The Role of Functional MRI in Intracranial Glioma Resection

It is generally accepted that tumor extirpation constitutes the treatment goal in cases of intracranial tumors. It is also well known that intracranial gliomas are infiltrative lesions with ill-defined borders, and their total resection is often quite challenging. Moreover, the presence of a glioma in an eloquent cortical area may make its extirpation even more difficult. It has been demonstrated that extensive glioma resection is associated with prolonged survival and better quality of life, and the overall outcome of patients with intracranial gliomas is associated with the extent of the tumor’s surgical resection [Lacroix et al., 2001; McDonald et al., 1999; National Comprehensive Cancer Network, 2007; Sanai & Berger, 2008; Stafford et al., 1998). Therefore, every effort to achieve maximal tumor resection without jeopardizing vital neuronal functions becomes of paramount importance in cases of intracranial gliomas. Exact knowledge of the cortical topography, accurate identification of all eloquent cortical areas as well as delineation of their relationships with the tumor, constitute key elements in avoiding all functional cortical areas, while aggressive tumor resection is accomplished. It is well known that conventional imaging studies providing pure structural anatomical information are not sufficient for identifying and localizing functional cortical areas, since there are frequent anatomical variations, and cortical functional center shift due to brain distortion and plasticity, particularly in glioma cases. Various methodologies have been developed for identifying different functional areas of the cerebral cortex and accurately localize them, in regard to the studied tumor on each individual case. Intraoperative electrophysiological studies such as recording of Somato-Sensory Evoked Potentials (SSEPs), Motor Evoked Potentials (MEPs), Direct Cortical Stimulation (DCS), and spontaneous Electro-Myo-Graphy (sEMG) are considered the gold standard for cortical mapping and delineation of functional cortical networks. The major drawback of these methodologies however, is the fact that all are invasive tests and cannot provide all this valuable information preoperatively. Thus, the development of non-invasive tests for cortical mapping seems to be mandatory. Recently, advanced imaging and electrophysiological studies such as Positron Emission Tomography (PET), brain SPECT imaging, functional