Investigation of the effects of radical prostatectomy operation on cavernosal smooth muscle by corpus cavernosum electromyography

Erectile dysfunction is one of the most important complications after radical prostatectomy. Cavernous nerve is the main autonomic nerve supply of the penis and injury of this nerve is predominant cause of post-radical prostatectomy erectile dysfunction. Losing the autonomic support of the penis due to cavernous nerve injury leads to apoptosis and increased oxidative stress, and consequently a decrease in the smooth muscle/collagen ratio in cavernous tissues, which ruins the erection mechanism. Corpus cavernosum electromyography is a non-invasive test that provides information about penile autonomic innervation and cavernous smooth muscle function. Our aim was to evaluate the changes in corpus cavernosum electromyography caused by radical prostatectomy with respect to bilateral nerve sparing, unilateral nerve sparing, and non-nerve-sparing status. Furthermore, to understand the clinical reflection of these changes in terms of erectile function. Forty-four patients included in this study who underwent radical prostatectomy due to prostate cancer. The patients were divided into 3 groups as bilateral nerve preservation (n = 21), unilateral nerve preservation (n = 12), and non-nerve preservation (n = 11) during radical prostatectomy. Corpus cavernosum electromyography was applied to all of the patients both before and 3 months after radical prostatectomy. During the corpus cavernosum electromyography recording, 60 mg papaverine was injected into the corpus cavernosum in order to induce erection. The amplitude values of the electromyography waves were recorded both before and after the papaverine injection. The relaxation degree, which is defined as the percentage decrease in the amplitude of cavernous electrical activity after intracavernous papaverine injection was also calculated. The patients were also questioned with the International Index of Erectile Function (IIEF)-5 form before, 3, and 12 months after the surgery. There was no significant difference between groups in terms of corpus cavernosum electromyography results and IIEF-5 scores before surgery (p > 0.05). However, at the 3rd-month corpus cavernosum electromyography, the relaxation degree of cavernous smooth muscle was significantly higher in patients have bilateral nerve preservation when compared within patients those having unilateral and non-nerve preservation (p = 0.010 and p = 0.032, respectively), while there was no significant difference between patients in unilateral nerve preservation and non-nerve preservation (p > 0.05). The 3rd and 12th month IIEF-5 scores of the patients who underwent bilateral nerve preservation were significantly higher than the other 2 groups (p = 0.004 and p < 0.001, respectively). The regression analysis showed that the relaxation degree at the 3rd-month corpus cavernosum electromyography predicted the IIEF-5 score at the 12th month postoperatively, regardless of nerve-sparing status (p = 0.034). In conclusion, corpus cavernosum electromyography performed in the early period after radical prostatectomy has predictive value for the long-term erectile functions of the patients. Corpus cavernosum electromyography is an easy-to-apply and non-invasive test, and it has a high potential to have an important role in the clinical management of patients after radical prostatectomy.