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Electromyographic analysis of the effects of robotic-assisted and retropubic radical prostatectomy on cavernous nerves and smooth muscles

Year: 2025
Type: article
Abstract: Dissection, coagulation, and retraction during radical prostatectomy (RP) can lead to ischemia, inflammation, and oxygenation disturbances, negatively affecting cavernous nerve function. Nerve injury may trigger fibrosis and apoptosis in the corpora cavernosa, resulting in postoperative erectile dysfunction (ED).1 Due to methodological diversity and uncertainties in signal accuracy, postoperative neurophysiological evaluation of cavernous nerves has not been fully integrated into clinical practice. This study investigates whether corpus cavernosum electromyography (CC-EMG) can objectively assess the electrical function of cavernous nerves and smooth muscle function in the postoperative period. This will provide a better understanding of CC-EMG’s effectiveness and usability in managing postoperative ED and contribute to the development of surgical techniques and penile rehabilitation protocols. In this prospective cohort study conducted between 2022 and 2024, radical prostatectomy was performed using the robotic-assisted radical prostatectomy (RARP) method in 26 patients and the retropubic radical prostatectomy (RRP) method in 22. All cases underwent the International Index of Erectile Function (IIEF) 5/15 questionnaire and CC-EMG tests approximately 2 weeks before surgery and at the third and sixth postoperative months. Patients with ED, Peyronie’s disease, penile deformities, diabetes, androgen deficiency, neurological disorders affecting erectile function, or a history of pelvic/penile surgery or radiotherapy were excluded. After informing patients about the operation, informed consent was obtained. Operative time was recorded from the first incision to the last suture, separately for each group, for comparative analysis. Blood loss was measured based on aspirator reservoir contents and sponges used during surgery. In the postoperative period, phosphodiesterase-5 inhibitors, intracavernosal injection therapy, and vacuum therapy were offered for penile rehabilitation. The study was approved by the local ethics committee, and all patients provided written informed consent, in accordance with the Declaration of Helsinki. Corpus cavernosum electromyography measures cavernosal electrical activity (CEA) to assess nerve transmission and smooth muscle function, aiding in sexual function monitoring and new treatment development. Participants were instructed to avoid alcohol, cigarettes, coffee, and sexual activity 24 hours before measurements. After explaining the procedure, informed consent was obtained. The electromyography study was conducted in a quiet, dimly lit room (22-24°C) with the patient supine, wearing comfortable clothing, between 09:00 and 12:00. Blood pressure and pulse were measured beforehand, and recordings began after 15 minutes of rest. Cavernosal electrical activity of the penis was measured using a high-speed electromyography module (Medical Measurement Systems, Enschede, The Netherlands). Recordings were taken while the patient was relaxed. To avoid interference from sympathetic nerve potentials, coaxial needle electrodes (20 mm, 0.4 mm diameter, gold-plated, VIASYS Healthcare, Madison, WI, USA) were used. A ground electrode was placed on the leg, and a 200 Hz sampling frequency with a 0.1-20 Hz bandpass filter was applied. After 20 minutes of CEA recordings, cavernous nerve electrical potentials were analyzed by marking peak-to-peak amplitudes. If no change was observed, papaverine hydrochloride (60 mg) was injected into one corpus cavernosum. The degree of smooth muscle relaxation, indicated by suppressed electrical amplitudes, was measured, allowing for the evaluation of cavernous smooth muscle relaxation, neurogenic electrodysfunction, and cavernous nerve integrity (Figure S1). In this study, SPSS 22.0 was used for statistical analysis. Numerical variables are given as mean and median, categorical variables as percentages (%). Electrophysiological parameters were evaluated preoperatively and postoperatively. The Mann-Whitney U and Wilcoxon Signed-Rank tests were used for categorical or ordinal data, and the Shapiro-Wilk test assessed variable distribution. A P-value <.05 was considered statistically significant. A total of 48 patients were included. The groups showed no significant differences in pathological stage, nerve sparing radical prostatectomy (NS-RP) status, or comorbidities. Table S1 presents the demographic and clinical characteristics. Cavernous electrical potential amplitudes and cavernous smooth muscle relaxation degrees were compared using CC-EMG. Additionally, changes in IIEF-5 scores were also evaluated. Nerves were preserved unilaterally in 2 RARP and 3 RRP patients. The RARP nerve-sparing group showed significantly higher cavernous electrical amplitudes, smooth muscle relaxation, and IIEF-5 scores than non–nerve-sparing patients and the RRP group (Table S2). Postoperative erectile function improved faster in nerve-sparing patients, while non–nerve-sparing cases showed limited recovery and greater erectile function loss. A postoperative IIEF-5 score increase of ≥5 points was considered successful. Phosphodiesterase-5 inhibitors, intracavernous injections, and vacuum therapy were suggested for penile rehabilitation. These findings highlight the importance of RARP and nerve preservation for postoperative cavernous nerve integrity and smooth muscle function. They also suggest CC-EMG as a potential tool alongside IIEF for monitoring erectile function and developing penile rehabilitation strategies. Erectile dysfunction is a common complication after RP and can occurs at around 60% even with RARP, which provides better visualization.2 Cavernous nerve injury reduces nitric oxide levels and increases oxidative stress, triggering smooth muscle apoptosis, collagen accumulation, and fibrosis, leading to veno-occlusive dysfunction and ED.3 Corpus cavernosum electromyography is believed to provide more objective evidence of cavernous nerve integrity compared to subjective tests. Yıldız et al. evaluated changes in penile sensation using electrophysiological tests in 26 patients who underwent radical prostatectomy and reported that cavernous and dorsal penile nerve injury could lead to sensory loss associated with postoperative ED.1 Cavernosal electrical activity measured by CC-EMG originates from the membrane potentials of cavernous smooth muscle cells innervated by autonomic nerves. Cavernous nerve injury may reduce the amplitude and coordination of corpus cavernosum potentials and impair smooth muscle relaxation. This can be attributed to autonomic innervation loss due to cavernous nerve damage and degeneration caused by the loss of gap junctions. With better nerve protection during surgery, the amplitude of cavernous electrical potentials and smooth muscle relaxation levels can be better preserved.4 This study is the first to compare the effects of RARP and RRP on postoperative CC-EMG. As expected, the non–nerve-sparing technique led to a significant decrease in CC-EMG potentials and cavernous smooth muscle relaxation due to reduced autonomic innervation of the cavernous tissue. This decrease was similar in both RARP and RRP groups. However, cavernous potentials were significantly higher in RARP than in RRP, despite a notable reduction from preoperative levels. Despite nerve-sparing, the decrease in cavernous potentials indicates partial cavernous nerve damage. Furthermore, these changes correlate with IIEF scores. In patients who underwent NS-RP, cavernous potentials were higher in the RARP group, with a statistically significant difference. After intracavernous vasodilator injection, cavernous smooth muscle relaxation was significantly higher in the robotic and nerve-sparing surgery groups. These findings suggest that varying degrees of cavernous nerve damage may occur during radical prostatectomy, regardless of the technique used. Nerve-sparing surgery and RARP are more effective in preserving cavernous nerves and postoperative erectile function. Corpus cavernosum electromyography provides more objective information than subjective tests like IIEF-5 in evaluating cavernous nerve integrity and erectile function postoperatively, making it valuable for patient follow-up. The limitations of the study include a small sample size, a relatively short follow-up period, and non-standardized electrophysiological devices. Larger and longer-term studies are needed for long-term outcomes. Reductions in cavernous electrical potential amplitudes and smooth muscle relaxation in CC-EMG are indicators of cavernous nerve damage and postoperative ED. These results suggest that RARP offers greater precision in preserving nerves and maintaining postoperative cavernous nerve and smooth muscle function. Nerve protection strategies play a crucial role in postoperative recovery, with the RARP being superior in this aspect. The use of electrophysiological tests in postoperative follow-up could enable more effective treatment planning and better management of the recovery process. None. All authors contributed to the article. F.A. was responsible for designing and review the study protocol, writing the protocol and manuscript, conducting the study, screening potentially eligible studies, extracting and analyzing data, interpreting results, updating reference lists, and creating “Summary of findings” tables. Ö.K. contributed to the design of the review protocol, writing the report, arbitrating potentially eligible studies, extracting and analyzing data, and interpreting results. In addition, contributed to data extraction and provided feedback on the report. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. The authors declare that they have no conflict of interest.
DOI: 10.1093/jsxmed/qdaf101
Language: English
Field: Medicine
Open Access status: hybrid
Estimated APC paid: $3,550
OpenAlex ID: W4410693379
FWCI:
Cites: 5
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Related to: 10