一過性脳虚血発作を呈した2年後に頭蓋内出血を生じたaplastic or twig-like middle cerebral arteryの1例

A Case of Aplastic or Twig-Like Middle Cerebral Artery Presenting with an Intracranial Hemorrhage Two Years after a Transient Ischemic Attack

Ⅰ．はじめに

　Aplastic or twig-like middle cerebral artery（Ap/T-MCA）は稀な中大脳動脈（MCA）のanomalyであるが，これまでに頭蓋内出血や脳梗塞に関連するとの報告が散見される^2,3,5)．今回われわれは一過性脳虚血発作を呈した2年後に，頭蓋内出血を発症したAp/T-MCAの1例を経験したため，文献的考察を加え報告する．

　Aplastic or twig-like middle cerebral artery（Ap/T-MCA）is a rare anatomical anomaly, which can be associated with intracranial hemorrhage and cerebral ischemia.

　A 52-year-old woman who presented with sudden headache was admitted to our hospital. Computed tomography（CT）and magnetic resonance imaging showed no abnormality；however, magnetic resonance angiogram revealed an occlusion or severe stenosis in the left middle cerebral artery. Three-dimensional CT angiography demonstrated severe stenosis in the left middle cerebral artery. The patient was discharged without any neurological deficit；however, she subsequently complained of temporary weakness in the right hand. It was possibly due to a transient ischemic attack；therefore, cilostazol 200 mg/day was administered for prevention of cerebral ischemia. Single photon emission computed tomography（with or without administration of acetazolamide）showed neither significant decrease in the cerebral blood flow nor cerebrovascular reactivity；hence, surgical revascularization was not performed. However, two years after the initial admission, she was urgently admitted to our hospital with sudden headache and nausea followed by aphasia and weakness of the right extremities. CT images showed diffuse subarachnoid hemorrhage and intracerebral hemorrhage in the left temporo-parietal lobe. Cerebral angiography revealed that the left middle cerebral artery was Ap/T-MCA without cerebral aneurysms. The patient was treated conservatively, and she eventually recovered without any neurological deficit except mild aphasia.

　Since Ap/T-MCA is associated with both hemorrhagic and ischemic stroke, antiplatelet therapy should be administered carefully. Moreover, it is necessary to consider extracranial-intracranial bypass to reduce hemodynamic stress on the abnormal vessels.