Chronic neurogenic lesions of the external anal sphincter and abdomino-pelvic dyssynergia in chronic constipation.

Background. Neuropathy of the pudendal nerves which may be found in constipated patients has been considered the result of pelvic floor descent due to the repetitive acts of straining at stool. However the relationship between abdominopelvic dyssynergia, which may lend to repetitive acts of straining and neurophysiopathologic alterations of the pelvic floor has not yet been fully elucidated. Aim of this study was to assess the relationship between neurophysiologic alterations of the external anal sphincter; patterns of altered evacuation and defaecographic pelvic floor physiology in 32 patients with chronic idiopathic constipation. Results. Ar electromyography partial muscle denervation, identified as chronic neurogenic lesions of the external anal sphincter were found in 19% and dyssynergia (co-contraction of external anal sphincter and abdominal muscles) in 34% of the investigated subjects. Patients with different electromyography patterns did not differ as far as concerns symptoms of altered evacuation, bowel frequency, use of digital manoeuvres, age, and duration of symptoms. The presence of neurophysiologic alterations was significantly associated with altered defaecographic findings: reduced ano-rectal angle at rest in chronic neurogenic lesions and abdomino-pelvic dyssynergia (p<0.01); excessive pelvic floor descent in the presence of chronic neurogenic lesions (p<0.05). Conclusions. In chronically constipated patients symptoms of altered defaecation do not appear to be related to abdomino-pelvic dyssynergia and/or chronic neurogenic lesion of the external anal sphincter and do not show any association with defaecographic alterations. These results suggest that straining at. evacuation can be induced by additional factors other than abdomino-pelvic dyssynergia and chronic neurogenic lesions and that these two alterations have different pathogenetic mechanisms.