[Ruptured aneurysm at the anomalous arterial wall of the distal anterior inferior cerebellar artery: a case report].

Distal anterior inferior cerebellar artery(AICA)aneurysms are rare, so its pathogenesis and treatment remain controversial. Here, we report the unique pathogenesis of a ruptured aneurysm in this area that was based on anomalous components as well as partial dissection of the arterial wall. A 61-year-old woman presented to our hospital with sudden headache and nausea. On admission, neurological examination revealed slight consciousness disturbance. Computed tomography(CT)of the head showed a clotted subarachnoid hemorrhage(SAH)that was dominant in the right cerebellopontine and prepontine cistern. Three-dimensional CT angiography detected an irregular fusiform aneurysm 4.5×3.2mm in size in the distal portion of the AICA. The patient underwent trapping without distal vascular reconstruction by the lateral suboccipital approach. After surgery, she experienced right hearing disturbance and ipsilateral facial palsy that were considered to be caused by vasogenic edema at the cerebellar peduncle that resulted from the initial SAH damage. Pathology revealed an aneurysmal wall with anomalous components and arterial dissection in the arterial wall. To our knowledge, only one article has reported the histological findings of a distal AICA aneurysm. Based on the pathology of this case, these findings may suggest a useful treatment strategy for this rare aneurysm.