Deafferentation pain and stimulation of the thalamic sensory relay nucleus: clinical and experimental study

This report summarizes our clinical experience in which the effects of both thalamic sensory relay nucleus (TSRN) and periaqueductal gray (PAG) stimulation were tested in the same series of patients with various forms of pain. The clinical data indicated that neurogenic pain due to deafferentation at the level of the peripheral nerves or the spinal cord was often controlled by TSRN stimulation but not by PAG stimulation. We also review the results of our experimental investigations in cats which were undertaken in an attempt to clarify the neurophysiologic basis of such differential clinical effects of TSRN and PAG stimulation. It appeared that abnormal hyperactivity within the trigeminal medullary dorsal horn following retrogasserian rhizotomy was far more frequently inhibited by TSRN stimulation than by PAG stimulation.