Lessons learned from awake brain function mapping in aggressive multimodal resection of oligodendrogliomas

Oligodendrogliomas are diffusely infiltrating tumors that grow through white matter pathways. While these tumors are deadly in the long term and should be treated operatively whenever possible, their predisposition for eloquent tracts requires a compromise between preserving function and resecting tumor. Modern techniques of investigating functional neuroanatomy have demonstrated the variability of eloquent tracts, highlighting the misleading nature of Broca’s and Wernicke’s areas as fixed notions in modern neurosurgery. Given that traditional landmarks of functional neuroanatomy are too inconsistent to be used reliably in tumor patients, speech mapping is used intraoperatively to identify sites critical to language in order to preserve language function. The awake patient performs naming and other language functions with the help of a speech pathology team, while the surgeon conducts cortical and subcortical electric stimulation to map out and avoid eloquent brain areas. With this multidisciplinary care, the vast majority of patients are not harmed by surgery. Here we review speech mapping in oligodendroglioma operations and provide data regarding patient outcomes with these methods.