Experimental study for identification of the facial colliculus using electromyography and antidromic evoked potentials

Focal brainstem gliomas. Advances in intra-operative management

Improved neuronavigation guidance as well as intraoperative imaging and neurophysiologic monitoring technologies have enhanced the ability of neurosurgeons to resect focal brainstem gliomas. In contrast, diffuse brainstem gliomas are considered to be inoperable lesions. This article is a continuation of an article that discussed brainstem glioma diagnostics, imaging, and classification. Here, we address open surgical treatment of and approaches to focal, dorsally exophytic, and cervicomedullary brainstem gliomas. Intraoperative neuronavigation, intraoperative neurophysiologic monitoring, as well as intraoperative imaging are discussed as adjunctive measures to help render these procedures safer, more acute, and closer to achieving surgical goals.

The importance of brainstem mapping in brainstem surgical anatomy before the fourth ventricle and implication for intraoperative neurophysiological mapping

Brain stem mapping (BSM) is an intraoperative neurophysiological procedure to localize cranial motor nuclei on the floor of the fourth ventricle. BSM enables neurosurgeon to understand functional anatomy on the distorted floor of the fourth ventricle, thus, it is emerging as an indispensable tool for challenging brain stem surgery. The authors described the detail of BSM with the special emphasis on its clinical application for the brain stem lesion. Surgical implications based on the result of brains stem mapping would be also informative before planning a brain stem surgery through the floor of fourth ventricle. Despite the recent advancement of MRI to depict the lesion in the brain stem, BSM remains as the only way to provide surgical anatomy in the operative field. BSM could guide a neurosurgeon to the inside of brain stem while preventing direct damage to the cranial motor nuclei on the floor of the fourth ventricle. It is expected that understanding its advantage and limitations would help neurosurgeon to perform safer surgery to the brain stem lesion.

Motor evoked potential monitoring for spinal cord and brain stem surgery

Intraoperative Neurophysiology (ION) has established itself as one of the means by which modern neurosurgery can improve surgical results while minimizing morbidity. The advent of motor evoked potential (MEP) monitoring represents a landmark in this recent progress. ION consists of monitoring (the continuous "on-line" assessment of the functional integrity of neural pathways) and mapping (the functional identification and preservation of anatomically ambiguous nervous tissue) techniques. In this chapter we have attempted to critically review the evolution of MEP use during monitoring and mapping techniques for neurosurgical procedures in the brainstem and the spinal cord, providing the neurophysiological theoretical background and practical aspects of clinical applications. According to the experience from our and other groups involved in ION, we suggest the following: 1) ION is mandatory whenever neurological complications are expected as predicted by a known pathophysiological mechanism. It is therefore advisable to perform ION when dealing with brain stem and intramedullary spinal cord lesions. 2) MEP monitoring after transcranial electrical stimulation is today a feasible and reliable technique for use under general anesthesia. MEP monitoring is the most appropriate technique to assess the functional integrity of descending motor pathways in the brainstem and, foremost, in the spinal cord. 3) Mapping of the corticospinal tract at the level of the cerebral peduncle as well as mapping of the VII, IX-X and XII cranial nerve motor nuclei on the floor of the fourth ventricle is of great value with which to identify "safe entry zones" into the brainstem. 4) Other techniques, although safe and feasible, still lack rigorous validation in terms of prognostic value and correlation with the postoperative neurological outcome. These techniques include mapping of the corticospinal tract within the spinal cord and monitoring of the corticobulbar tracts. These techniques, however, are expected to open new perspectives in the near future.