Bulbocavernosus reflex during the micturition cycle in normal male subjects

To investigate normal changes in the bulbocavernosus reflex (BCR) during the micturition cycle, we examined the change in BCR during the micturition cycle using an evoked potential reaction of the BCR (BCR-EP).

Fourteen normal subjects were examined in the study. The BCR-EP was recorded at empty bladder, filled bladder, during voiding and at empty bladder after voiding. To elicit the BCR-EP, the dorsal nerve of the penis was stimulated by two ring electrodes and an electromyogram of the external urethral sphincter was recorded. The maximum amplitude was measured to evaluate changes in the BCR.

The amplitude of the BCR was increased by bladder filling and the ratio of the amplitude at filled bladder/amplitude at empty bladder was 1.32 +/- 0.39. The stable BCR-EP elicited by stimulation at empty bladder disappeared during voluntary voiding in 13 of 14 subjects. However, as stimulation was increased in seven subjects, the BCR-EP was again seen clearly.

The BCR varies during the micturition cycle, although in normal subjects this variation occurs within a relatively narrow range. Changes in the BCR out of the normal range (e.g. large acceleration by bladder filling or insufficient inhibition during voiding) could suggest the existence of neurogenic disease.