The Efficacy of a Nerve Stimulator (Cavermap®) to Enhance Autonomic Nerve Identification and Confirm Nerve Preservation During Total Mesorectal Excision

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Abstract
Sexual dysfunction after total mesorectal excision may be caused by injury to the autonomic nerves. During surgery, nerve identification is not always achieved, and, to date, there has been no method to objectively confirm nerve preservation. The aim of this study was to assess the efficacy of a nerve-stimulating device (CaverMap®) to assist in the intraoperative identification of the autonomic nerves during total mesorectal excision, and objectively confirm nerve preservation after proctectomy is completed. Sexually active consecutive male patients undergoing total mesorectal excision were prospectively enrolled in this study. During pelvic dissection, the surgeon attempted to localize the hypogastric and cavernous nerves. Cavermap® was used to confirm these findings and to facilitate the identification in cases of uncertainty. At the completion of proctectomy, the nerves were restimulated to ensure preservation. Factors that could affect the surgeon's ability to localize the nerves and Cavermap® to confirm this were evaluated. Twenty-nine male patients with a median age of 58 years were enrolled in this study. An attempt to visualize the hypogastric nerves during dissection was made in 26 patients; the surgeon was able to identify the nerves in 19 (73 percent) patients. Cavermap® successfully identified the nerves in six of the seven remaining patients, and failed to identify them in only one case. An attempt to localize the cavernous nerves during dissection was made in 13 patients, of which localization was successful in 8 (61.5 percent) patients. Cavermap® improved the identification rate in four of the remaining five patients. After proctectomy, Cavermap® successfully confirmed the preservation of both hypogastric and cavernous nerves in 27 of 29 (93 percent) patients. A history of previous surgery statistically correlated with failure to identify the hypogastric nerves by the surgeon (P= 0.005). There were no adverse events related to use of the device. Cavermap® may be a useful tool to facilitate identification of the pelvic autonomic nerves during total mesorectal excision and to objectively confirm nerve preservation.