Following a number of requests from readers, this week's column deals with a chronic pain condition called trigeminal neuralgia.
One correspondent describes her experience like this: "I am suffering a great deal with a throbbing, sensitive, 'jagged' pain emanating from the side of my nose up to and incorporating the general eye area. Having gone to have eyes, nose and sinuses checked out it appears that I have a form of trigeminal neuralgia. It is a most persistent and wearing sensation leading to sleepless nights."
Trigeminal neuralgia is a characteristic pain in the area of the face covered by the fifth cranial nerve. This nerve has three large branches that fan out on both sides of the face. It is both a sensory and a motor nerve, so when it malfunctions, it can cause pain and a physical reaction such as facial twitching. In the past, the facial muscle seizure gave rise to another name for the condition, "tic douloureux".
The diagnosis is made on the patient's history alone, based on the characteristic features of the pain. It occurs in paroxysms lasting from a few seconds to two minutes. The frequency of the paroxysms varies greatly; from hundreds of attacks a day to periods of remission that can last for years. The pain is severe and is described by patients as intense, sharp, superficial, stabbing, or like an electric shock in character. It is often triggered by touching a specific area on the face or by eating, talking, washing the face or cleaning the teeth.
Trigeminal neuralgia is more common in women and the incidence also increases with age, rising to 45 cases per 100,000 people aged over 80 years.
The exact cause of the neuralgia remains unclear. The nerve may be damaged in some way along its path, and it has been suggested that it may be compressed by blood vessels. But a neurological examination is usually normal.
What is not in doubt is that the pain of trigeminal neuralgia is different from, say, the acute pain experienced following a fracture or a surgical operation. Pain that is stabbing or shooting in nature is called neuropathic or nerve pain. Its treatment is quite different from that of acute pains which usually respond to aspirin, codeine or morphine.
Instead, the first line approach to a "nerve pain" such as trigeminal neuralgia is to use anti-convulsants - drugs more usually associated with the treatment of epilepsy. Carbamezepine is often the first choice treatment. A recent review of the medical literature found that one in three people respond to the drug. One report into the long-term benefits of carbamezepine found initial success in 70 per cent of patients, but that after five years or longer only 22 per cent found it to be still effective.
A newer anti-convulsant, lamitrogine, has been shown to help the pain of neuralgia when added to other anti-convulsant treatments. However, despite anecdotal reports of success, there is no solid evidence to back up the use of other drugs such as phenytoin, clonezepam, sodium valproate or gabapentin.
What about surgical treatments? Again, although the injection of the nerve with alcohol, phenol or local anaesthetic has been carried out with some success, there is no evidence from good quality medical trials to support these interventions. Newer treatments such as the use of radio-frequency thermocoagulation and peripheral laser treatment - in which a laser beam is applied to the skin over the nerve - have yet to be subjected to randomised controlled trials to assess their effectiveness.
Chronic trigeminal pain - one which has lasted longer than six months after onset - should be assessed by a multi-disciplinary team. Because chronic pain has physical, psychological and psycho-social components, the best treatment results follow an assessment by a doctor, a physiotherapist, occupational therapist and a psychologist. Each member of the team then contributes to the overall treatment plan.
Typically, a patient might receive anti-convulsants, relaxation therapy, an exercise programme and cognitive behavioural therapy as part of a comprehensive pain management programme. Having a plan to deal with any crisis and joining a self-help group are also important. Although chronic pain may be hard to eradicate completely, a broad approach to pain management will guarantee a significant reduction in symptoms and renewed quality of life.