Omar Hospital,
Jail Road,
Lahore, Pakistan.
Keyhole Surgery to cure Hemifacial Spasm and Trigeminal Neuralgia
Trigeminal Neuralgia
Trigeminal neuralgia is the term applied to a particular facial pain which is unique amongst the neuralgia in that the pain can nearly always be completely controlled by treatment. If the same treatment is mistakenly give to patients with other forms of facial pain, they are unlikely to be improved and be made worse.
The age of onset is usually over 50 years, and many patents are in the eighth or ninth decades; but it may start in patients as young as 25. Its occurrence in younger patients should arouse suspicion of associated disseminated sclerosis, a crebellopontine angle tumor or a vascular lesion. It is commoner in women.
The main clinical feature is the sudden and severe pain that only lasts a moment and then goes, leaving nothing behind – except the fear of its return. Shaving, talking, washing or even a cold wind may disturb the skin of the upper lip and trigger a paroxysm of pain which is so severe that the patient is immobilized in agony. It is initially localized to one division of the trigeminal nerve, usually the second, but with time tends to spread to other divisions and increase in severity. Its course is interrupted by remissions of months or years of complete freedom from pain, and an elderly patient may die of an unrelated cause without it returning. It my become bilateral, either soon after its onset or after years of unilateral pain.
The trigger area may be in the gums or teeth. Some patients are given dental treatment for what is in fact trigeminal neuralgia; others seem to develop trigeminal neuralgia after prolonged and painful treatment for dental disease. Rarely does the first paroxysm of pain occur in the ophthalmic division, but it may spread to the forehead from the cheek and later appear to start from behind the eye.
Microvascular decompression involves direct exposure of the trigeminal nerve rootlets in the cerbellopontine angle. In a high proportion of patients an artery is seen to indent or about the trigeminal roots, usually adjacent to the dorsal root entry zone. Interposing a small piece of sponge between artery and nerve gives pain relief in over 80% of patients. Although some question the mechanism involved, there is no doubt that this method produces excellent results whilst avoiding unpleasant sensory side-effects. The more major procedure however carries a 1% mortality risk and a treat of serious morbidity. For this reason it is best reserved for patients under the age of 70 years in good general health.
Hemifacial Spasm
Hemifacial spasm is a facial disorder that is not painful, but its proposed aetiology is so similar to trigeminal neuralgia that it is best described in this chapter. The condition is characterized by unilateral spasm of the facial muscles supplied by the facial nerve.
Clinical Features
The onset of hemifacial spasm usually commences in middle or old age and there is a sight female predominance. The spasms usually commence around the orbicularis oculi muscles and subsequently spread down the face to involve the other facial muscle innervated by the facial nerve. the spasm are episodic and are frequently precipitated by emotional distress, chewing, talking or laughing. The condition causes the patient considerable social embarrassment and the spasms of the orbicularis oculi result in eye closure making driving difficult.
In contrast to trigeminal neuralgia, where there is no clinical evidence of 5th cranial nerve dysfunction, there is frequently minor facial weakness between the episodes of spasm. Otherwise, there are no neurological findings.
The microvascular decompression is performed through a small posterior fossa craniotomy and using the operating microscope, the vessel compressing the 7th nerve at the brain stem junction is carefully mobilized away. The nerve is then protected from the vessel by a small patch of sponge. The operation is usually highly effective in relieving the spasm. There is a small risk of unilateral hearing loss due to the proximity of the 8th nerve and its blood supply. As the operation involves a craniotomy, often in elderly patients, there is a small risk of serious complication, mostly as a result of cerebrovascular complications. This possibility should temper an obvious enthusiasm for an effective operation.