Shy-Drager syndrome: neuronal loss depends on size, function, and topography in ventral spinal outflow.

We analyzed myelinated fibers and neurocytons in the ventral spinal outflow of patients with Shy-Drager syndrome. Axonal loss occurred predominantly in thin, myelinated fibers that correspond mainly to autonomic preganglionic axons. Intermediate and large myelinated fibers, mainly gamma and alpha axons, were also involved, but to a lesser degree. Neuronal and axonal loss was more prominent in caudal segments and less in rostral segments. Axonal degeneration in single teased fibers was seen frequently in ventral spinal roots.