Striated anal sphincter denervation in patients with progressive supranuclear palsy.

Anal sphincter electromyography may contribute to the differential diagnosis between Parkinson's disease (PD) and other parkinsonisms featuring autonomic dysfunction, such as multiple system atrophy (MSA). Although patients with progressive supranuclear palsy (PSP) do not normally exhibit clinical signs of autonomic dysfunction, a few may be first seen with urinary and fecal incontinence. We performed an electromyographic study of the anal sphincter in 12 patients with clinical criteria of probable or definite PSP, two of them with clinical manifestations of vesical and anal sphincter dysfunction. The results have been compared with those obtained from six patients with PD and six patients with MSA. An abnormal anal sphincter examination was present in five of 12 PSP patients (41.6%). The abnormal motor units of these patients were indistinguishable from those observed in patients with MSA. Patients with MSA had the largest, and patients with PD had the lowest, proportion of abnormal motor units. We conclude that some patients with PSP may have electromyographic signs of denervation in the anal sphincter, which make them indistinguishable by using this test alone from patients with MSA.