Cavernoso-Anal Reflex. the Description of a Reflex and Its Clinical Significance

Abstract

The cavernoso-anal reflex was described in 17 healthy volunteers of whom 10 were men and 7 women (mean age 38.3 years). The electromyographic (EMG) response of the external (EAS) and internal (IAS) anal sphincters to ischio- and bulbo-cavernosus muscle stimulation was recorded. This was performed through insertion of a needle electrode into each of the 2 cavernosus muscles (stimulating electrode) and the 2 anal sphincters (recording electrode). The test was repeated once after anesthetizing the 2 anal sphincters and a second time after anesthetizing the 2 cavernosus muscles. The EAS and IAS contracted upon stimulation of each of the cavernosus muscles but did not respond to stimulation of the anesthetized muscles. The mean latency for the EAS was 33.8 ms and for the IAS 27.4 ms. During the sexual act, EAS contraction upon cavernosus muscle contraction evokes the ano-urethral reflex with a resulting EUS contraction. The latter closes the vesical neck and prevents retrograde ejaculation in men and urine leak in both sexes. Meanwhile, the role of anal sphincter contraction during the sexual act is unknown. However, the cavernoso-anal reflex could be included as a diagnostic tool in the diagnosis of neurologic and sexual disorders, in particular erectile dysfunction. Detectable changes in latency of the reflex or in motor unit action potentials would indicate nerve or muscle damage. This reflex seems to be more constant than the bulbo-cavernosus reflex and could replace it with respect to diagnosis of the afore-mentioned disorders.