Non-aneurysmal Subarachnoid Hemorrhage Due to an Aplastic or Twig-Like Middle Cerebral Artery Diagnosed by Cone Beam CT and M1 Selective Angiography: A Case Report.

A non-aneurysmal subarachnoid hemorrhage (SAH) due to an aplastic or twig-like middle cerebral artery (Ap/T-MCA) is extremely rare. We describe a case of a non-aneurysmal SAH due to an Ap/T-MCA. A 38-year-old female patient experienced a sudden severe headache and was admitted to our hospital. A head CT scan revealed an SAH. Cerebral angiography revealed a non-aneurysmal subarachnoid hemorrhage due to an Ap/T-MCA. The patient was treated conservatively and had a good recovery. Because of the complexity of the vascular structure, we had difficulty in making a diagnosis of our case. Cone beam CT and M1 selective angiography using a microcatheter were useful for the diagnosis of an Ap/T-MCA. An extracranial-intracranial bypass (EC-IC) may effectively treat a non-aneurysmal SAH due to an Ap/T-MCA. However, the evidence of the effectiveness of EC-IC bypass surgeries for non-aneurysmal SAHs due to Ap/T-MCAs is insufficient, and further case accumulation is needed.