Recurrent nontraumatic acute subdural hematoma secondary to ruptured accessory meningeal artery aneurysm: A case report and literature review.

Spontaneous acute subdural hematoma (aSDH) is an uncommon neurosurgical emergency, and aneurysms of the accessory meningeal artery (AMA) are an exceptionally rare cause. We report a case of recurrent spontaneous aSDH attributed to rupture of an AMA aneurysm, which was identified as the most likely source of both the initial and recurrent hemorrhages, successfully treated with endovascular embolization. A 36-year-old hypertensive man presented with progressive headache and drowsiness without preceding trauma. Computed tomography (CT) demonstrated a left convexity acute-on-chronic subdural hematoma with significant mass effect, while CT angiography revealed no vascular abnormality. Emergency decompressive craniectomy and hematoma evacuation were performed, but no bleeding source was identified. Although the patient initially recovered well, he developed recurrent aSDH one week later. Digital subtraction angiography (DSA) subsequently identified a saccular aneurysm arising from the accessory meningeal artery. Endovascular coil embolization achieved complete aneurysm occlusion with no further recurrence, and the patient remained neurologically intact. This case highlights that ruptured AMA aneurysms may remain occult despite negative CT angiography and should be considered in unexplained or recurrent nontraumatic aSDH. Early DSA is essential for definitive diagnosis, and prompt endovascular treatment can prevent recurrence and achieve favorable neurological outcomes.