Comparison of distal sympathetic with vagal function in diabetic neuropathy.

We measured distal sympathetic and vagal function in 73 consecutive patients with diabetic neuropathy seen at the Mayo Autonomic Reflex Laboratory. Postganglionic sympathetic failure measured proximally within the foot occurred as commonly as vagal failure (58% and 55%, respectively) and occurred much more frequently than did orthostatic hypotension (26%). Either vagal or distal sympathetic abnormalities occurred in isolation in about one in six patients with diabetic neuropathy. We conclude that distal sympathetic failure and vagal failure occur with equal frequency when sensitive and quantitative recording methods are used and that it is advantageous to test both systems, as only one may be involved in some patients.