What is trigeminal neuralgia?
Trigeminal neuralgia is a specific type of facial pain. It causes brief spasms of sharp pain in the distribution of the trigeminal nerve. This nerve has three main branches which provide sensation to different parts of the face and the pain is usually in the distribution of one of these three branches.
Typically the pain is brought on by light touch to specific parts of the face or inside the mouth and it may be triggered by heating, swallowing, smiling, washing, shaving or even and cold breeze blowing on the face. The pain lasts only a few seconds and may occur once or twice a day or many times an hour. In between the sharp pains there are usually no symptoms.
Trigeminal neuralgia usually starts for no apparent reason and may go away spontaneously only to return again at a later date.
What causes it?
In most cases the cause of trigeminal neuralgia is unknown. The most commonly held theory is that it is due to a loop of an artery in close proximity to the trigeminal nerve as it comes off from the brain stem. It is thought that the pulsation of the artery against the nerve triggers the pain. In rare cases, trigeminal neuralgia may be due to tumours near the trigeminal nerve or multiple sclerosis. It is usual for an MRI scan of the brain to be done when trigeminal neuralgia is first diagnosed to rule out these other causes.
How is it treated?
Trigeminal neuralgia responds poorly to most analgesic drugs. The most commonly used drug is Carbamazepine (Tegretol) which is a drug used for epilepsy. In most cases this will significantly reduce the episodes of pain or even relieve them altogether. The dose is gradually increased until the pain disappears or side effects occur. The side effects most commonly experienced are unsteadiness, dizziness and drowsiness. Occasionally patients can be allergic to these drugs. This usually causes a skin rash and if this happens the drugs should be stopped and advice obtained from your GP. Carbamazepine can also rarely affect blood cell production and your GP should check this early in your treatment. If Tegretol does not help or if an allergic reaction prevents its use, other anti-convulsants such as Lyrica (Pregabalin), Valproate (Epilim) or Gabapentin (Neurontin) may be used in addition, or instead of Carbamazepine.
In some cases of trigeminal neuralgia, depending on which particular parts of the nerve are involved, it may be possible to freeze the nerve and provide temporary relief. The main problem with this is that it does produce numbness in the distribution of that nerve.
There are several neurosurgical procedures available that can help, but it is important to note that they will only work for trigeminal neuralgia and not other types of facial pain.
All treatments for trigeminal neuralgia have a relatively high recurrence rate, although in general the recurrence rate is less for the more invasive procedures. In deciding on the best treatment, the success rate and recurrence rate needs to be considered along with the seriousness of the procedure.
In most cases I would recommend a glycerol injection as the first treatment after anticonvulsants, as it is simple and can be done as a day patient. It is particularly useful for patients who cannot have a Janetta procedure due to coexisting medical illness. If the glycerol injection fails or there is a recurrence of pain, a Janetta procedure may be recommended. This is an intracranial operation and requires a general anaesthetic, a week in hospital and 4 to 6 weeks off work. There are other neurosurgical procedures that are done less commonly for trigeminal neuralgia. These include balloon compression of the trigeminal ganglion and surgical division of part of the trigeminal nerve intracranially. In some centres, stereotactic radiotherapy (radiosurgery) is being used with some success.