Function of the anal sphincters in spinal man.
Eight patients with traumatic transverse lesions of the spinal cord and eight healthy controls were examined with respect to the function of the anal sphincters. Continuous recordings of anal pressure and electromyograms from the striated sphincter muscles were obtained during gradual rectal distension by means of an air-filled balloon. The patients were more prone than the controls to display a cessation of all electrical activity from the striated muscles in response to rectal distension and they also exhibited a less pronounced inflation reflex. It is concluded that upon rectal distension in normal man the striated muscles are stimulated by a cerebral centre at an unconscious level as well as by a low centre of the spinal cord. The former accounts for an augmented inflation reflex and maintained or increased electrical activity when rectal distension is substantial. The smooth internal sphincter was found to be independent of cerebral influence at rest as well as during rectal distension.