Noradrenaline response to edrophonium in primary autonomic failure: distinction between central and peripheral damage

The effects of intravenous edrophonium on plasma noradrenaline were studied in 12 subjects with primary autonomic failure. 5 had clinical features of central autonomic damage, 4 with parkinsonism (PD) and 1 with multiple system atrophy (MSA); the other 7 had clinical features of progressive autonomic failure without detectable central neurological damage (PAF). After edrophonium all but 1 subject showed falls in heart rate of about 6 beats/min; there were no consistent blood pressure changes. The 5 PD/MSA patients all had normal plasma noradrenaline responses to edrophonium, with rises of 35-66% within 2-8 min of injection. 6 of the 7 PAF patients had no response or very small responses (-6 to +11%), while the other subject had a normal response (70% rise). The noradrenaline response to edrophonium may provide a simple way to differentiate between central and peripheral autonomic damage.