Two cases of a dural arteriovenous fistula mimicking a brain tumor

Dural arteriovenous fistula (d-AVF) is relatively rare. Some cases of atypical locations are often difficult to distinguish from other vascular disorders or tumors because those d-AVFs show various onsets, such as subcortical bleeding and venous infarctions. We encountered two cases of d-AVF with severe brain edema that took adequate time to distinguish from brain tumors. A 68-year-old man visited his local physician complaining of dizziness. He was diagnosed with a cerebral infarction due to the presence of an abnormal cerebellar signal on magnetic resonance imaging (MRI) and was treated by drip infusion. However, he did not recover and was admitted to our hospital with suspicion of a brain tumor. A 75-year-old woman with an onset of progressive dementia and gait disturbance showed severe edema of the right-front temporal lobe on MRI. Both these cases were examined by single photon emission computed tomography or positron emission tomography and were scheduled for craniotomy and biopsy based on the diagnosis of brain tumor. We performed preoperative angiography and found d-AVFs. We embolized the d-AVFs with liquid material and both patients recovered well. Brain edema from d-AVF or a tumor can be distinguished by carefully reading the MRI with findings such as the distribution of the edemas, differences on diffusion-weighted images, and contrast-enhanced images. Therefore, it is important to provide initial accurate diagnoses to prevent patient mistrust and irreversible disease conditions.