Single neuron analysis of the human midbrain tegmentum. Rostral mesencephalic reticulotomy for pain relief

Rostral mesencephalic reticulotomy (RMR) has been performed since 1973 for relief of intractable pain. The target area is in the midbrain reticular formation (MRF) bordering the periaqueductal gray matter at the superior collicular level. The target of RMR is 13-16 mm posterior to the midpoint of the AC-PC line and 5-8 mm below the AC-PC line. The laterality of the target is measured from the center of the aqueduct, ranging 5 to 8 mm from the midline. The rationale for this procedure is based upon the previous findings that the brain stem reticular formations plays a more important role above the spinal cord level than the lateral spinothalamic tract in the central conduction of nociceptive impulse. In the present study, intraoperative single neuron recording was made with tungsten microelectrodes from the human midbrain tegmentum in response to peripheral pinprick stimulation. These nociceptive neurons were classified into three groups in regard to the unit latency from the peripheral pinprick stimulation.