Bilateral thalamic lesions mimicking a tumor: Do not miss a dural arteriovenous fistula

Background: Bilateral thalamic lesions on MRI often suggest neoplastic or inflammatory processes. However, dural arteriovenous fistulas (dAVFs) with deep venous drainage may mimic such appearances and lead to diagnostic delays or iatrogenic complications. Case summary: A 46-year-old man presented with persistent left facial and hand paresthesia after minor elbow trauma. Initial MRI demonstrated right thalamic hyperintensities, bilateral patchy enhancement, and susceptibility artifacts, raising suspicion of a tumor. Stereotactic biopsy was scheduled. Upon preoperative re-evaluation, a prominently dilated vein of Galen prompted digital subtraction angiography (DSA), revealing a Borden type III/Lawton type 1 dAVF. The fistula was successfully treated endovascularly, leading to complete neurological recovery. Conclusions: This case highlights the importance of considering vascular etiologies in bilateral thalamic lesions. Prompt vascular imaging may prevent misdiagnosis, avoid unnecessary interventions, and facilitate curative therapy.