Intraoperative neuromonitoring in rectal cancer surgery: a systematic review and meta-analysis

Intraoperative pelvic neuromonitoring based on bioimpedance signals: a new method analyzed on 30 patients

PURPOSE

Increasing importance has been attributed in recent years to the preservation of the pelvic autonomic nerves during rectal resection to achieve better functional results. In addition to improved surgical techniques, intraoperative neuromonitoring may be useful.

METHODS

This single-arm prospective study included 30 patients who underwent rectal resection performed with intraoperative neuromonitoring by recording the change in the tissue impedance of the urinary bladder and rectum after stimulation of the pelvic autonomic nerves. The International Prostate Symptom Score, the post-void residual urine volume and the Low Anterior Resection Syndrome Score (LARS score) were assessed during the 12-month follow-up period.

RESULTS

A stimulation-induced change in tissue impedance was observed in 28/30 patients (93.3%). In the presence of risk factors such as low anastomosis, neoadjuvant radiotherapy and a deviation stoma, an average increase of the LARS score by 9 points was observed 12 months after surgery (p = 0,04). The function of the urinary bladder remained unaffected in the first week (p = 0,7) as well as 12 months after the procedure (p = 0,93).

CONCLUSION

The clinical feasibility of the new method for pelvic intraoperative neuromonitoring could be verified. The benefits of intraoperative pelvic neuromonitoring were particularly evident in difficult intraoperative situations with challenging visualization of the pelvic nerves.

Utility of Intraoperative Neuromonitoring to Protect against Adjacent Nerve Injury in Musculoskeletal and Lymph Nodal Cryoablation

PURPOSE

To demonstrate the utility of intraoperative neuromonitoring (IONM) as an effective method of passive thermoprotection against cryogenic injury to neural structures during musculoskeletal and lymph node cryoablation.

MATERIAL AND METHODS

Twenty-nine patients (16 men; mean age among men, 68.6 years [range, 45-90 years]; mean age among women, 62.6 years [range, 28-88 years]) underwent 33 cryoablations of musculoskeletal and lymph node lesions. Transcranial electrical motor-evoked potentials (MEPs) and somatosensory-evoked potentials (SSEPs) of target nerves were recorded throughout the ablations. Significant change was defined as waveform amplitude reduction greater than 30% (MEP) and 50% (SSEP). The primary outcomes of this study were immediate postprocedural neurologic deficits and frequency of significant MEP and SSEP amplitude reductions.

RESULTS

Significant amplitude reductions were detected in 54.5% (18/33) of MEP tracings and 0% (0/33) of SSEP tracings. Following each occurrence of significant amplitude reductions, freeze cycles were promptly terminated. Intraprocedurally, 13 patients had full recovery of amplitudes to baseline, 11 of whom had additional freeze cycles completed. In 5 of 33 (15.2%) cryoablations, there were immediate postprocedural neurologic deficits (moderate adverse events). Unrecovered MEPs conferred a relative risk for neurologic sequela of 23.2 (95% CI, 3.22-167.21; P < .001) versus those with recovered MEPs. All 5 patients had complete neurologic recovery by 12 months.

CONCLUSIONS

IONM (with MEP but not SSEP) is a reliable and safe method of passive thermoprotection of neurologic structures during cryoablation. It provides early detection of changes in nerve conduction, which when addressed quickly, may result in complete restoration of MEP signals within the procedure and minimize risk of cryogenic neural injury.

Pelvic Intraoperative Neuromonitoring Prevents Dysfunction in Patients With Rectal Cancer: Results From a Multicenter, Randomized, Controlled Clinical Trial of a NEUROmonitoring System (NEUROS)

OBJECTIVE

This NEUROmonitoring System (NEUROS) trial assessed whether pelvic intraoperative neuromonitoring (pIONM) could improve urogenital and ano-(neo-)rectal functional outcomes in patients who underwent total mesorectal excisions (TMEs) for rectal cancer.

BACKGROUND

High-level evidence from clinical trials is required to clarify the benefits of pIONM.

METHODS

NEUROS was a 2-arm, randomized, controlled, multicenter clinical trial that included 189 patients with rectal cancer who underwent TMEs at 8 centers, from February 2013 to January 2017. TMEs were performed with pIONM (n=90) or without it (control, n=99). The groups were stratified according to neoadjuvant chemoradiotherapy and sex, with blocks of variable length. Data were analyzed according to a modified intention-to-treat protocol. The primary endpoint was a urinary function at 12 months after surgery, assessed with the International Prostate Symptom Score, a patient-reported outcome measure. Deterioration was defined as an increase of at least 5 points from the preoperative score. Secondary endpoints were sexual and anorectal functional outcomes, safety, and TME quality.

RESULTS

The intention-to-treat analysis included 171 patients. Marked urinary deterioration occurred in 22/171 (13%) patients, with significantly different incidence between groups (pIONM: n=6/82, 8%; control: n=16/89, 19%; 95% confidence interval, 12.4-94.4; P =0.0382). pIONM was associated with better sexual and ano-(neo)rectal function. At least 1 serious adverse event occurred in 36/88 (41%) in the pIONM group and 53/99 (54%) in the control group, none associated with the study treatment. The groups had similar TME quality, surgery times, intraoperative complication incidence, and postoperative mortality.

CONCLUSION

pIONM is safe and has the potential to improve functional outcomes in rectal cancer patients undergoing TME.

Effect of Neoadjuvant Therapy on the Functional Outcome of Patients With Rectal Cancer: A Systematic Review and Meta-Analysis

AIMS

The impact of neoadjuvant therapy on the functional outcome of patients with resectable rectal cancer is still controversial. The aim of the present study was to explore the effects of neoadjuvant therapy on anorectal function (ARF), urinary function and sexual function in relevant patients.

MATERIALS AND METHODS

PubMed, Embase, Web of Science and the Cochrane Library were searched systematically. All English-language studies, published from January 2000 to July 2021, that explored the (postoperative) effects of neoadjuvant therapy versus upfront surgery on ARF, urinary function and sexual function of patients were included (PROSPERO 2021: CRD42021281617).

RESULTS

The data in this study were derived from 37 articles based on 33 studies; in total, 17 917 patients were enrolled. The meta-analysis revealed that the incidence of anorectal dysfunction in the neoadjuvant therapy group was significantly higher than that in the group of upfront surgery, which was manifested by a higher incidence of major low anterior resection syndrome (odds ratio = 3.09, 95% confidence interval = 2.48, 3.84; P < 0.001), reduction of mean squeeze pressure and mean resting pressure, and other manifestations, including clustering of stools, incontinence, urgency and use of pads. With the extension of follow-up time, the adverse effects of neoadjuvant therapy on major low anterior resection syndrome existed. Compared with patients undergoing upfront surgery, neoadjuvant therapy increased the risk of urinary incontinence (odds ratio = 1.31, 95% confidence interval = 1.00, 1.72; P = 0.05) and erectile dysfunction (odds ratio = 1.77, 95% confidence interval = 1.27, 2.45; P < 0.001).

CONCLUSION

Compared with upfront surgery, neoadjuvant therapy is not only associated with impairment of ARF, but also with increased incidence of urinary incontinence and male erectile dysfunction. However, the influence of confounding factors (e.g. surgical method, tumour stage) needs to be considered.