OBJECTIVE: The treatment of brain arteriovenous malformations (BAVMs) supplied by the anterior choroidal artery (AChA), or aBAVMs, remains challenging. The aim of this study was to determine the surgical outcomes and risk factors for worsened muscle strength (MS) after surgery in patients with aBAVMs. METHODS: We retrospectively reviewed 266 consecutive patients with BAVMs who underwent microsurgical resection of their BAVMs between September 2012 and June 2016. Patients were included if the BAVMs were entirely or partially supplied by the AChA. All patients had undergone preoperative diffusion tensor imaging, magnetic resonance imaging, 3-dimensional time-of-flight magnetic resonance angiography, and digital subtraction angiography followed by resection. Both functional and angioarchitectural factors were analyzed with respect to the change in MS. RESULTS: We identified 29 patients with aBAVMs who underwent surgical resection of the nidus. Radical resection was achieved in all patients. Thirteen (44.8%) patients suffered from postoperative short-term and 11 (37.9%) suffered from long-term MS deterioration. A shorter lesion-tocorticospinal tract distance (LCD) (P = 0.004) was significantly associated with postoperative short-term worsened MS. Shorter LCD (P = 0.018) and nidus supplied by cisternal segment of AChA (P = 0.026) were independent risk factors for the long-term MS worsening. The amplitudes and potential changes of intraoperative motor-evoked potential monitoring were consistent with the surgical outcomes. CONCLUSIONS: Surgical treatment of aBAVMs can cause a high incidence of MS deficits. Niduses supplied by cisternal segment of AChA and shorter LCD were crucial risk factors for postoperative MS worsening. Motor-evoked potential monitoring was an effective intraoperative technique to predict postoperative MS deficits.