DIAGNOSTIC TECHNOLOGY

Through analysis of clinical symptoms and signs, the clinician may be able to localise the site and even the cause of a nerve lesion. However, adjunctive diagnostic tests are often required to clarify the location and aetiology of the problem.

Neurophysiology

Neurophysiology techniques are used to measure the conduction velocity and amplitude of nerve action potentials and adequacy of muscle innervation. Some terms that may be encountered are sensory action potentials, motor evoked potentials, nerve conduction velocity, electromyography (EMG), compound motor action potential, fibrillation or fasciculation, interference patterns, somatosensory evoked potential (SSEP) and F-Wave response.

Intraoperative electrophysiology

Intraoperative electrophysiology can improve the results of nerve repair or removal of nerve tumours. For example, if direct intraoperative nerve conduction studies show a healthy nerve action potential for a neuroma-in-continuity, it may be better to allow spontaneous nerve recovery rather to resect and graft the injured nerve segment. Somatosensory potentials during surgery following brachial plexus injury can be correlated with MRI findings to evaluate the extent of (proximal) nerve root avulsion as opposed to injury of more distal nerve elements.

3-Tesla MR scanning

MR imaging of nerves and muscles, in practice for more than a decade, has seen extraordinary refinements in technology and interpretation in recent years. Use of an MR scanner with 3 tesla rather than 1.5 tesla magnet increases the resolution of imaging of nerves and surrounding structures. It is now usually possibly to visualise clearly abnormalities in nerve texture, nerve entrapments, and nerve tumours. Scanning of the cervical spinal cord after brachial plexus injury can detect avulsion of nerve roots and guide appropriate treatment.

Ultrasonography

Technology and interpretation have advanced for ultrasound studies of nerves, just as for MRI studies. Advantages of neurosonography are its ability to produce “dynamic” images of nerves, for example subluxation of the ulnar nerve over the epicondyle with elbow flexion and its availability in the operating theatre. Intraoperative Neurosonography is a modern method used in quickly imaging unexposed parts of the operating site in a simple manner and custom tailor the surgical approaches accordingly.

THERAPEUTIC TECHNOLOGY

The appropriate use of the operating microscope and/or high resolution HD endoscope, provides better intraoperative visualization and identification of the pathology to be treated, thus improving patient outcomes.

Commonly used techniques in primary nerve reconstruction involve microminiature nerve suturing [with or without nerve grafting] and nerve transfers. These are ideally undertaken as soon as possible after a nerve lesion has occurred.

Primary Nerve Reconstruction

Commonly used techniques in primary nerve reconstruction involve microminiature nerve suturing (with or without nerve grafting) and nerve transfers. These are ideally undertaken as soon as possible after a nerve lesion has occurred.

Nerve grafting was brought into use in the 1970’s to avoid the tension and disruption that might occur when two ends of a cut nerve are approximated under tension. A dispensible nerve, commonly the sural nerve at the ankle, is sacrificed and segments are sutured or glued into place to bridge the nerve gap. Nerve fibres then regenerate through the living Schwann cells and other cells in the transplanted nerve segment.

Nerve transfers

Nerve transfers, especially some of their technical refinements, have been in common use for two decades only and are useful where there is no natural source of regenerating nerve fibres, for example after avulsion of spinal roots contributing to the brachial plexus. One standard nerve transfer is from the spinal accessory nerve (to the trapezius muscle) to the major nerve (suprascapular) to the rotator cuff muscles of the shoulder. Initially after successful re-innervation of rotator cuff muscle by fibres from the spinal accessory nerve, the patient will have to consciously shrug his/her shoulders in order to raise the arm at the shoulder. However, through plasticity of central connections to the motor nerve cells, the patient quickly learns to initiate the new movement subconsciously.

Secondary functional reanimation

These strategies are used in both long standing, untreated nerve lesions as well as when the primary nerve repair has falied to produce the expected level of muscle strength even under disciplined physical therapy for more than one and a half or two years.

Secondary reanimation of a lost function can be employed years or even decades after the initial nerve injury. Regional tendon and muscle transfers and free functional muscle transplantation (FFMT) are the salient techniques to bring forth lost function to an extremity.

Secondary reanimation of a lost function can be employed years or even decades after the initial nerve injury. Regional tendon and muscle transfers and free functional muscle transplantation (FFMT) are the salient techniques to bring forth lost function to an extremity.

Tendon transfer: in this technique tendons of functionally intact and compensable muscles of the anatomical neighbourhood are moved around and connected to the tendons of a paralysed muscle. For example, in wrist drop, tendons of compensable muscles of the antagonistic aspect of the forearm ( pronator teres, flexor carpi ulnaris, flexor digitorum superficialis and palmaris longus) are rerouted to the extensor tendons to effectuate wrist, finger and thumb extention as well as thumb abduction. The new function of the transferred tendon has to be relearned and mastered, butressing the importance of physical therapy after such procedures. Depending on the individual case results can be expected starting from three months after the procedure.

Muscle transfer foresees the transposition of a muscel bulk of the anatomical neighbourhood to effectuate a lost function. For example, latissimus dorsi is transposed in a unipolar fashion to the arm and attached to the biceps tendon, in order to achieve elbow flexion. The function of the transferred latissimus dorsi is compensated by the teres major muscle in its entirity. Initial results are seen in the majority of the cases after a period of three to frour months after such muscle transfers.

Free functional muscle transplantation (FFMT) is a technique employed when no dispensable muscles and/or tendons are available in the anatomical neighbourhood for reanimating a lost function. In this procedure a muscle flap is harvested based on its nourishing blood vessels and its motor nerve and autotransplanted to the recipient site. Here the blood circulation and reinnervation are reestablished using microminiature vessel anastomoses and nerve sutures. Trace movements of the transplanted muscle can be usually seen three to six months after surgery. Strenghthening of the FFMT occurs under physical therapeutic support during a period of one to one and a half years after the surgical procedure.

Cyberknife Technology

Over the past decade, Cyberknife technology has come to play an important role in the treatment of not only hard accessible tumors, but also in several painful nerve lesions, such as trigeminal neuralgia.

Cyberknife is one of several techniques for delivering high doses of ionising radiation to a small volume of tissue with minimisation of collateral damage (radiosurgery). Although most commonly used for treatment of tumours of the brain and other body organs, Cyberknife is also appropriate for trigeminal neuralgia. The radiation is generated by a small linear accelerator which is mounted on a robot to aim the beams. The head does not need to be immobilised in a rigid stereotactic frame as its position is monitored by a pair of orthogonal X-rays before every beam is delivered.

A patient receiving Cyberknife treatment for trigeminal  [Cyberknife] neuralgia must undergo MRI and CT scans of the brain according to an established protocol a week or so before the actual treatment. Then the target site and radiation dosage are prescribed by a clinician and the number and direction of beams of radiation are planned by a physicist using sophisticated computer programmes. Then the patient must lie for an hour or less with the head loosely immobilised in a meshed mask while approximately 100 beams are delivered from different directions. This is an outpatient procedure.

Neuromodulation

(microvoltage electrical stimulation of dorsal spinal cord or peripheral nerves or motor cortex or thalamic nuclei, depending on individual indications for these procedures) is a modern technology being increasingly employed to achieve pain reduction or even relief in chronic intractable and refractory neuropathic pain. Effectiveness of neuromodulative treatment for chronic pain syndromes of various causes has been demonstrated in several clinical trials and has shown to reduce the necessity of intake of pain medication.

al damage (radiosurgery). Although most commonly used for treatment of tumours of the brain and other body organs, Cyberknife is also appropriate for trigeminal neuralgia. The radiation is generated by a small linear accelerator which is mounted on a robot to aim the beams. The head does not need to be immobilised in a rigid stereotactic frame as its position is monitored by a pair of orthogonal X-rays before every beam is delivered.

A patient receiving Cyberknife treatment for trigeminal  (Cyberknife) neuralgia must undergo MRI and CT scans of the brain according to an established protocol a week or so before the actual treatment. Then the target site and radiation dosage are prescribed by a clinician and the number and direction of beams of radiation are planned by a physicist using sophisticated computer programmes. Then the patient must lie for an hour or less with the head loosely immobilised in a meshed mask while approximately 100 beams are delivered from different directions. This is an outpatient procedure.