Functional brain mapping and electrophysiological monitoring during awake craniotomy for intraaxial brain lesions

Surgery for intracranial brain lesions located in the dominant hemisphere is associated with a high risk of postoperative speech disturbances. Detection of the functionally important cortical areas can be considered as a critical factor for avoidance of postoperative morbidity and for providing the optimal rate of resection for pathologies with narrow (gliomas) or absent (epileptic focus) microscopic borders with the normal cerebral tissue. Testing of the language function can be done preoperatively with the Wada test, functional MRI, and brain mapping with electrical stimulation after implantation of stereotactic electrodes or grid, and intraoperatively with cortical mapping and electrophysiological monitoring. Awake craniotomy provides the possibility for accurate localization of the eloquent brain areas. It permits us to define clearly the language area, the positive motor area, and the negative motor area, as well as the position of the white matter fibers connected with the speech and motor functions, and prevents both unexpected neurological complications and suboptimal lesion resection. Nevertheless, precise technique and clear differentiation between different types of possible neurophysiological responses are mandatory. Our technique for functional cortical mapping and electrophysiological monitoring during awake craniotomy for intraaxial brain lesions is presented herein.