Sphincteric events during penile vibratory ejaculation and electroejaculation in men with spinal cord injuries

Purpose: We investigate internal and external sphincter responses during pe nile vibratory stimulation and electroejaculation in men with spinal cord i njury. Materials and Methods: Ejaculation induction with simultaneous recording of external and internal sphincter pressures was performed in 9 spinal cord i njured men. Of the patients with upper motor neuron lesions 3 underwent pen ile vibratory stimulation and 3 underwent electroejaculation. In 3 men who did not respond to PVS, including 1 with upper motor neuron and 2 with lowe r motor neuron lesions, penile vibratory stimulation and subsequent electro ejaculation were performed. Results: In successful penile vibratory stimulation and electroejaculation upper motor neuron cases external sphincter pressure first reached a peak ( average 180 cm. H2O) and subsequently decrease followed in 3 to 10 seconds by a peak in internal sphincter pressure (average 178 cm. H2O), which excee ded external sphincter pressure and ejaculation occurred. During electroeja culation, the pattern progressed, despite complete discontinuation of elect rical stimulation. In electroejaculation, there was a trend for a more rapi d return of external sphincter pressure greater than internal sphincter pre ssure, which may explain the electroejaculation retrograde fraction. In non responders external sphincter pressure never increased to more than 105 cm. H2O in response to penile vibratory stimulation and no ejaculation was ind uced. In nonresponders to penile vibratory stimulation, electroejaculation induced a typical sustained increase in internal sphincter pressure and ext ernal sphincter pressure but at lower peak pressures. Conclusions: Forceful contraction of the external sphincter followed by con traction of the internal sphincter always precedes ejaculation during elect roejaculation and penile vibratory stimulation. Similarities between penile vibratory stimulation and electroejaculation suggest that the latter induc es ejaculation via a complex neurological pathway rather than by simple dir ect end organ stimulation. The sustained nature of the response to electroe jaculation suggests that electrical stimulation should be stopped completel y during ejaculation to allow more relaxation of the external sphincter, as this may lead to a decrease in the retrograde fraction.