Therapy of trigeminal neuralgia secondary to multiple sclerosis.

Trigeminal neuralgia occurs in approximately 1-2% of patients suffering from multiple sclerosis. Its pathophysiology is common to idiopathic forms and resides in altered properties of the sensory axonal membrane at the root entry zone into the pons, leading to parossistic firing. Antiepileptic drugs of the sodium channel blocker type, such as carbamazepine, lamotrigine, and phenytoin are highly effective in controlling pain. However, side effects on the CNS may, at higher doses, severely worsen the already impaired neurologic conditions in multiple sclerosis patients. Baclofen, a presynaptic muscle relaxant is also beneficial in trigeminal pain. Whatever the drug, habituation and loss of efficacy are likely to occur sooner or later. Symptomatic, neurolesive surgery is indicated in cases resistant or intolerant to medical therapy. Radiofrequency thermorhizotomy, either monitored by trigeminal evoked potentials or not, is the recommended procedure, as it may be considered the most reliable as far as localization and degree of lesion are concerned.