Neuromonitoring predicts functional outcome after rectal cancer surgery

Mar 6 2013

Intraoperative neuromonitoring (IONM) of the bladder and internal anal sphincter can accurately predict postsurgical urinary and anorectal function, research suggests.

The authors say the technique could increase knowledge of nerve topography, improve nerve-sparing surgery, and enhance postoperative outcomes.

"It may provide new insights into the intraoperative pelvic neuroanatomical topography and help to answer the question where, how, and why autonomic nerve damage occurs," say Werner Kneist (University of Mainz, Germany) and colleagues.

The study included 35 patients undergoing low anterior resection. The researchers performed IONM through stimulation of the pelvic splanchnic nerves during and after surgery with simultaneous electromyography (EMG)-based monitoring of internal anal sphincter innervation and bladder manometry.

Of the 33 patients who underwent bladder manometry, five reported deterioration of urinary function requiring long-term catheterization. All of these patients had negative IONM results under manometry. There was also one false-positive result for urinary dysfunction using bladder manometry.

And, among 26 patients in whom anorectal function was assessed using IONM, two experienced severe postoperative deterioration. Both of these patients had negative results under EMG of the internal anal sphincter, and there was one false-positive result using this method.

IONM under bladder manometry was able to predict urinary function with a sensitivity of 100%, a specificity of 96%, and an accuracy of 97%. Meanwhile, IONM under EMG could predict anorectal function with a sensitivity of 100%, a specificity of 96%, and an accuracy of 96%.

However, IONM under bladder manometry was a poorer predictor of anorectal function than EMG of the internal anal sphincter, which in turn was a poorer predictor of urinary function than bladder manometry. This suggests that "none of the measurements is equally valid for both functions," say the authors.

Writing in the International Journal of Colorectal Disease, Kneist and colleagues say that the technique could be used in nerve-sparing surgery for both primary and secondary prevention.

"The presented IONM method enables identification of macroscopically unrecognized neural tissue during surgery in the small pelvis and could be used for nerve-sparing guidance as a tool for primary prevention," they write.

"The predictability of postoperative urinary and neurogenic anorectal dysfunctions could serve as a secondary prevention with early initiation of urologic and proctological treatments with the potential for improvement in prognosis."

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