Bilateral internal carotid artery hypoplasia and multiple posterior circulation aneurysms. Importance of 3DCTA for the diagnosis.

We present a case with bilateral internal carotid artery hypoplasia and multiple posterior circulation aneurysms who was diagnosed following a subarachnoid hemorrhage. The patient was admitted to our clinic with a history of sudden and severe headache with short-term loss of consciousness and being unable to open the right eyelid five days ago. Nuchal rigidity and right partial ophthalmoplegia were found during the examination. Computed tomography revealed a subarachnoid hemorrhage. Digital subtraction angiography showed bilateral internal carotid artery hypoplasia while three-dimensional computed tomographic angiography showed bilateral internal carotid artery hypoplasia and multiple posterior circulation aneurysms. The aneurysms arising from the right posterior cerebral artery (P1 segment) and left superior cerebellar artery region were clipped using the right modified pterional approach. Asymptomatic unilateral or bilateral internal carotid artery hypoplasia may not be an important problem. However, other concurrent anomalies may be potentially life-threatening. These aneurysms must be treated due to the marked hemodynamic stress even if they have not ruptured and are asymptomatic. It may not be possible to see the aneurysm with digital subtraction angiography in these cases due to superimposition. Three-dimensional computed tomographic angiography provides more detailed diagnostic information.