Trigeminal Neuralgia

Trigeminal neuralgia

Trigeminal neuralgia (tic douloureux) is a form of face pain, characterised by episodes of severe, sudden, electric shock like pain on one side of the face, often around the cheek, lip or jaw. It lasts only a few seconds, with repeated bursts over seconds to a few minutes. Episodes may occur over several weeks to months, followed by prolonged pain free periods.

Pain can be triggered by stimulation of the face, such as light touch, washing, shaving, chewing and eating. Pain relief can sometimes occur by firm pressure by the hands around, but not touching the trigger area. Incidence per year around 3-5 per 100,000. Age of onset usually 60s and older, but can occur in younger patients in presence of multiple sclerosis or brain tumour.

Cause is demyelination of the trigeminal (fifth cranial nerve) sensory fibres adjacent to brain stem. This can be caused by compression from an overlying blood vessel most commonly, and occasionally by the demyelination process of multiple sclerosis, and rarely by benign brain tumours (meningioma, acoustic neuroma).

Clinical examination of the face usually normal. Any neurological deficit on cranial nerve examination is indication for MRI, but routine imaging not indicated.

Medical treatment is the first option, and the following drugs are helpful, in order of frequency of use:

1. Carbamazepine starting at 100 mg twice daily, increasing between 1-2000 mg per day to obtain best effect with minimal side effects, which include sedation and problems with balance. Routine monitoring of liver, kidney and bone marrow function by blood tests needed.
2. Lamotrigine 50-400 mg per day. Adverse effects similar to carbamazepine.
3. Other anticonvulsant medications including gabapentin, phenytoin and clonazepam.
4. Newest medication is oxcarbazepine which is has promising results.
5. Baclofen 40-80 mg per day. Not often used.
6. Tricyclic antidepressants are widely used to treat nerve pains, but are not often used in trigeminal neuralgia
7. Morphine and similar medications do have a small indication for nerve pains, but should only be considered after other options exhausted.

If medications are not helpful or poorly tolerated, interventions can be considered:

1. Radiofrequency trigeminal ganglion lesion is a widely used technique. It is a simple day case procedure done under sedation and local anaesthetic. An insulated needle can be introduced through the skin and advanced to the nerve root under direct X-ray guidance. An electrical current can be passed down the needle to either heat the nerve or by pulsing produce a high electrical field around the nerve root. Success rates are generally high but recurrences may occur months or years later. The technique can be readily repeated. Side effects are rare including decreased facial sensation and can be minimised by keeping current and duration of treatment low.
2. Microvascular decompression is done less commonly and involves an operation in a neurosurgical unit. It is indicated if abnormal blood vessels are present. It is generally reserved for younger patients as duration of benefit is longer. Recurrences have, however, been reported. It appers to be a relatively safe procedure.