Intraoperative neurophysiological monitoring in pediatric neurosurgery: why, when, how?

Abstract

In compiling this review, controversies about indications, methodologies and the usefulness of some INM techniques have surfaced. These discrepancies are often due to lack of familiarity with new techniques in groups from around the globe. Accordingly, internationally accepted guidelines for INM are still far from being established. Nevertheless, the studies reviewed provide sufficient evidence to enable us to make the following recommendations. (1) INM is mandatory whenever neurological complications are expected on the basis of a known pathophysiological mechanism. INM becomes optional when its role is limited to predicting postoperative outcome or it is used for purely research purposes. (2) INM should always be performed when any of the following are involved: supratentorial lesions in the central region and language-related cortex; brain stem tumors; intramedullary spinal cord tumors; conus-cauda equina tumors; rhizotomy for relief of spasticity; spina bifida with tethered cord. (3) Monitoring of motor evoked potentials (MEPs) is now a feasible and reliable technique that can be used under general anesthesia. MEP monitoring is the most appropriate technique to assess the functional integrity of descending motor pathways in the brain, the brain stem and, especially, the spinal cord. (4) Somatosensory evoked potential (SEP) monitoring is of value in assessment of the functional integrity of sensory pathways leading from the peripheral nerve, through the dorsal column and to the sensory cortex. SEPs cannot provide reliable information on the functional integrity of the motor system (for which MEPs should be used). (5) Monitoring of brain stem auditory evoked potentials remains a standard technique during surgery in the brain stem, the cerebellopontine angle, and the posterior fossa. (6) Mapping techniques (such as the phase reversal and the direct cortical/subcortical stimulation techniques) are invaluable and strongly recommended for brain surgery in eloquent cortex or along subcortical motor pathways. (7) Mapping of the motor nuclei of the VIIth, IXth-Xth and XIIth cranial nerves on the floor of the fourth ventricle is of great value in identification of "safe entry zones" into the brain stem. Techniques for mapping cranial nerves in the cerebellopontine angle and cauda equina have also been standardized. Other techniques, although safe and feasible, still lack a strong validation in terms of prognostic value and correlation with the postoperative neurological outcome. These techniques include monitoring of the bulbocavernosus reflex, monitoring of the corticobulbar tracts, and mapping of the dorsal columns. These techniques, however, are expected to open up new perspectives in the near future.

Multimodal intraoperative monitoring during surgery of spinal deformities in 217 patients

“…The concept of monitoring guiding surgery in spinal disorders, particularly in intramedullary tumour was introduced by the group of Epstein in the 1980s and 1990s [8,3] which was introduced in our institution in the late 1990s by personal communication from both pioneering groups (Tamaki, Epstein). The close collaboration between neurologist specially trained in the monitoring techniques and the spine surgeon already during the preoperative planning stage facilitated the communication during the surgical procedure.…”

The diagnostic value of multimodal intraoperative monitoring (MIOM) during spine surgery: a prospective study of 1,017 patients

“…The review papers published by well experienced experts [3,4,13,15] conclude that spinal cord monitoring is a team effort involving the surgeon, the neurophysiologist/neurologist and the anaesthetist to improve surgical outcome, primarily for the patient, but also for the surgeon and the spine centre in general.…”

Transcranial Motor-Evoked Potentials

“…Total or subtotal tumor resection was done in only 11% of patients prior to motor mapping but 69.8% after motor mapping was initiated [ 55 ] . A number of other groups have published similar reports and noted that the long-term outcome is significantly improved by more extensive tumor resection in both children and adults for all supratentorial tumors [ 56,57 ] .…”