The splanchnic autonomic outflow in Shy-Drager syndrome and idiopathic orthostatic hypotension.

Since splanchnic outflow is important in the maintenance of postural normotension in man, we performed a quantitative analysis of preganglionic autonomic neuron cell bodies of the seventh thoracic spinal cord segment and their corresponding axons in 2 patients with Shy-Drager syndrome (SDS) and 1 with idiopathic orthostatic hypotension (IOH) and compared these values to control data. The intermediolateral column (ILC) neuron cell body counts were reduced to 17% of control levels in SDS and 52% of control levels in IOH. The B fiber counts in the corresponding ventral spinal root were reduced to 21% and 41% in SDS and IOH, respectively. From the present study and our previous results of ILC counts with age, we infer that orthostatic hypotension does not develop until half or more of the preganglionic autonomic neurons have degenerated. An additional finding in SDS is that there is involvement beyond autonomic neurons.