OBJECTIVE: The relationship between preoperative functional findings, derived from functional magnetic resonance imaging and diffusion tensor imaging, and surgical outcomes in patients with motor cortical arteriovenous malformations (AVMs) has not been determined. The aim of this study was to determine the relationship between preoperative functional findings and surgical outcomes in patients with motor cortical AVM. METHODS: Fifteen patients with AVM involving the precentral knob and/or paracentral lobule were reviewed. Each motor function involved was examined as an independent object. Preoperative functional findings included cortical reorganization, activation around the nidus, corticospinal tract (CST) reorganization, nidus involving the CST, and the level of the CST involved. The relationship between preoperative functional findings and surgical outcomes was analyzed statistically. A muscle strength of grade 3 or less was defined as a poor outcome after surgery, and a muscle strength of grade 4 or greater was defined as a good outcome. RESULTS: Eighteen objects were created and analyzed. Cortical reorganization (P = 1.000) was not correlated with surgical outcomes. However, nidus involving the CST was significantly associated with poor short-term outcomes (1 week after surgery) (P = 0.028) and permanent deficit in muscle strength (P = 0.042). Most of the objects had good outcomes (16/18, 88.9%) at 6 months after surgery (long-term outcomes). Only 1 patient with CST ruptured at the corona radiata level and 1 patient who had postoperative hemorrhage obtained poor long-term outcomes. CONCLUSIONS: Nidus involving the CST and the level of the CST involved, rather than cortical reorganization, may be associated with surgical outcomes in patients with motor cortical AVM.