The anal reflex in idiopathic faecal incontinence: an electrophysiological study.

We have recorded the latency of the anal reflex, using a simple electrophysiological method, in 22 patients with anorectal incontinence and in 33 control subjects without anorectal disease. The mean latency in the control subjects was 8.3 ms (range 5-11.3 ms). In the patients with faecal incontinence the mean latency of the anal reflex was 13.0 ms (range 6.5-22.0 ms). The reflex latency was within the normal range in only three incontinent patients. These findings support our concept, based on histological examination of the external anal sphincter musculature, that a major cause of this syndrome is denervation of these muscles due to damage to the innervation of the external anal sphincter and puborectalis muscles.