The study will prospectively enroll subjects who have primary or secondary brain tumors located near the motor pathway (corticospinal tract) or language pathway (arcuate fasciculus). This is a nonrandomized study in which each subject will receive the standard of care as per the treating neurosurgeon.

W/I approx 4-6 weeks of the fMRI, DTI & DSI, neurological/physical testing & brain MRI showing tumor &/or edema located in or near (<2 cm) the motor cortex (precentral gyrus), motor pathway (corticospinal tract), language cortex (Broca's area, Wernicke's area), &/or language pathway (arcuate fasciculus) Preoperative MRI for surgical planning (approximately <48 hours before surgery*) fMRI to localize gray matter DTI, DSI & tractography to localize white matter, DSI & updated fMRI (Optional) Most patients will undergo surgery w/i 48 hrs of their preoperative MRI. For some patients, the MRI results will be used for preoperative counseling. In this subset of patients, we expect that surgery will occur w/i 3-4 months of the MRI. Brain tumor resection as per the treating neurosurgeon Electrical stimulation to localize gray &/or white matter structures if clinically necessary according to the standard of care at MSKCC Postoperative neurological/physical examination (<48 hours after surgery)

The standard and probabilistic tractography results will be compared to expected anatomy as determined by expert operators. The reconstructed tracts will be examined for their configurations near the tumor and/or edema, and the completeness of their courses. All analyses will be scored by two expert operators (2 board certified radiologists who hold Certificates of Added Qualification in Neuroradiology and are familiar with DTI and tractography), with disagreements resolved by consensus.

(Optional) DSI is a newly proposed modification of DTI that allows potentially improved visualization of the complex white matter architecture. Recent technical advances have allowed marked reduction of the DSI scan time to match other clinical scan times. DSI in brain tumor patients has not been described Analysis of the DSI results will be performed in a manner similar to the analysis for DTI in Specific Aim #1. Briefly, the endings of the rostral language tracts will be graded as: 0-none; 1-few; 2-some; or 3-all for tracts extending to the fMRI activated Broca's area. Both motor and language tracts will be compared to the contralateral mirror tract using a similar 0-3 scale (0-absent, 3-normal) by two expert operators with disagreements resolved by consensus.