Assessment of penile small nerve fiber damage after transurethral resection of the prostate by measurement of penile thermal sensation.

Objective: To determine the occurrence of penile small nerve fiber damage following transurethral resection of the prostate (TURP) for benign prostatic hypertrophy (BPH).

Methods: Penile nerve function was evaluated in 18 consecutive patients prior to and one month after TURP for BPH. To test nerve fibers of small diameter, the penile warm and cold sensory thresholds were measured by means of a Peltier-based device, as well as the penile sympathetic skin potentials obtained following electrical stimulation at the wrist. To test nerve fibers of large diameter, the pudendal nerve somatosensory evoked potentials (pSEPs) and the penile vibratory thresholds were recorded. Clinical erectile function was quantified using a standardized questionnaire (erectile dysfunction symptom score, EDSS). Urinary handicap was assessed by the measurement of maximum flow rate (MFR) at uroflowmetry and by a standardized questionnaire (AUA symptom score, AUASS).

Results: Penile warm threshold (+7.8 vs +6.3C, p = 0.005), cold threshold (-8.5 vs -5.7C, p = 0.003) and vibratory threshold (9.3 vs 7.9 microm., p = 0.03) were significantly higher after than prior to TURP. The amplitude of pSEPs tended to decrease (1.7 versus 2.3 microV, p = 0.06), whereas the remaining neurophysiological parameters were unchanged. Clinical assessment by EDSS demonstrated a significant postoperative erectile function impairment (20.2 vs 17.5, p = 0.04), whereas mictional function improved (MFR: 19 vs 8.8 ml./s and AUASS: 4.9 versus 15.1, p < 0.0001).

Conclusions: This study highlights the occurrence of penile small nerve fiber damage following TURP and supports the hypothesis of neurogenic damage as the primary cause of post-operative erectile dysfunction.