The trigeminal evoked potential: Part II. Intraoperative recording of short-latency responses.

Short-latency (< 10 msec) trigeminal evoked potentials were studied intraoperatively in 31 patients under general anesthesia. Stimulation was performed peripherally in the face as well as centrally at the trigeminal nerve root entry zone. Recordings were made directly from the trigeminal root entry zone and far field from the scalp. Two principal negative deflections were noted, N1.6 and N2.6; and two waves that were less constantly identified were N.9 and N4-6. The latencies of these responses necessitated an extra-axial origin. It was concluded that this technique provided the ability to monitor the integrity of the extra-axial trigeminal nerve, but not the central trigeminal circuitry.