The introduction of Total Mesorectal Excision (TME) resulted to the improvement of the
overall survival and local recurrence rates of rectal cancer patients. However, the
associated urogenital and anorectal functional deficit has a significant effect on the
postoperative quality of life of the patient. More specifically, the postoperative rates of
urogenital and sexual dysfunction that have been reported in the various series, are
estimated at the levels of 70% and 90%, respectively. Additionally, TME is associated with
the development of the low anterior syndrome (LARS). LARS is characterized by the onset of
fecal incontinence, due to injury in the autonomic nerve plexuses that innervate the internal
anal sphincter (IAS); who in turn is responsible for the 52-85% anal resting tone. According
to a recent study, 38.8% and 33.7% of patients with normal preoperative urogenital function,
developed postoperative stool and urine incontinence, respectively.
It becomes apparent that the incidence rates of these complications vary between the various
series, mainly due to their small sample size, the lack of comparative data, the short follow
up period, the use of non-validated tools and their retrospective design. Several predictive
factors of these adverse events have been suggested in the literature, including old age,
tumors located less than 12 cm from the anal verge, preoperative radiotherapy and injury to
the pelvic autonomous nerves.
The clinical and functional anatomy of the pelvis are quite complex. The inferior hypogastric
plexus is formed by the parasympathetic pelvic nerves, deriving from the I2-I4 and the
sympathetic hypogastric nerve. It is a neural anatomic structure that carries organ-specific
nerve fibers. Visual identification of the plexus is quite difficult, for various reasons,
including the complexity of the nerve distribution, the narrow pelvis, the voluminous
mesorectum, obesity, previous pelvic operations, neoadjuvant radiotherapy, locally advanced
tumors, intraoperative bleeding and the extensive use of diathermy. According to the current
literature, identification of the autonomous pelvic plexus is achievable in 72% of cases,
whereas partial localization is possible only in 10.7% of patients.
Theoretically, intraoperative neuromonitoring of the pelvic autonomous nerves (pIONM), could
quantify intraoperative nerve injuries, while in parallel, contribute to the improvement of
the patients' postoperative quality of life. Several pIONM techniques have been described,
including intra-urethral and intra-vesical pressure measurements. However, it was found that
intermittent neuromonitoring objectifies the macroscopic integrity assessment of the sacral
plexus. Recently, a promising technique, based on the simultaneous electromyography of the
IAS and bladder manometry was developed, with encouraging results. During pIONM, the surgeon
delivers electric stimuli to the autonomic nerve structures through a hand-held stimulator.
At the same time, electromyogram changes of the IAS and the external anal sphincter (EAS),
alongside intravesical pressure gradients are assessed.
Intraoperative neuromonitoring has been evaluated in several experimental studies. In a
recent study, intraoperative simulation of the inferior hypogastric plexus with a bipolar
stimulator resulted to the appearance of a measurable and repeatable electromyographic signal
from the IAS.
Simultaneous signal processing from the IAS and urinary bladder, improves the, overall,
diagnostic accuracy of these techniques. Stabilization of the electrodes outside the surgical
field, has been, also, suggested by some researchers. Additionally, experimental studies
evaluated the role of pIONM in the minimal invasive TME.
Moreover, the effectiveness of this technique has been a research subject in multiple
clinical trials. In another study, where 85 patients underwent TME, after logistic
regression, no use of pIONM and neoadjuvant radiotherapy, were identified as independent
prognostic factors of postoperative urogenital deficit. Furthermore, the use of pIONM, was
associated with a 100% sensitivity and a 96% specificity for the postoperative development of
urogenital and anorectal functional complications.
The application of pIONM has been also suggested in the laparoscopic and robotic TME, using
specially designed stimulators. In another trial, preservation of the plexus was achieved in
51.7% of patients submitted to a laparoscopic low anterior resection for rectal cancer.
During one year follow-up, patients receiving pIONM, displayed a superiority in terms of
postoperative urogenital function, as assessed by the IIEF, IPSS and FSFI questionnaires.