An Electrophysiologic Study of Ascending Pathways from Nucleus Caudalis of the Spinal Trigeminal Nuclear Complex

Abstract

O BSERVATIONS originally made by Sjiiqvist al and confirmed by other neurosurgeons10,25,a0,ag,40 indicate tha t nucleus caudalis s,26 of the spinal trigeminal nuclear complex is an essential relay nucleus in the anatomic substrate subserving the conduction and integration of impulses evoked by noxious stimuli. I t follows tha t a thorough knowledge of the routes and terminals of afferent pathways extending from nucleus caudalis is necessary to the understanding of neural mechanisms involved in clinically recognized pat terns of pain. Anatomic studies 7,32,33 indicate tha t the pat tern of axonal trajectories emanating from nucleus caudalis differs from tha t of the more rostral components of the spinal trigeminal nuclear complex (nucleus interpolaris and nucleus oralis) and the main sensory nucleus. Furthermore, the soma of trigeminal fibers which project directly to the midbrain and thalamic centers associated with nociperception are contained only within nucleus caudalis. This report presents the findings of an electrophysiologic s tudy devised to identify midbrain and thalamic loci activated by a trigeminal input relayed primarily through nucleus caudalis and to compare these regions with brain-stem loci act ivated by impulses relayed at all levels of the trigeminal nuclear complex. The results of this investi-