Nocturnal penile tumescence and effects of complete spinal cord injury: possible physiologic mechanisms.

OBJECTIVES

To determine the role of the spinal cord in the initiation and/or modulation of nocturnal erectile activity, we measured nocturnal penile tumescence (NPT) in men with complete spinal cord injuries at known locations.

METHODS

Eighteen men between the ages of 27 and 57 years (mean 45) with known complete spinal cord lesions and no history of other medical problems adversely affecting erectile function completed International Index of Erectile Function questionnaires and underwent RigiScan testing for two consecutive nights. RigiScan tracings were evaluated for the presence and quality of NPT activity. Erectile episodes lasting longer than 10 minutes with base and tip rigidity greater than 70% were designated "good"; the remainder were designated "borderline," "poor," or "absent."

RESULTS

Of 9 men with cervical injuries and 9 with thoracic injuries, 8 and 3, respectively, had evidence of NPT. Of the 9 men with cervical injuries, 3 had one or more "good" nocturnal erections, and 1 of 9 men with thoracic injuries had one or more "good" nocturnal erections. The mean duration of the single longest erectile event was 26 minutes in men with cervical spinal injuries and 12 minutes in men with thoracic spinal injuries. Men with cervical and thoracic injuries had a mean overall International Index of Erectile Function score of 10 and 16 and a mean erectile domain score of 2 and 3, respectively.

CONCLUSIONS

Spinal regulation is critical for nocturnal erectile activity, and the isolated thoracic cord is less effective than the isolated cervical cord in maintaining NPT. Despite the presence of nocturnal erectile activity, volitional erectile function in spinal cord-injured men is significantly impaired.