Neuronal hyperactivity in experimental trigeminal deafferentation

Abstract

✓ Postoperative facial paresthesias frequently occur in patients following retrogasserian rhizotomy. To investigate the etiology of these paresthesias, microelectrode recordings of neuronal activity were made from the brain stem of the cat at variable times after trigeminal root section. Spontaneous neuronal hyperactivity was recorded from the deafferented spinal trigeminal nucleus in animals studied 8 to 10 days following rhizotomy. After this time the hyperactivity was found to progressively increase and was greatest in animals 1 month after rhizotomy, which was the longest time interval between rhizotomy and microelectrode recordings studied. The neuronal hyperactivity was similar to single cell recordings from cerebral epileptic foci both in monkey and man. This supports earlier experimental information that neuronal deafferentation is a factor in the development of epileptic activity. The authors postulate that brain-stem neuronal hyperactivity similar to epileptic activity is the physiological correlate of paresthesias that occur after sectioning the root of the trigeminal nerve. Further, if retrogasserian rhizotomy causes neuronal seizure activity in the spinal trigeminal nucleus, it may also be possible for trigeminal deafferentation produced by certain pathological processes involving the trigeminal nerve or ganglion to be the basis for other sensory disorders involving the face, i.e., trigeminal neuralgia.