Neurophysiological Monitoring and Awake Craniotomy for Resection of Intracranial Gliomas

Abstract

Aggressive resection of intracranial gliomas has a positive impact on patients' prognosis, but is associated with a risk of neurological complications. For preservation of brain functions and avoidance of major postoperative morbidity various methods of intraoperative neurophysiological monitoring have been introduced into clinical practice. At present, somatosensory evoked potentials (SSEP), motor evoked potentials (MEP), visual evoked potentials (VEP), brainstem auditory evoked potentials (BAEP), and electrocorticography (ECoG) are used routinely during neurosurgical procedures. To maximize the efficacy of these neurophysiological techniques, it is most preferable to apply total intravenous anesthesia with continuous infusion of propofol and opioids and avoidance of long-acting muscle relaxants. Surgery for brainstem gliomas requires specific mapping with direct electrical stimulation (DES), corticobulbar tract MEP monitoring, and free-running electromyography (EMG) of the various muscles innervated by the cranial nerves. Awake craniotomy and intraoperative mapping of language and sensorimotor functions with DES allow precise identification of the functionally important neuronal structures and have become standard techniques for removal of cerebral neoplasms affecting eloquent cortical areas and subcortical pathways. Overall, contemporary neurophysiology plays a very important role in guidance of brain tumor surgery, in which it helps to maximize the extent of resection and to minimize the risk of permanent neurological morbidity.