GB2261067A

GB2261067A - Identifying nerve axons

Info

Publication number: GB2261067A
Application number: GB9123118A
Authority: GB
Inventors: Terence Frederick Knibb
Original assignee: British Aerospace PLC
Current assignee: BAE Systems PLC
Priority date: 1991-10-31
Filing date: 1991-10-31
Publication date: 1993-05-05
Also published as: GB9123118D0

Abstract

An apparatus (10) for identifying nerve axons (18) comprises a thermal sensor (14) for sensing heat in a nerve axon caused by the passage of a nerve impulse therealong and a monitor (16) for displaying a thermal image. Alternatively an LED arrangement may be used to indicate presence/absence of heat in the nerve axon. A signal processing means (20) is provided for processing the image signal and a stimulation means (22) may be provided for stimulating the passage of a nerve impulse along an axon (18). A timing means may be provided for timing the passage of an output from the thermal imaging device and/or the signal processing means to coincide with the stimulation of an axon (18) thereby to enhance to image quantity. In operation, the thermal sensor (14) is focused on the nerve axons (18) and an operator views monitor (16) in order to identify a nerve axon. <IMAGE>

Description

APPARATUS FOR AND METHOD OF IDENTIPSYING NERVE AXONS The present invention relates to an apparatus for and method of identifying nerve axons in a human or animal body and relates particularly, but not exclusively, to an apparatus suitable for use in neurosurgery.

Nerve axons connect the brain to the various muscles in the body and act to transmit electronic impulses from the brain to the muscles whenever it is necessary to activate said muscles.

Damaged nerve axons can either fail to transmit the electronic impulses or can transmit spurious impulses which result in undesirable muscle activity. The passage of electronic impulses through nerve axons is via a sodium-potassium ion transfer which results in small quantities of heat being generated within the axon whenever an impulse is passed.

Modern surgical techniques enable surgeons to repair damaged nerve axons when identified. However, it is extremely difficult to identify one single damaged nerve axon amongst a bundle of closely packed nerve axons. Current identification techniques can involve surgery to expose the nerve axons themselves and the use of well known stimulation techniques in order that the surgeon can observe any functional impairment.

Such an identification technique relies on disturbing the nerve axons which can in itself cause damage and relies heavily on the skill of the surgeon for correct identification.

There is therefore a requirement to provide an effective apparatus for and method of identifying nerve axons which is less damaging and which does not rely so heavily on the skill of a surgeon for correct identification.

Accordingly, the present invention provides an apparatus for identifying nerve axons in a human or animal body, the apparatus comprising detection means for detecting a change in the state of a nerve axon caused by the passage or termination of a nerve impulse along said nerve axon.

It will be appreciated that by providing such a detection means it will be possible to identify the position of a particular nerve axon without damaging the nerve axons or relying on the skill of the surgeon.

Preferably, the detection means comprises a thermal sensor for detecting a change in temperature of the nerve axon. The use of a thermal sensor enables identification to be achieved by monitoring a natural nerve axon activity.

The detection means may comprise a thermal imaging device which in operation is focused on the nerve axons thereby to detect a change in temperature of a nerve axon and a visual monitor or other indicator for displaying a resultant thermal image of the nerve axons. Such a system significantly increases the ease of identification.

In a particularly advantageous arrangement the detection means comprises a long wave infra red type thermal imager, thereby to allow non invasive identification of nerve axons.

The apparatus may include stimulation means for stimulating the passage of a nerve impulse along a nerve axon thereby to increase the accuracy andlor speed of identification.

Advantageously the apparatus may include signal processing means for processing the output of the thermal imaging device and for enhancement of the image presented on the monitor.

The signal processing means may be operable to average a number of outputs from the thermal imaging device thereby to enhance the accuracy of the apparatus.

Preferably, a timing means is provided for timing the passage of an output from the thermal imaging device and! our the signal processing means to coincide with the stimulation of the nerve axon thereby to increase identification accuracy.

A method of identifying nerve axons in a human or animal body may include the steps of: directing a thermal sensor device at a nerve axon, displaying an output from the thermal sensor device on a monitor or other indicator and identifying a nerve axon by the thermal image on said monitor or other indicator.

The method may include the further step of stimulating the passage of a nerve impulse along a nerve to be identified.

The present invention will now be more accurately described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic/schematic representation of a patient and an apparatus for identifying nerve axons according to the present invention.

Figure 2 is an exploded view of portion A in figure 1 and illustrates the grouping of nerve axons in greater detail than shown in figure 1.

Referring to the drawings in general, but particularly to figure 1. The apparatus 10 for identifying nerve axons in a human or animal body 12 comprises a thermal sensor in the form of a thermal imaging device 14 and a monitor 16 linked to the thermal imaging device 14 for displaying a thermal image. The apparatus further includes a signal processing means 20 for processing the image signal output from the imaging device 14, a stimulation means 22 for stimulating the passage of a nerve impulse along a nerve axon 18 and a timing means 24 for timing the passage of an output from the thermal imaging device and/or the signal processing means to coincide with the stimulation of the nerve axon 18.

The detection means 14 may comprise a long or medium wave infra red type thermal imager. Such imagers can be focused on the exposed nerve axons to enable nerve identification to be achieved without disturbing the nerve axons themselves. It will however be appreciated that similsP thermal imagers may be used and that other types of detectors may be used. The stimulation means 22 may comprise an electric shock device having an attachment 22a positioned around the patient's head 12a as shown or it may comprise any one of a number of such similar devices well known for use in stimulating the passage of an electrical impulse along the length of a nerve axon and therefor not described herein.

The signal processing means 20 is operable to enhance the accuracy and quality of the image presented on the monitor 16.

For example, processing could include the steps of averaging a number of outputs in order to present an enhanced, more stable, image to the surgeon. Random variations can be smoothed out whilst causal variations can be added together in order to provide an enhanced image.

It will be appreciated that whilst the present invention has been described with reference to a visual monitor 16 other types of monitor or indicators could be used. For example a simple arrangement of L. E D. '5 could be used to indicate the presence or absence of a heat signal when the thermal sensor is passed over the individual nerve axons.

In operation, the thermal imager 14 is focused on the nerve axons to be identified and a thermal image output signal is passed therefrom to the signal processing means 20 for processing as required. The processed output signal is passed through the timing device 24 and onto the monitor 16 for displaying. The timing device may, in conjunction with the stimulation means 22, be operated such that it only passes an output signal to the monitor 16 whenever the stimulation means 22 is operated to pass an impulse along one or more of the nerve axons being viewed. If this timing technique is used, it will be possible to ensure the surgeon views the thermal image only when it is reasonable for him to expect one or more of the nerve axons to be transmitting a nerve impulse thereby increasing the accuracy of recognition. Alternatively, the timing means may be operated such that an image is continuously presented on the monitor regardless of whether or not a nerve axon has been stimulated. It will however be appreciated that it will then be somewhat more difficult to identify a nerve axon as the surgeon will be presented with an ever changing image.

Claims

1. An apparatus for identifying nerve axons in a human or animal body, the apparatus comprising detection means for detecting a change in the state of a nerve axon caused by the passage or termination of a nerve impulse along said nerve axon.

2. An apparatus as claimed in claim 1 in which the detection means comprises a thermal sensor for detecting a change in temperature of the nerve axon.

3. An apparatus as claimed in claim 1 or claim 2 in which the detection means comprises a thermal imaging device which in operation is focused on the nerve axons thereby to detect a change in temperature of a nerve axon and a visual monitor or other indicator for displaying a resultant thermal image of the nerve axons.

4. An apparatus as claimed in any one of the preceding claims in which the detection means comprises a long or medium wave infra red type thermal imager, thereby to enable non invasive identification of nerve axons.

5. An apparatus as claimed in any one of the preceding claims including stimulation means for stimulating the passage of a nerve impulse along a nerve axon.

6 An apparatus as claimed in any one of claims 2 to 5 including signal processing means for processing the output of the thermal sensor device.

7. An apparatus as claimed in claim 6 in which the signal processing means is operable to average a number of outputs from the thermal imaging device andlor the signal processing means thereby to enhance the accuracy of the apparatus.

8 An apparatus as claimed in claim 6 in which the signal processing means is operable to smooth random non causal variations andlor add causal variations in the outputs from the thermal imaging device andlor the signal processing means.

9 An apparatus as claimed in claim 7 or claim 8 including timing means for timing the passage of an output from the thermal imaging device and/or the signal processing means to coincide with the stimulation of the nerve axon.

10. A method of identifying nerve axons in a human or animal body including the steps of: directing a thermal sensor device at a nerve axon, displaying an output from the thermal sensor device on a monitor or other indicator and identifying a nerve axon by the presence or absence of a signal on the monitor or other indicator.

11. A method as claimed in claim 9 including the steps of stimulating the passage of a nerve impulse along a nerve axon to be identified.

12. An apparatus for identifying nerve axons in a human or animal body substantially as hereinbefore described and as illustrated in figures 1 and 2 of the accompanying drawings.

13. A method of identifying nerve axons in a human or animal body substantially as hereinbefore described and as illustrated in figures 1 and 2 of the accompanying drawings.