--Disease Characteristics-- Idiopathic trigeminal neuralgia - Paroxysmal attacks of facial or frontal pain lasting a few seconds to less than 2 minutes - Pain has at least 4 of the following characteristics: Distribution along one or more divisions of the trigeminal nerve Sudden, intense, sharp, superficial, stabbing, or burning quality Pain intensity severe Precipitation from trigger areas, or by certain daily activities such as eating, talking, washing the face, or cleaning the teeth Between paroxysms entirely asymptomatic - No neurological deficit - Attacks are stereotyped in the individual patient - Exclusion of other causes of facial pain by history, physical examination and special investigations when necessary Must be uncontrolled or refractory as defined by occurrence of at least 2 paroxysms of pain per day despite conventional treatment with maximally tolerated doses of carbamazepine --Prior/Concurrent Therapy-- No concurrent medication for trigeminal neuralgia other than carbamazepine, phenytoin, and neurontin Concurrent medication for other conditions allowed Concurrent medication must be on stable dose(s) --Patient Characteristics-- Hepatic: No significant hepatic disease Renal: No significant renal disease Neurological: No evidence of progressing neurological disorder (e.g., intracranial neoplasm, multiple sclerosis) Other: No history of drug abuse Not pregnant Effective contraception required of all fertile patients