Disturbances of ano-rectal function in multiple sclerosis

Thirty patients with multiple sclerosis (MS) [18 men and 12 women, mean age 40 years (range 22-50), disease duration 12 years (range 0.5-34), Kurtzke's Expanded Disability Status Score 6.0 (range 4.0-7.5)] were interviewed about bowel symptoms and studied using ano-rectal manometry. The results were compared with findings in healthy controls. Twenty-eight had bowel symptoms: 8 constipation, 10 constipation and infrequent faecal urgency, 4 infrequent faecal incontinence and 6 frequent faecal incontinence. Anal sphincter pressure at rest was significantly reduced in MS patients 69 (SD 17) cm H2O, compared with 92 (SD 15) cm H2O in controls, and the external sphincter contraction force was also significantly reduced. Rectal sensation and rectal compliance were reduced and the ano-rectal inhibition reflex (defaecation reflex) required a higher rectal pressure to be elicited in the patients. Upon rectal filling, an early external sphincter excitation was seen. The presence of faecal incontinence correlated strongly with reduced rectal sensation. The findings suggest that faecal incontinence can at least partly be explained by low anal sphincter pressure and poor rectal sensation. The findings of early sphincter excitation and increased threshold of ano-rectal inhibition reflex may be an important pathophysiological factor for constipation in MS patients.