Perineal nerve stimulation for urinary sphincter control. Experimental study.

The effect of electrostimulation of the perineal nerve on the external urethral sphincter (EUS) and urethral pressure was studied in 9 dogs. The nerve was displayed in the ischiorectal fossa through a para-anal incision and an electrode was applied to it. Perineal nerve stimulation effected an increase of the urethral pressure (P < 0.01) and EMG activity of the EUS (P < 0.01), but not of the vesical pressure (P > 0.05). The greater the stimulus frequency, the higher the rise of the urethral pressure and EUS activity up to 50 Hz beyond which no further increase occurred. The duration of response diminished with increased frequency, the shortest being at 80 Hz (P < 0.001). The latency of the response decreased with increased stimulus frequency (P < 0.05). In terms of force and speed of contraction, stimulus frequency of 50 Hz evokes the most adequate EUS contraction. An off-time of double the stimulation phase allows indefinite re-stimulation. Chronic electrostimulation of the perineal nerve may restore the sphincter tone so that perineal stimulation could be dispensed with.