Nocturnal erection detection with the outdated RigiScan is the golden standard for erectile dysfunction (ED) nature differentiation. The Staying Hot and Feeling Hot study have shown that nocturnal erection detection is feasible with patient-friendly overnight penile temperature measurements. The question has arisen whether the penile temperature methodology is also capable to detect the absence of nocturnal erections, which is essential for clinical implementation in erectile dysfunction diagnostics. The objective of the MENDiP-study is to determine the feasibility to detect the absence of nocturnal erections with overnight penile temperature sensors. Furthermore, the MENDiP study functions as a first pilot trial to investigate the effect of age on the penile temperature during nocturnal erections in test subjects with normal erectile functioning. This is done in an observational study with a longitudinal design in which pre- and postoperative ambulatory overnight measurements are performed in patients, aged 55 - 70 years with preoperative normal sexual functioning, undergoing a non- or unilateral nerve-sparing robot assisted radical prostatectomy.

Inclusion Criteria:

1. Preoperative measurement:

   • Aged 55 - 70 years
   • Prostatecancer patients undergoing a non-/unilateral-nerve-sparing radical prostatectomy (RARP)
   • Pre-operative IIEF-5 score > 21

2. Postoperative measurement

   • Inclusion criteria of pre-operative measurement
   • Preoperative penile temperature increase during first nocturnal erection of minimally 0.4 degrees Celsius
   • Post-operative IIEF-5 score < 12 with absence of morning erections

Exclusion Criteria:

• Test subjects who are unwilling to sign informed consent
• Test subjects with erectile dysfunction before RARP (IIEF-5 score of below 22)
• (History of) sickle cell aneamia, atherosclerosis and diabetes type I or II. These conditions might influence penile blood circulation and therefore the accuracy of the study outcomes.
• (History of) REM-sleep behavior disorder or other sleep disorders such as restless legs syndrome, insomnia, and sleep apnea
• Usage of sleeping pills or benzodiazepines.
• Postoperative results will be excluded from the study in case of presence of nocturnal erections according to the RigiScan data.

Fifteen patients, aged 55 - 70 years, who will undergo a non- or unilateral-nerve-sparing robot assisted radical prostatectomy will be included in case preoperative normal erectile functioning and postoperative complete impotence at three months after surgery.