The authors report a case in which the clinical and neuroimaging findings were initially considered diagnostic of a brainstem glioma. Angiography revealed a deep venous system (galenic) dural arteriovenous fistula causing brainstem interstitial edema. Successful endovascular surgery resulted in complete clinical recovery of the patient and resolution of the structural abnormalities that had been observed on magnetic resonance images. The neuroimaging and therapeutic significance of this case are discussed.