequential periodic waveforms N times on the memory, the nerve impulse waveform can be averaged. Especially when there is a lot of noise, high frequency noise can be suppressed by calculating a moving average (number of moving samples M).

As shown in Figure 3, the propagation delay time T _P from the application of the stimulation pulse until the nerve impulse is detected is determined by the distance between the stimulation electrode and the detection electrode being L, and the propagation velocity of the nerve impulse being U. Then, it is given by T _P =L/U. Since the propagation speed and waveform change depending on the degree of nerve damage, the stimulation period T is kept at a constant ratio with the sampling period of AD conversion (Ts), and the observed waveform or propagation delay time T _P Depending on the situation, the operator may need to change it.

Also, the number of additive averages N, the number of moving average samples M
The operator must also be able to select the appropriate signal depending on the S/N ratio of the signal. After these processes, the nerve impulse waveform and propagation delay time T _P are as follows:
Continuous close monitoring must be available during intraoperative continuity testing. For this reason, the operation section 4 includes a small display device 19 such as a liquid crystal graphic display, and a key operation section 18 having several key switches for setting parameters T, N, and M, and for setting the mode of use. It has the following.

There are three usage modes: nerve continuity testing mode, nerve bundle identification testing mode, and nerve/spinal cord junction testing mode, and the microcomputer 15 controls processing functions, parameters, etc. according to the set usage mode. Make the switch.

In addition to being output to the display device 19 of the operation unit 4, the results of the signal processing performed as described above are
It is also output to the output terminal 21 via the DA converter 20, and can be recorded (in two types: waveform and print). In addition to this, there is another output terminal 2
2, the output from the band filter 13 can be directly monitored. By connecting this output terminal 22 to a speaker, it is possible to obtain an effective acoustic monitor for detecting nerve impulses buried in noise during surgery.

In addition, when this device is used for spinal cord continuity testing, the only difference is that the nerve bundle 1 in Figure 1 is replaced with the spinal cord, and the shapes of the electrodes 8 and 9 are slightly changed, and basically the case described above is used. The same operation is performed.

(2) Nerve bundle identification test at the peripheral nerve section.Detection of motor nerve impulses generated by the patient's voluntary motor awareness at the central section, and sensory nerve impulses caused by peripheral skin stimulation. In both cases of detection at the distal cut plane, a part of the apparatus having the configuration shown in FIG. 1 or 2 is used as is. That is, in the block diagram of FIG. 2, a nerve impulse is detected from the nerve bundle 1 via the bipolar electrode 9, amplified by the low-noise differential amplifier 11 and isolation amplifier 12, passed through the bandpass filter 13, and then output to the output terminal. You can observe from 22. In this case, only the presence or absence of reception of nerve impulses is detected without using the stimulation pulse generation circuit 17.

In this case, an effective method for investigating the sensory nerves of the peripheral nerves is to apply repeated mechanical stimulation and detect the evoked nerve impulses. As the stimulation probe 2, a mechanical stimulation probe 25 consisting of a power amplifier 23 and a solenoid type vibrator 24 as shown in FIG. 4, or a high voltage power amplifier 26 and a piezoelectric element as shown in FIG. A mechanical stimulation probe 28 consisting of 27 is used. Note that the nerve impulses induced by this repeated mechanical stimulation do not have a constant propagation delay time T _P as in the test (1) above;
Since T _P has a certain distribution, the effect of averaging is not so great, but the signal processing mechanism can be used as is.

(3) Functional test of peripheral nerve/spinal cord junction Essentially, the only difference is the electrode shape and parameters such as time and amplitude, and the basic circuit function is shown in Figures 1 and 2. It is the same as the thing. In other words, a stimulation electrode is attached to the central side of the damaged nerve and stimulation pulses are applied.
On the other hand, a coiled detection probe is attached to the scalp over the cerebral sensory cortex on the opposite side of the damaged nerve to detect signals.

By the way, the electrodes used in the present invention may be conventionally available commercially available electrodes, but in that case, it is necessary to hold and operate two sets of electrodes separately. This is quite complicated during surgery. Therefore, good results can be obtained by using a probe 29 as shown in FIG. 6 for testing peripheral nerve continuity.
This probe 29 is provided with a fixed bipolar electrode 30 and a movable bipolar electrode 31 at its tip. The movable bipolar electrode 31 moves on a sliding potentiometer 32, and the distance between the electrodes can be interpreted as a change in electrical resistance. As a result, one of the bipolar electrodes 30 and 31 is stimulated,
On the other hand, when a nerve impulse is detected, the nerve impulse conduction velocity can be automatically calculated by the microcomputer 15 of FIG.
It is displayed on the display device 9 of the operation section 4.

〔Effect of the invention〕

As described above, according to the present invention, for any nerve site damaged in various ways,
Highly reliable continuity and other tests can be performed with simple operations during surgery, and useful data can be quickly obtained in determining the details of the surgery.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an apparatus according to one embodiment of the present invention;
Figure 2 is a detailed diagram, Figure 3 is a signal waveform diagram of stimulation pulses and nerve impulses, Figures 4 and 5.
Each figure is a block diagram of an embodiment of a mechanical stimulation probe, and FIG. 6 is a block diagram of an embodiment of a probe having a structure in which a stimulation probe and a detection probe are integrated. In the figure, 1 is a nerve bundle, 2 is a stimulation probe, 3 is a detection probe, 6 is the main body of the multifunctional testing device, 13
is a band filter, 15 is a microcomputer,
16 is a control circuit, 17 is a stimulation pulse generation circuit, 1
8 is a key operation unit, and 19 is a display device.

Claims (1)

[Claims] 1. A first probe generating electrical stimulation and a second probe generating mechanical stimulation used to stimulate the nerve bundle, and a third probe of bipolar electrode configuration used to detect nerve impulses. and a coil-shaped fourth probe, an examination section to which each of the probes is connected, an operation section for setting the operation mode and operation parameters of the examination section, and a display section for displaying the waveform of the detected nerve impulse. When the first operation mode is set, the testing section uses the first and third probes to periodically generate stimulation pulses to detect the first
a function of receiving a nerve impulse applied to the third probe and output from the third probe, and detecting a conduction state between both probes and a propagation delay time of the nerve impulse, and when a second operation mode is set. Using the second and third probes, a stimulation pulse is periodically generated and applied to the second probe, and an output signal of the third probe is monitored to detect whether a nerve impulse is received. and when the third operating mode is set, using the first and fourth probes, the operating parameters of the period and amplitude of the stimulation pulse applied to the first probe are set to the operating parameters in the first operating mode. It is characterized by having a function of changing the parameter to a preset value different from the parameter, detecting the output signal of the fourth probe, and operating in the same manner as in the first operation mode. Intraoperative neurological multifunctional testing device.