[Microvascular decompression of the trigeminal nerve: electrophysiological changes]

In a 67-year-old woman with trigeminal neuralgia, pressure on the trigeminal nerve of vascular bundle and arachnoidal adhesions was relieved by microsurgery. Short-latency, brainstem, trigeminal evoked-potentials were continuously recorded throughout the operation. The initial response was characterized by prolonged latency, low amplitude and distorted shape. Immediately after decompression the response attained normal latency, amplitude and shape. Pain disappeared within less than 24 hours. Power spectrum analysis showed wide frequency range in the initial evoked potentials, consistent with desynchronization of the afferent impulses. The range of frequencies was reduced to normal as soon as the trigeminal nerve was decompressed.