Somatosensory evoked potentials following trigeminal nerve stimulation in trigeminal neuralgia.

The examination of somatosensory evoked potentials following trigeminal nerve stimulation in 20 subjects with idiopathic trigeminal neuralgia revealed a pathological increase in latency of the first positive component on the involved side in 7 (41%) of the 17 patients without antecedent surgical treatment. The mean difference in latency between the two sides was 1.3 msec (2p greater than or equal to 0.005). These results are indicative of microtraumatization of the trigeminal nerve in the posterior fossa by blood vessels, for example, leading to local demyelinization. The method seems to be of diagnostic value in selecting patients for more decompression by posterior fossa operations.