High-grade dural arteriovenous fistula simulating a bilateral thalamic neoplasm.

Dural arteriovenous fistulae (dAVF) provide a diagnostic challenge and must be part of a broad differential in pursuit of a difficult diagnosis or unusual presentation. This case report demonstrates an initially misguided diagnosis of bilateral thalamic neoplasm and demonstrates the importance of continued pursuit until the correct diagnosis is obtained. Moreover, to our knowledge, this is the first reported case of a dAVF simulating a bilateral thalamic neoplasm. We present a patient with a provisional diagnosis of bilateral thalamic neoplasm based on clinical history and an advanced imaging workup including MR spectroscopy. Subsequent biopsy suggested venous congestion, hypoxia, and edema without neoplasia. Routine post-operative CT the following day revealed suggestion of dAVF due to the presence of residual contrast from prior unrelated abdominal CT. Cerebral angiography eventually revealed a Cognard grade IIb dAVF. Trans-arterial Onyx embolization resulted in a dramatic clinical and radiographic improvement. This case highlights an unusual presentation and challenging diagnosis of a dAVF and the importance of pursuing the correct diagnosis.