Cell changes in sensory ganglia following proximal and disal nerve section in the monkey

Abstract Ganglion cell changes were studied in 25 monkeys following systematic section of spinal and cranial sensory nerves proximal or distal to the ganglion. Ganglion cells were studied in Nissl preparations while central degeneration was studied in Nauta‐Gygax stained sections. Morphological characteristics of normal ganglia were studied in unoperated controls. In normal ganglia three categories of cells were identified: (1) A predominant largecelled group (ranging from 20 to 100 μ), (2) small dark cells, and (3) a small number of “atypical” cells. Division of nerves proximal to ganglia produced no cellular changes in most cases; changes attributed to relative ischemia occurred in a few ganglia. Centrally projecting fibers of sectioned nerves were degenerated. Division of sensory nerves distal to ganglia produced profuse chromatolytic changes in cells of all sizes and types within ganglia but no central degeneration. Cervical section of the vagus produced chromatolytic cell changes in the inferior ganglion and a small portion of the superior ganglion unrelated to the auricular nerve. Section of the facial nerve distal to the geniculate ganglion produced chromatolysis in approximately half of the ganglion cells. An accessory trigeminal ganglion, composed of cells of autonomic type, was found distal to the trigeminal ganglion in association with the third division of the nerve. Severance of nerve fibers distal to sensory ganglia eliminates peripheral neurotrophic influences necessary for the growth and maintenance of the ganglion cell. It is postulated that the integrity of this influence is sufficient to sustain sensory ganglion cells after their central processes have been sectioned.