Electrophysiological evaluation of genito-sphincteric dysfunction in multiple system atrophy.

Thirteen patients with multiple system atrophy underwent multimodality neurophysiological evaluation, including sphincteric needle electromyography (EMG), sacral reflexes, pudendal nerve terminal latency, pudendal (PSEPs) and tibialis posterior nerve somatosensory evoked potentials (TPSEPs), and perineal motor evoked potentials (PMEPs). EMG revealed denervation or neurogenic changes, with reduction in spontaneous tonic activity at rest and abnormal pudendal nerve terminal latency in 10 patients (76.9%); anal reflex was delayed in 7 patients (53.8%). TPSEPs scalp responses were clearly abnormal in 4 patients (30.7%), whereas PSEPs exhibited changes in 9 (69.2%): in 6 patients responses were delayed at lumbar level (46.2%), and in 5 over the scalp (38.4%). PMEPs showed an increase in latency with a mild prolongation of central motor conduction time (CMCT) in 2 cases (15.3%); 1 patient had prolonged latencies following both cortical and sacral stimulation, but a normal CMCT. Even if diagnostic yield is not improved using these investigations they provide evidence of multiple lesion sites other than Onuf's nucleus.