Role of clinical neurophysiological tests in evaluation of erectile dysfunction in people with spinal cord disorders

BACKGROUND: While erectile dysfunction is frequent among people with disorders of the spinal cord, the role of various clinical neurophysiological tests in assessment is not clear.
AIMS: To study the role of clinical neurophysiological investigations in assessing erectile dysfunction among men with spinal cord disorders.
SETTING: National Institute of Mental Health and Neurosciences, India.
DESIGN: Survey.
MATERIALS AND METHODS: Subjects with a score of 21 or less on the International Index of Erectile Function-5 were classified as with erectile dysfunction and with a score of more than 21 as without erectile dysfunction. Clinical neurophysiological studies done were Sympathetic Skin Response from limbs, posterior tibial sensory evoked potential, pudendal sensory potential and bulbocavernous reflex.
STATISTICAL ANALYSES: Chi-square test.
RESULTS: Among 40 subjects 26 had erectile dysfunction. The frequency of abnormalities in clinical neurophysiological studies were: pudendal sensory evoked potentials - 16, posterior tibial sensory evoked potentials - 26, bulbocavernous reflex - 5, sympathetic skin response from sole - 24 and, sympathetic skin response from palm - 18. Significant associations were noted between erectile dysfunction and abnormal pudendal sensory evoked potentials (P=0.0479), and absent sympathetic skin response from palm (P=0.0279) and sole (P<0.001). There was no correlation between erectile dysfunction and posterior tibial sensory evoked potentials (P=0.133) or bulbocavernous reflex (P=0.418). Sympathetic skin response from sole was most sensitive (80.8%) and had best positive (87.5%) and negative predictive (68.8%) values. The specificity of these three tests was 78.6%.
CONCLUSIONS: Sympathetic skin response from the sole of the foot was the most sensitive and specific clinical neurophysiological test for erectile dysfunction in spinal cord disorders.

Keywords
Bulbocavernous reflex, erectile dysfunction, sensory evoked responses, spinal cord injury, sympathetic skin response