Basilar Apex Aneurysm Manifesting as Third Ventricular Mass and Obstructive Hydrocephalus

A 58-year-old male, with a past history of hypertensive thalamic hemorrhage 12 years before, presented with gradually exaggerating gait disturbance, memory disturbance, and urinary incontinence. On admission, he had gait disturbance represented by petit pas and anteropulsion in addition to significant recent memory disturbance. Cranial computed tomography (CT) revealed a hyperdense mass in the third ventricle with triventricular dilation. Cerebral magnetic resonance (MR) imaging and MR angiography identified the third ventricular lesion as saccular basilar apex aneurysm. No other intracranial abnormal intensity contributing to his clinical symptoms was recognized. Cervical MR angiography showed normal findings. Cerebral blood flow (CBF) measurements revealed diffuse CBF reduction in the cerebral hemisphere. The patient underwent coil embolization which accomplished complete aneurysm occlusion. He showed only slight improvement in his gait disturbance after embolization, and CT following embolization revealed persistent ventriculomegaly. Ventriculoperitoneal shunting was carried out. Intraoperative neuroendoscopy demonstrated cerebrospinal fluid (CSF) obstruction caused by the embolized aneurysm at the level of the third ventricle, with normal CSF findings. Postoperatively his gait disturbance and intellectual impairment showed remarkable improvement. Basilar apex aneurysm associated with obstructive hydrocephalus has complex underlying pathology and should be treated by a combination of definitive aneurysm obliteration and CSF diversion.