2 The procedure
2.1.1 Stereotactic radiosurgery with the gamma knife is used to treat trigeminal neuralgia. This is a condition characterised by sudden bursts (paroxysms) of facial pain. These bursts may be triggered by touch, talking, eating or brushing teeth. The pain occurs in the areas supplied by the trigeminal nerve: the cheeks, jaw, teeth, gums, lips and, less often, around the eyes or forehead. Trigeminal neuralgia is rare; the annual incidence is 4 per 100,000 population.
2.1.2 Some people with mild symptoms recover without treatment. For most people, the paroxysmal bursts of severe pain continue indefinitely.
2.1.3 The first-line treatment for trigeminal neuralgia is medication. Surgery is considered for people who experience severe pain despite medication, or who have adverse effects from medication.
2.2.1 Gamma knife radiosurgery involves aiming a focused beam of radiation at the trigeminal nerve at the point where it leaves the brain. It does not require skin incision, needle insertion or general anaesthesia.
2.2.2 Other treatments for severe trigeminal neuralgia include: glycerol injection, which involves inserting a needle into the nerve under X-ray guidance; radiofrequency treatment, which involves applying short bursts of radiofrequency energy to the nerve through a needle; and balloon microcompression, which involves inflating a balloon near the nerve. All of these are minimally invasive surgical procedures. Microvascular decompression is a more invasive procedure that involves opening the skull.
2.3.1 This procedure was the subject of a systematic review commissioned by the Institute and completed in January 2004. The review reported that between 33% and 90% of patients achieved complete pain relief immediately after stereotactic radiosurgery using the gamma knife. After a mean follow-up period of 18 months, the proportion of patients with recurrence of pain ranged from 0% to 34%, with an average of 14%. For more details, refer to the Sources of evidence section.
2.4.1 The most common complication reported was facial numbness, affecting 8% (139/1757) of patients. New or worsened trigeminal nerve dysfunction was reported in 4% (66/1757) of patients. Facial paraesthesia occurred in 2% (33/1757) of patients. Less commonly reported complications included troublesome dysaesthesia, loss of taste, corneal numbness and deafness. For more details, refer to the Sources of evidence section.
2.5.1 These recommendations were based only on evidence on the use of the gamma knife. It is noted that other forms of stereotactic radiation treatment exist.
2.5.2 There is a lack of long-term data and the condition can recur.
2.5.3 Although the recurrence rate appears to be higher after stereotactic radiosurgery than after other treatments, the patient groups reported were not comparable. Relapse is most common in patients with multiple sclerosis and atypical neuralgia.