Functional magnetic resonance imaging-guided resection of low-grade gliomas

Background: We sought to determine the safety and efficacy of using functional magnetic resonance imaging (fMRI) to guide the resection of low-grade gliomas (LGG). Methods: From September 1997 to February 2003, fMRI was performed in 16 patients (age, 15-43 years) before an attempted surgical resection of LGG. Functional imaging was used to identify and coregister eloquent cortices pertinent to motor (10), speech (3), motor and speech (2), and short-term memory and speech (1) activation with respect to the tumor using a 1.5-T interventional MRI system. Intraoperatively acquired T₂- weighted and turbo-fluid attenuated inversion recovery images were used to assess the completeness of surgical resection. Results: Tumors included 10 oligodendrogliomas, 4 astrocytomas, 1 dysembryoplastic neuroepithelial tumor, and 1 pleomorphic xanthoastrocytoma. In every case, the preoperative brain activation study accurately determined the location of neurologic function. After surgery, one patient had a transient hemiparesis and another had a temporary apraxia. Ten patients had radiographically complete resections and 5 with oligodendrogliomas had incomplete resections because of the proximity of their tumors to functional areas. Only one patient with an astrocytoma in the motor strip received postoperative radiation therapy. To date, radiographic tumor progression has not been seen in any patient with either a partial or a complete resection with a median follow-up of 25 months (range, 12-87 months). Conclusions: Functional MRI was accurate for identifying areas of neurologic function before surgical resection of LGG. Patients with complete radiographic resections or with incompletely resected oligodendrogliomas can be safely followed radiographically after surgery. Radiation therapy was reserved for infiltrating astrocytomas that were not completely resectable.