Quantitative anal sphincter EMG in multisystem atrophy and 100 controls

Objective-To evaluate data of quantitative anal sphincter EMG in normal con trols and to compare them with patients with multiple system atrophy (MSA). Methods-Quantitative anal sphincter EMG were performed on 100 normal contro ls and 11 patients with MSA to characterise EMG data in these two groups. Results-In the normal controls, there was a trend for increased motor unit potential (MUP) amplitude, duration, area, and polyphasicity with advancing age. Patients with MSA exhibited similar MUP size and fibre density. Signi ficant differences were found only in parameters of the recruitment pattern , which were reduced in MSA, with a diminution in the number of active MUPs during rest. Conclusions-These results may reflect either decreased number of motor cell s in Onuf's nucleus without significant consequential reinnervation, or upp er motor neuron involvement affecting the anal sphincter in MSA. They furth er underline the importance of comparative data for age matched controls.