Introduction

Trigeminal neuralgia (facial pain) is characterised by brief episodes of intense, stabbing, electric shock-like pain on the face. These episodes occur spontaneously or can be triggered by light touch, chewing, or changes in temperature (i.e. cold). The pain is so intense as to be completely disabling. In addition, weight loss is common because oral triggers prevent affected individuals from eating enough to maintain adequate nutrition.

A less common form of the disorder, called" a typical trigeminal neuralgia", may cause less intense, constant, dull burning or aching pain, sometimes with occasional electric shock-like stabs.

Trigeminal Neuralgia

Cause

The cause of this condition is irritation of the fifth cranial nerve (the Trigeminal nerve) which is responsible for providing facial sensation. This irritation is occasionally due to benign tumors or multiple sclerosis, either of which can usually be detected by a high quality MRI of the brain.

In the majority of cases, however, imaging of the brain does not reveal a cause of the nerve irritation. In such cases a small vessel (usually an artery but occasionally a vein) is often found at operation to be compressing the root entry zone of the Trigeminal nerve at the brainstem.

Treatment

Trigeminal neuralgia is an eminently treatable condition.

The first line of therapy consists of medications such as Carbamazapine and Gabapetin. In most cases, medical treatment is effective.

If medical treatment fails or is limited by significant side effects, we have good surgical options for patients with trigeminal neuralgia surgery is usually ineffective for atypical trigerminal neuralgia. .

Surgical Options

Micro vascular Decompression - surgery through the skull, which removes or insulates the responsible blood vessel(s) using microsurgery - is an effective method of treating many people with this disorder. This is done under general anesthesia.

After the operation, the majority of patients have no facial numbness and are pain-free, requiring no further medications.

It is a major operation, and is not without danger. Hearing loss & Facial Weakness can occur on the side of the operation. Most of the serious and life-threatening complications have occurred in patients above 65-70 years of age. It is less effective for patients who have had other operations in the past.

Percutaneous Radiofrequency Gangliotomy uses a special needle inserted in the face and radiofrequency-generated heat energy to selectively damage the preganglionic trigeminal rootlets in Meckel's cave. It is carried out in the awake patient and requires his co-operation and accurate feedback for proper positioning of the needle.

This procedure causes irreversible facial numbness. Precise control of the extent of the lesion is not always possible. Abnormal, unpleasant sensations of itching, burning or crawling (in 20% of patients) can accompany facial numbness. When severe (0.3%), they are as distressing to the patient as their original pain, since they can be present continuously as a severe burning discomfort (anaesthesia dolorosa or analgesia dolorosa) which does not respond to treatment. Loss of feeling in the first Trigeminal division makes the cornea insensate, and leaves the patient at risk for corneal ulceration and can lead to loss of vision.

Percutaneous Glycerol Chemoneurolysis is also carried out using a needle inserted in the face and and this can be performed under general anesthesia. There is usually only mild sensory loss and rare oculomotor or dysesthetic sequelae. It has the same risks of meningitis and needle misdirection injury as any percutaneous technique. Compared with radiofrequency gangliotomy, the pain recurrence rate is higher, but this is not a significant disadvantage, as the procedure can be easily repeated and is well tolerated.

Gamma Knife Radio surgery i.e. focused radiation treatment performed without opening the skull, using intense gamma rays directed at the Trigeminal nerve root, has also been carried out for more than 10 years in Singapore. Reports so far have considered 50-90% reduction of pain as good and 10-50% as fair. No pathologic data is available regarding the immediate and long-term effects of high dose radiation (70-90 gy) to the nerve adjacent to the brain stem.

Surgical Choices & Risk Factors

The choice of operation depends on the patients’ age, associated illness and assessment of the risks he is willing to assume. For most "younger" patients, microvascular decompressions the best option. Younger patients have a better chance of tolerating surgery without complication, and a longer future life expectancy in which to deal with problem that can be follow percutaneous lesioning. They also have a higher risk of pain recurrence following such procedures and will likely need more future treatment resulting in an increased cumulative side effects.

Older patients (> 65-70 years of age) have increased risks of surgical complication. but because of shorter overall life expectancy, they are likely to require fewer repetitions of percutaneous producers with less cumulative denervation sequelae. Significant associated illness such as diabetes millitus can also increase the risk of such major surgery.