Spontaneous middle meningeal arteriovenous fistula without cortical venous reflux presenting with acute subdural hematoma: illustrative case.

BACKGROUND: Dural arteriovenous fistula (AVF) without cortical venous reflux (CVR) has a relatively benign course. Here, the authors describe a patient presenting with subdural hematoma due to a middle meningeal AVF without CVR. OBSERVATIONS: A 17-year-old male was admitted to the emergency department with acute headache without an episode of head trauma. Computed tomography demonstrated a left acute subdural hematoma (SDH). Because the nontraumatic SDH raised the suspicion of vascular pathology, emergent angiography was performed, which demonstrated an AVF fed by the middle meningeal artery and draining to the diploic vein via the serpentine meningeal vein without CVR. T2-weighted magnetic resonance imaging (MRI) revealed no signs of venous congestion. Given the proximity of the AVF to the SDH and the MRI findings, we suspected that the serpentine meningeal vein was responsible for the SDH. The patient was successfully treated with transarterial Onyx embolization. During the injection, Onyx migrated to the extravascular space following its penetration into the serpentine meningeal vein, suggesting the meningeal vein was a bleeding source of the subdural hematoma. LESSONS: Despite the absence of cortical venous reflux, serpentine meningeal venous drainage of middle meningeal AVF can be a source of subdural hemorrhage.