DISTRIBUTION OF SUBSTANCE-P IN THE SPINAL-CORD OF PATIENTS WITH SYRINGOMYELIA

The distribution of substance P, a putative neurotransmitter and pain- related peptide, was studied using the peroxidase-antiperoxidase immun ohistochemical method in the spinal cords obtained from autopsy of 10 patients with syringomyelia and 10 age- and sex-matched, neurologicall y normal individuals. Substance P immunoreactivity was present in axon s and in terminal-like processes in close apposition to neurons in the first, second, and third laminae of the dorsal hem. Smaller amounts o f peroxidase-positive staining were found in the fifth lamina of the d orsal hem, the intermediolateral nucleus, the intermediomedial nucleus , and the ventral hem. In nine of 10 patients with syringomyelia, ther e was a substantial increase in substance P immunoreactivity in the fi rst, second, third, and fifth laminae below the level of the lesion. A marked reduction or absence of staining was present in segments of th e spinal cord occupied by the syrinx. Central cavities produced bilate ral abnormalities, whereas eccentric cavities produced changes that we re ipsilateral to the lesion. No alterations in staining were found in the spinal cord of an asymptomatic patient with a small central syrin x. The authors conclude that syringomyelia can be associated with abno rmalities in spinal cord levels of substance P, which may affect the m odulation and perception of pain.