Damage to the innervation of the pelvic floor musculature in chronic constipation.

Constipation and defecation straining have been implicated in the pathogenesis of anorectal incontinence. We have studied 24 women with chronic constipation and 20 age- and parity-matched control subjects. Electrophysiologic techniques were used to study the innervations of the puborectalis and external anal sphincter muscles. The results show that damage can occur to the nerve supply of both these muscles in chronic constipation, and that this probably is due to perineal descent during defecation straining.