The majority of unmyelinated afferent axons in human ventral roots probably conduct pain

Abstract

Patients [3] with intractable chest pain had undergone dorsal rhizotomy. None had obtained relief, but all 3 had developed dysesthesia and hyperesthesia, in addition to the original pain persisting in the supposedly deafferented area. Dorsal ganglionectomy was performed for these 3 patients in 1976 and they were followed for 3 yr. Following ganglionectomy 2 of the 3 developed total anesthesia, including loss of dysesthesia, hyperesthesia and the original pain. Light microscopical and EM examinations of the ventral roots removed at the time of ganglionectomy showed that unmyelinated axons constituted approximately 25% of the total fiber count. Two ventral roots from 1 patient who previously had serendipitous removal of dorsal ganglia showed a marked reduction in the population of unmyelinated axons. Coggeshall''s contention that the majority of unmyelinated axons in the ventral roots are sensory and probably conduct pain, is supported.