Damage to the innervation of the voluntary anal and periurethral sphincter musculature in incontinence: an electrophysiological study.

In 40 women with idiopathic (neurogenic) faecal incontinence, 20 of whom also had stress urinary incontinence, single fibre EMG studies showed an increased fibre density in the external anal sphincter muscle. All these patients showed excessive descent of the pelvic floor on straining. The mean terminal motor latencies in the pudendal and perineal nerves, measured by a digitally-directed intrarectal stimulating technique, were increased when compared with 20 control subjects (p less than 0.01). The perineal nerve terminal motor latency was more markedly increased in the 20 patients with double incontinence than in those with faecal incontinence alone (p less than 0.01). These results provide direct electrophysiological evidence of damage to the innervation of the pelvic floor musculature in idiopathic faecal and double incontinence, and imply that idiopathic stress urinary incontinence may have a similar cause.