Short-latency, brainstem, trigeminal evoked-potentials

Short-latency, evoked-potentials were recorded from over the scalp in response to electrical stimulation of the upper lip, using the Microshev 4000 equipment (Microshev Co., Efrat). Normative data were obtained from 35 normal volunteers. The brain-stem, trigeminal evoked-potentials (BTEP) consisted of 4 distinct, well-reproduced waves evoked in less than 10 msec. The waves, named after their respective latencies, are thought to be generated in the preganglionic trigeminal nerve (T1), the postganglionic nerve entry zone (T2), in the trigeminal nucleus (T3) and the upper brainstem (T5). BTEP was recorded in nearly 200 patients suffering from various lesions in the peripheral trigeminal parts, tumors affecting the brainstem (before, during and after surgery) and in varying degrees of post-traumatic coma. BTEP proved to be a reliable tool for evaluating the brainstem trigeminal system; changes in its pattern reliably reflected altered activity of that system. It can be used for diagnosis as well as for intraoperative monitoring of brainstem function.