WO2020250140A1

WO2020250140A1 - Neuromonitoring device and apparatus and method of use during neurosurgery

Info

Publication number: WO2020250140A1
Application number: PCT/IB2020/055440
Authority: WO
Inventors: Jason John LABUSCHAGNE
Original assignee: Labuschagne Jason John
Priority date: 2019-06-11
Filing date: 2020-06-10
Publication date: 2020-12-17
Also published as: NL2023289B1

Abstract

This invention relates to a neuromonitoring device and apparatus which may be utilised together with a biopsy device, endoscope or an ablation device. The invention, further, relates to a method of utilising the neuromonitoring apparatus during neuromonitoring and surgery. There is provided for the neuromonitoring apparatus to be comprised of a cannula having an elongate working channel which is insertable into brain tissue of a patient; and an electrically conductive elongate member which is configured to be passed down the elongate working channel of said cannula, the surface of the electrically conductive elongate member being electrically insulated with an exposed electrically conductive portion located at a distal region of said electrically conductive elongate member and which is shaped and configured to be located in the outlet opening of the cannula, wherein, in use, the exposed electrically conductive portion transmits an electrical signal to the brain tissue of the patient and/or receives an electrical signal from the brain tissue of the patient.

Description

NEUROMONITORING DEVICE AND APPARATUS AND METHOD OF USE DURING

NEUROSURGERY

FIELD OF THE INVENTION

This invention relates to a neuromonitoring device and apparatus. More particularly, but not exclusively so, this invention relates to a neuromonitoring device which may be utilised, together with a biopsy device, endoscope or an ablation device during percutaneous intracranial monitoring and surgery. The invention further relates to a method of utilising the neuromonitoring device and apparatus during neuromonitoring and surgery.

BACKGROUND TO THE INVENTION

Diagnosis and treatment of conditions affecting the brain are notoriously difficult and complex. The brain is a delicate soft tissue structure that controls bodily functions through a complex neural network which is connected to the rest of the body through the spinal cord. Both the brain and the spinal cord are protected by bony structures which present unique challenges during the diagnosis and treatment of conditions affecting the brain. Furthermore, owing to the complex nature of the brain, it is of the utmost importance that the surgeon identifies and performs targeted investigation and/or treatment (e.g. ablation, stimulation, manipulation etc.) on the relevant lesion or tissue, whilst leaving surrounding brain tissue intact and undamaged, or at least minimising damage to surrounding tissue.

Typically, patients present with symptoms that require a physician to capture images of the brain. These images may reveal lesions of uncertain causes. In order to recommend the correct treatment, a physician may require a brain biopsy to obtain a specimen that a pathologist can review for an accurate diagnosis.

Often, a neurosurgeon will use stereotactic equipment to localize the preferable site for the biopsy, manipulation or surgery. This allows the neurosurgeon to map the brain in a three-dimensional coordinate system and select the appropriate target coordinates for guiding a biopsy needle/suction device and/or neuromonitoring probe. In mapping the brain, the neurosurgeon often employs a process known as stereotaxis. Stereotaxis is a process by which neurosurgeons use MRI or CT imaging studies, targeted algorithms and a computer to locate and target a tumour or other lesion inside the brain.

Stereotaxis processes and techniques have no doubt proved themselves to be of immense assistance to neurosurgeons.

Monitoring of neural elements can reduce the likelihood of neural damage during surgery near or in delicate neural structures. Signals from intra-operative neuromonitoring probes are recorded and evaluated for signs of irritation or damage to neural structures, via commercially available neuromonitoring devices. A disadvantage of these neuromonitoring devices is that neuromonitoring can only be done during open surgery which presents the known risks and complications to patients.

A further disadvantage of these processes and techniques is that these are employed prior to and separately from the biopsy, manipulation or surgery procedures that are required to be performed. In addition, different medical devices/instruments are employed to perform the different functions and procedures.

Owing to the complexity of the brain and its functions discussed above, the surgeon is accordingly necessitated to provide the utmost care when performing the different functions/procedures, as error in any brain procedure may prove damaging and often fatal to a patient.

This also necessitates the use of different medical devices in firstly monitoring neural elements, and secondly performing the requisite function following the particular diagnosis and establishing the treatment protocol.

Neuromonitoring ability of current neuromonitoring devices are furthermore constrained in that the exposed electrically conductive portion of the neuromonitoring device is presented on the forward distal tip of the neuromonitoring probe only. This requires meticulous placement of the neuromonitoring device by the surgeon and limits the potential area of monitoring substantially. This, in turn, requires the surgeon to move the neuromonitoring device quite substantially in order to monitor a larger area of brain tissue. In addition, current neuromonitoring probes require the neurosurgeon to manually determine the reach or depth of the tip probe before actuating/stimulating the probe. The current technologies are furthermore limited in terms of the depth of placing the probes into brain tissue.

A yet further disadvantage of current neuromonitoring technologies include the limitations of monitoring and/or detecting peripheral neural tissue stimulation, such as the limbs, in response to stimulating the relevant brain tissue and vice versa through a device placed in a minimally invasive fashion.

Despite many advances in medical technology, there accordingly still remains a need for a device and method by which brain tissue and lesions may be investigated directly and in real-time prior to biopsy, ablation, manipulation or surgery; in a more efficient manner and without the use of multiple devices and procedures.

OBJECT OF THE INVENTION

It is accordingly an object of the present invention to provide a neuromonitoring device and apparatus with which a neurosurgeon may intraoperatively and directly investigate brain tissue and lesions.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided a neuromonitoring device for a cannula, the cannula comprising:

an elongate working channel which extends from an inlet opening to an outlet opening, the elongate working channel being insertable into brain tissue of a patient, the neuromonitoring device comprising:

an electrically conductive elongate member which is configured to be inserted through the inlet opening of the cannula and to be passed down the elongate working channel of said cannula, the surface of the electrically conductive elongate member being electrically insulated with an exposed electrically conductive portion located at a distal region of said electrically conductive elongate member and which is shaped and configured to be located in the outlet opening of the cannula, wherein, in use, the exposed electrically conductive portion transmits an electrical signal to the brain tissue of the patient and/or receives an electrical signal from the brain tissue of the patient.

There is provided for the outlet opening of the cannula to take the form of a side window at a distal region of the elongate working channel and for the elongate working channel to terminate at a distal region, further, there is provided for the exposed electrically conductive portion of the electrically conductive elongate member to be shaped and configured to be located in the side window of the cannula.

There is provided for the cannula to take the form of any one of an endoscope and a neuro-navigation device.

The exposed electrically conductive portion may have electrical impedance spectroscopy capability. It is envisaged that the electrically conductive portion may have interdigitated electrodes for electrical impedance sensing. The exposed electrically conductive portion may be covered in a microelectrode array which is configured for multi-point electrical impedance sensing.

The neuromonitoring device may include a guide for receiving a complementary formation located on the cannula. The invention further provides for the neuromonitoring device to include a guideline which is complementary to a guideline of the cannula such that the exposed electrically conductive portion is operatively located in the outlet opening.

There is further provided for the neuromonitoring device to further comprise an adjustable sheath arrangement which is configured to reversibly cover a portion of the exposed electrically conductive portion.

The adjustable sheath arrangement may be separate from the neuromonitoring device and may be shaped and configured to be insertable through the inlet opening and passed down the elongate working channel of the cannula so as to, at least partially, encapsulate the neuromonitoring device. There is provided for the exposed electrically conductive portion to fit in the outlet opening by means of an integral attachment feature. The integral attachment feature may be any one of an annular snap-fit, a cantilever snap-fit and a torsional snap-fit.

According to a second aspect of the present invention, there is provided a neuromonitoring apparatus comprising:

- a cannula comprising an elongate working channel which extends from an inlet opening to an outlet opening, the elongate working channel being insertable into brain tissue of a patient; and

- an electrically conductive elongate member which is configured to be inserted through the inlet opening of the cannula and to be passed down the elongate working channel of said cannula, the surface of the electrically conductive elongate member being electrically insulated with an exposed electrically conductive portion located at a distal region of said electrically conductive elongate member and which is shaped and configured to be located in the outlet opening of the cannula, wherein, in use, the exposed electrically conductive portion transmits an electrical signal to the brain tissue of the patient and/or receives an electrical signal from the brain tissue of the patient.

The electrically conductive elongate member may include a guide for receiving a complementary formation located on the cannula. The invention further provides for the electrically conductive elongate member to include a guideline which is complementary to a guideline of the cannula such that the exposed electrically conductive portion is located in the outlet opening.

There is provided for the neuromonitoring apparatus to further comprise an adjustable sheath arrangement which is configured to reversibly cover a portion of the exposed electrically conductive portion.

The adjustable sheath arrangement may be shaped and configured to be insertable through the inlet opening of the cannula and passed down the elongate working channel of said cannula so as to, at least partially, encapsulate the electrically conductive elongate member.

It is envisaged that the electrically conductive elongate member may include a formation which is complementary to a formation disposed on the cannula for receiving the electrically conductive elongate member.

There is further provided for the exposed electrically conductive portion to fit in the outlet opening by means of an integral attachment feature. The integral attachment feature may be any one of an annular snap-fit, a cantilever snap-fit and a torsional snap-fit.

According to a third aspect of the present invention, there is provided a method of intra operative neuromonitoring using the neuromonitoring device and/or apparatus in accordance with the first and second embodiments, the method including the steps of:

- inserting, at least partially, the cannula into brain tissue of the patient;

- positioning the outlet opening of the cannula proximate the targeted brain tissue of the patient;

- inserting the electrically conductive elongate member into the inlet opening of the cannula;

- passing the electrically conductive elongate member down the elongate working channel of the cannula;

- aligning the exposed electrically conductive portion with the outlet opening of the cannula; and - transmitting an electrical signal to the targeted brain tissue of the patient and/or receiving an electrical signal from the targeted brain tissue of the patient, via the exposed electrically conductive portion and the electrically conductive elongate member.

The step of aligning the exposed electrically conductive portion with the outlet opening of the cannula may include the step of aligning a guideline provided on the electrically conductive elongate member with a complimentary guideline of the cannula such that the exposed electrically conductive portion is located in the outlet opening.

The invention yet further provides for the method of intra-operative neuromonitoring to be followed by the step of performing a biopsy including the steps of withdrawing the electrically conductive elongate member from the cannula and inserting a biopsy needle, suction device etc. and performing a biopsy.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Two embodiments of the invention are described below, by way of non-limiting examples only and with reference to the accompanying drawings in which: figure 1 is a perspective view of the neuromonitoring apparatus according to a first embodiment of the invention with the electrically conductive elongate member outside of the cannula; figure 2 is a perspective view of the neuromonitoring apparatus according to the first embodiment of the invention with the electrically conductive elongate member inside the cannula; figure 3 is a side view of the neuromonitoring apparatus according to the first embodiment of the invention with the electrically conductive elongate member inside the cannula; and figure 4 is a perspective view of a neuromonitoring apparatus according to a second embodiment of the invention with the electrically conductive elongate member outside of the cannula.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the accompanying drawings, in which like numerals refer to like features, a first embodiment of the neuromonitoring apparatus is generally indicated by reference numeral 10 in figures 1 to 3 and a second embodiment of the neuromonitoring apparatus is generally indicated by reference number 100 in figure 4.

As shown in figure 1 , the neuromonitoring apparatus 10 includes a cannula 12 and a neuromonitoring device in the form of an electrically conductive elongate member 14.

The cannula 12 includes an elongate working channel 16 which extends from an inlet opening 18 of the cannula 12 and terminates at a distal region 20 of the cannula 12. The cannula 12 has a side window 22 proximate the distal region 20 which operatively exposes an inside portion of the elongate working channel 16 to brain tissue (not shown) of the patient (not shown) which is adjacent to the side window 22. In a preferred embodiment of the invention, the elongate working channel 16 is made of an electrically conductive material (e.g. 304 stainless steel).

The electrically conductive elongate member 14 is configured to be inserted through the inlet opening 18 of the cannula 12 and to be passed down the elongate working channel 16 of the cannula 12. The electrically conductive elongate member 14 has an exposed electrically conductive portion 24 located at a distal region of the electrically conductive elongate member 14. The exposed electrically conductive portion 24 is shaped, sized and configured to be located in the side window 22 of the cannula 12. The remaining surface of the electrically conductive elongate member 14 is electrically insulated so as to not transmit an electrical current or signal between the elongate working channel 16 and the electrically conductive elongate member 14. The electrically conductive elongate member 14 is preferably manufactured from biocompatible Pebax® tubing and stainless steel.

The electrically conductive elongate member 14 further includes a cable 26 for transmitting an electrical signal which is received by the electrically conductive elongate member 14 to an EMG processor (not shown). As will be explained below, the processor may be utilised to calculate the electrical impedance to enable a surgeon to discriminate between different tissue types and to record and evaluate signs of irritation/damage to the relevant neural structure in the known manner.

In use, as shown in figures 2 and 3, the elongate working channel 16 is, at least partially, inserted into brain tissue (not shown) of a patient (not shown). Hereafter, the electrically conductive elongate member 14 is inserted through the inlet opening 18 of the cannula 12 and passed down the elongate working channel 16 of said cannula 12. The electrically conductive elongate member 14 is passed down the elongate working channel 16 of the cannula 12 until the exposed electrically conductive portion 24 fits within the side window 22 of the cannula 12. In this respect, guide lines 28 and 30 are respectively provided on the electrically conductive elongate member 14 and cannula 12 respectively to ensure proper alignment of the exposed electrically conductive portion 24 with the side window 22.

With the exposed electrically conductive portion 24 located in the side window 22 of the cannula 12, an electrical signal from tissue of the patient which is adjacent to the side window 22 may be transmitted to the EMG processing unit (not shown). Therefore, the electrical properties of the tissue which is adjacent to the side window 22 can be investigated by measuring the electrical impedance between the elongate working channel 16 and the exposed electrically conductive portion 24 as mentioned above.

In an alternative embodiment, the exposed electrically conductive portion 24 itself may have electrical impedance spectroscopy capability. The exposed electrically conductive portion 24 may have interdigitated electrodes (not shown) for electrical impedance sensing. In this embodiment, the electrical impedance between the interdigitated electrodes is measured, as opposed to the elongate working channel 16 and the exposed electrically conductive portion 24.

In a still further embodiment, the exposed electrically conductive portion 24 may be covered in a microelectrode array which is configured for multi-point electrical impedance sensing. It is known that the electrical impedance is considered as a prominent indicator to discriminate between tissue types and to investigate the biological behaviours or changes of biological matters due to its high sensitivity. For example, the differences of electrical impedances between normal and cancerous tissues have been reported on.

Therefore, by measuring the electrical impedance of tissue (not shown), the neuromonitoring apparatus 10 provides a surgeon with a real-time analysis of the tissue type and its characteristics which is adjacent to the side window 22 and exposed electrically conductive portion 24. The location of the side window 22 furthermore allows a distinct and enlarged geometry to which the stimulation current can be delivered. In addition, by manipulating the cannula 12, the side window 22 may be rotated through 360 degrees thereby increasing the potential area of monitoring, should this be required.

The neuromonitoring apparatus 10 is utilised to pass an electrical stimulus via the electrically conductive elongate member 14 to tissue (not shown) of the patient (not shown) which is adjacent to the side window 22. By passing an electrical stimulus to the exposed electrically conductive portion 24 of the electrically conductive elongate member 14, a stimulus can be applied to tissue (not shown) of the patient (not shown) to determine, by using standard intro-operative neuro-monitoring methods, including, but not limited to, EMG, motor evoked potentials, direct nerve stimulation, cortical and subcortical stimulation, if the tissue adjacent to the side window 22 and exposed electrically conductive portion 24 is eloquent tissue or not, and if it can or should be manipulated, biopsied or if it should be preserved.

The elongate working channel 16 may also have interdigitated electrodes or a microelectrode array configured along its length and on its surface. This will enable the surgeon to monitor tissue which is adjacent to the length of the elongate working channel 16. In this embodiment, additional cabling for transferring or communicating an electrical signal which is received by the elongate working channel 16, via the interdigitated electrodes or microelectrode array which is arranged along the length of the elongate working channel 16, to a processor (not shown).

As mentioned above, the guidelines 28 and 30 indicate to the surgeon when the exposed electrically conductive portion 24 is located in the side window 22 of the cannula 12 to avoid actuation of the electrically conductive portion 24 when not exposed in the side window 22. Such incorrect use may lead to undesired or irrelevant electrical signals in the elongate working channel 16 thereby providing incorrect information to the surgeon and/or damage tissue of the patient.

The exposed electrically conductive portion is also configured to fit in the side window by means of an integral attachment feature (not shown) to ensure that the two components are properly fitted in alignment for the operation described above. The integral attachment feature may be any one of an annular snap-fit, a cantilever snap-fit and a torsional snap- fit. Further to this feature, the electrically conductive elongate member may include a formation (not shown) which is complementary to a guide of the cannula for receiving a complementary formation of the cannula to ensure that the components are properly fitted. This minimises human error and promotes safety to the patient.

Furthermore, in this current embodiment, the distal-most tip of the distal region 20 is closed as shown. This prevents the surgeon from inserting the electrically conductive elongate member 14 to beyond the cannula 20 and furthermore ensures that the exposed electrically conductive portion 24 is aligned in length with the side window 22.

In alternative embodiment not shown, the neuromonitoring apparatus 10 includes an adjustable sheath arrangement (not shown) which is configured to reversibly cover a portion of the exposed electrically conductive portion 22 if required. The adjustable sheath arrangement (not shown) may take many forms. For example, the adjustable sheath arrangement (not shown) may take the form of a second cannula (not shown) which has a second, adjustable, side window (not shown). The second cannula (not shown) may be shaped and configured to encapsulate, at least partially, the electrically conductive elongate member 14, whilst said electrically conductive elongate member 14 is located in the working channel 16 of the cannula 12. Here, the second side window (not shown) would leave a portion of the exposed electrically conductive portion 22 exposed to tissue (not shown) which is adjacent to the side window 22 of the working cannula 16. The shape of the second side window (not shown) may be any form, including a circle, a rectangular, etc. The extent to which the second side window (not shown) exposes the exposed electrically conductive portion 24 may be adjustable. There is provided for the second side window (not shown) to be smaller in size than the side window 22 of the cannula 12. For example, the second side window (not shown) may be shorter in length or thinner than the side window 22 of the cannula 12. With reference to figure 4, the neuromonitoring apparatus 100 according to a second embodiment of the invention includes a cannula 120 and a neuromonitoring device in the form of an electrically conductive elongate member 140.

The cannula 120 includes an elongate working channel 160 which extends from an inlet opening 180 of the cannula 120 to an outlet opening of the cannula 120. In this embodiment, the cannula 120 takes the form of an endoscope.

The outlet opening 200 includes a window 220 which operatively exposes an inside portion of the elongate working channel 160 to tissue (not shown) of the patient (not shown) which is adjacent to the window 220.

The electrically conductive elongate member 140 is configured to be inserted through the inlet opening 180 of the cannula 120 and to be passed down the elongate working channel 160 of the cannula 120. The electrically conductive elongate member 140 has an exposed electrically conductive portion 240 located at a distal region of said electrically conductive elongate member 140. The exposed electrically conductive portion 240 is shaped and configured to be located in the window 220 of the cannula 120. In this embodiment, the length of the electrically conductive elongate member 140 in relation to the elongate working channel 160 is provided to such an extent that the exposed electrically conductive portion 240 extends only just beyond the window 22 of the cannula 120. This has the benefit of assisting the surgeon in determining the location of the tip of the exposed electrically conductive portion 240 thereby ensuring accuracy and certainty regarding the tissue to which the stimuli will be applied to thereby minimising or overcoming any human error.

The remaining surface of the electrically conductive elongate member 140 is electrically insulated so as to not transmit an electrical current or signal between the elongate working channel 160 and the electrically conductive elongate member 140. The electrically conductive elongate member 140 is preferably manufactured from biocompatible Pebax® tubing and stainless steel. The electrically conductive elongate member 140 further includes a cable 260 for transferring or communicating an electrical signal which is received by the electrically conductive elongate member 140 to an EMG processor (not shown).

There is provided for the exposed electrically conductive portion 240 to include the same features and functionality as it does according to the first aspect of the invention. Further, there is provided for the second embodiment of the invention to include guidelines and guide formations similar to the first embodiment of the invention.

In a yet further embodiment of the invention, the electrically conductive member (14, 140) is configured to act as a transmitter and receiver of electrical current. In this respect, electrodes (not shown) are placed proximate peripheral neural tissue, such as in or on the limbs. A surgeon may then stimulate the appropriate brain tissue and detect the stimulation, or lack thereof, at the electrodes placed in or on the limbs. Alternatively, the electrodes in or on the limb can be stimulated through the electrodes and the apparatus (10, 100) may then detect the stimulation, or lack thereof, at the appropriate location in the brain tissue. The apparatus of the invention may accordingly be used as both transmitter and receiver according to the type of testing interrogation the surgeon wishes to conduct. It will be understood that the setup of such transmitting and receiving functionality would be within the competence of a person skilled in the art and is accordingly not repeated herein.

It will be appreciated by those skilled in the art that the invention may be utilised during any percutaneous surgery procedure or intraoperatively (e.g. into an open wound site). For example, the invention could be utilised during spinal surgery, prostate surgery, gastro-intestinal surgery, a key-hole surgery procedure. The invention may prove to be particularly useful for surgeries where the target organ or tissue cannot be mapped accurately. Here, the transmitted electrical impedance signal, by itself, could be used to determine the accurate positioning and of the side window of the device.

A significant advantage of the current invention provides for neuro-navigated neuromonitoring as opposed to the known neuromonitoring during open surgery. In this respect, the cannula of the invention will be suitable for use as an endoscope and a neuro navigation device. This is particularly useful in that the surgeon is now able to properly assess the brain tissue before any biopsy, surgery or the like is performed. A further significant advantage includes that the surgeon can neuro-monitor brain tissue before a biopsy is performed leading to a more targeted and sound approach and perform the biopsy without having to insert a different cannula or similar device. In addition, invention may be utilized as both a transmitter and receiver as described above, without the need to incorporate different medical devices and procedures.

The utilization of a plurality of medical devices is furthermore avoided and the current invention provides the ability to provide a more satisfactory assessment of neural tissue and provide a minimally invasive procedure.

It will be appreciated by those skilled in the art that the invention is not limited to the precise details as described herein and that many variations are possible without departing from the scope of the invention. As such, the present invention extends to all functionally equivalent structures, methods and uses that are within its scope.

The description is presented by way of example only in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention. The words which have been used herein are words of description and illustration, rather than words of limitation.

Claims

1. A neuromonitoring device for a cannula, the cannula comprising:

- an elongate working channel which extends from an inlet opening to an outlet opening, the elongate working channel being insertable into brain tissue of a patient,

the neuromonitoring device comprising:

- an electrically conductive elongate member which is configured to be inserted through the inlet opening of the cannula and to be passed down the elongate working channel of said cannula, the surface of the electrically conductive elongate member being electrically insulated with an exposed electrically conductive portion located at a distal region of said electrically conductive elongate member and which is shaped and configured to be located in the outlet opening of the cannula,

wherein, in use, the exposed electrically conductive portion transmits an electrical signal to the brain tissue of the patient and/or receives an electrical signal from the brain tissue of the patient.

2. The neuromonitoring device of claim 1 , wherein the outlet opening of the cannula is a side window at a distal region of the elongate working channel; the elongate working channel terminates at a distal region; and wherein the exposed electrically conductive portion of the electrically conductive elongate member is shaped and configured to be located in the side window of the cannula.

3. The neuromonitoring device of claim 1 , wherein the cannula is any one of an endoscope and a neuro-navigation device.

4. The neuromonitoring device of claim 1 , wherein the exposed electrically conductive portion has electrical impedance spectroscopy capability.

5. The neuromonitoring device of claim 4, wherein the electrically conductive portion has interdigitated electrodes for electrical impedance sensing.

6. The neuromonitoring device of claim 4, wherein the exposed electrically conductive portion is covered in a microelectrode array which is configured for multi-point electrical impedance sensing.

7. The neuromonitoring device of claim 1 , wherein the neuromonitoring device includes a guide for receiving a complementary formation located on the cannula.

8. The neuromonitoring device of claim 1 , wherein the neuromonitoring device includes a guideline which is complementary to a guideline of the cannula such that the exposed electrically conductive portion is operatively located in the outlet opening.

9. The neuromonitoring device of claim 1 , wherein the neuromonitoring device further comprises an adjustable sheath arrangement which is configured to reversibly cover a portion of the exposed electrically conductive portion.

10. The neuromonitoring device of claim 9, wherein the adjustable sheath arrangement is separate from the neuromonitoring device and is shaped and configured to be insertable through the inlet opening and passed down the elongate working channel of the cannula so as to, at least partially, encapsulate the neuromonitoring device.

1 1. The neuromonitoring device of claim 1 , wherein the exposed electrically conductive portion fits in the outlet opening by means of an integral attachment feature.

12. The neuromonitoring device of claim 1 1 , wherein the integral attachment feature is any one of an annular snap-fit, a cantilever snap-fit and a torsional snap-fit.

13. A neuromonitoring apparatus comprising:

14. The neuromonitoring apparatus of claim 14, wherein the outlet opening of the cannula is a side window at a distal region of the elongate working channel; the elongate working channel terminates at a distal region; and wherein the exposed electrically conductive portion of the electrically conductive elongate member is shaped and configured to be located in the side window of the cannula.

15. The neuromonitoring apparatus of claim 13, wherein the exposed electrically conductive portion has electrical impedance spectroscopy capability.

16. The neuromonitoring apparatus of claim 15, wherein the electrically conductive portion has interdigitated electrodes for electrical impedance sensing.

17. The neuromonitoring apparatus of claim 15, wherein the exposed electrically conductive portion is covered in a microelectrode array which is configured for multi point electrical impedance sensing.

18. The neuromonitoring apparatus of claim 13, wherein the electrically conductive elongate member includes a guide for receiving a complementary formation located on the cannula.

19. The neuromonitoring apparatus of claim 13, wherein the electrically conductive elongate member includes a guideline which is complementary to a guideline of the cannula such that the exposed electrically conductive portion is located in the outlet opening.

20. The neuromonitoring apparatus of claim 13, wherein the neuromonitoring apparatus further comprises an adjustable sheath arrangement which is configured to reversibly cover a portion of the exposed electrically conductive portion.

21. The neuromonitoring apparatus of claim 20, wherein the adjustable sheath arrangement is shaped and configured to be insertable through the inlet opening of the cannula and passed down the elongate working channel of said cannula so as to, at least partially, encapsulate the electrically conductive elongate member.

22. The neuromonitoring apparatus of claim 13, wherein the exposed electrically conductive portion of the electrically conductive elongate members fits in the outlet opening by means of an integral attachment feature.

23. The neuromonitoring apparatus of claim 22, wherein the integral attachment feature is any one of an annular snap-fit, a cantilever snap-fit and a torsional snap-fit.

24. The neuromonitoring apparatus of claim 13, wherein the cannula is any one of an endoscope and a neuro-navigation device.

25. A method of intra-operative neuromonitoring using the neuromonitoring apparatus of claim 13, the method including the steps of:

inserting, at least partially, the cannula of the neuromonitoring apparatus into brain tissue of the patient;

positioning the outlet opening of the cannula proximate the targeted brain tissue of the patient;

inserting the electrically conductive elongate member into the inlet opening of the cannula;

passing the electrically conductive elongate member down the elongate working channel of the cannula;

aligning the exposed electrically conductive portion with the outlet opening of the cannula; and

transmitting an electrical signal to the targeted brain tissue of the patient and/or receiving an electrical signal of the targeted brain tissue of the patient, via the exposed electrically conductive portion and the electrically conductive elongate member.

26. The method of claim 25, wherein the step of aligning the exposed electrically conductive portion with the outlet opening of the cannula includes the step of aligning a guideline provided on the electrically conductive elongate member with a complimentary guideline of the cannula such that the exposed electrically conductive portion is located in the outlet opening.

27. The method of claim 25, wherein the cannula is any one of an endoscope and a neuro-navigation device.

28. The method of claim 25, wherein said method is followed by the step of performing a biopsy including the steps of:

withdrawing the electrically conductive elongate member from the cannula; - inserting a biopsy needle, suction device and the like; and

performing a biopsy.