Cerebral Functions Monitoring During Awake Craniotomy

Abstract

SUMMARY N owadays there is increased need to cerebral function monitoring during awake craniotomy, an important surgery used for excision of brain tumor from eloquent cortex, epilepsy surgery, and deep brain stimulation surgery. The benefits from this recent technique in monitoring represented in giving the neurosurgeon the ability to increase lesion removal, with growing evidence of improved survival benefit, whilst minimizing damage to eloquent cortex and postoperative neurological dysfunction which always result from this type of surgery. This technique also may enable the surgeon to resect lesion that was considered to be inoperable based on classical anatomical landmark which become inaccurate due to variability in the anatomic location of brain function areas and the displacement caused by the lesion mass itself. Although the previous advantages, the fully awake and cooperative patient during such procedure liable for multiple risks and complications because low level of sedation will expose the patient to stress and hemodynamic instability,also high level of sedation may lead to hypoventilation which represents a problem to anesthetist to control the patient air way in this surgical position. Other complications include nausea and vomiting due to dura traction and convulsion due to brain tissue manipulation itself. From anesthesiological point of view to get success in this operation, patient selection is the most important step and beside basic anesthesiological tests there is pre-operative neurological tests must be done to be used as a base line for brain activity. This test may include electroencephalograghy, Functional magnetic resonance imaging (fMRI), Cognitive function test, diffusion tensor imaging (DTI) and tractography. Intraoperative brain mapping technique which occurs through electroencephalograghy, electromyography, and evoked potentials which are subdivided into: Brainstem auditory evoked potentials (BAEP), visual evoked potentials (VEPs), Somatosensory Evoked Potentials (SSEPs) and motor evoked potentials (MEPs) can be assessed during surgical monitoring under general anesthesia. Although multiple functions of the brain could be monitored when the patient is under general anesthesia via EEG and motor evoked potentials, but functional mapping under awake craniotomy offers the opportunity to accurately localize the motor area and cortex areas responsible for language which couldn’t be assessed under general anesthesia.