Cerebellar stroke in elderly patient with basilar artery agenesia: a case report.

We report a case of a 76-year-old woman admitted to our institution with sudden onset of dizziness and vertigo followed by vomiting and blurred vision. Her medical history was remarkable for hypertension, diabetes, and ischemic stroke in the territory of the left cerebral median artery. Her symptoms were suggestive of a cerebellar stroke. Computed tomography brain scan and neck vessel ultrasounds produced normal findings. A 24-hour blood pressure monitoring showed a reverse dipping pattern. Magnetic resonance imaging examination was performed, showing a hyperintense ischemic focus involving pons and left middle cerebellar peduncle, on T2-weighted images. On Time-of-flight (TOF)-3-dimensional magnetic resonance angiography, there was a marked reduction of basilar artery signal. The digital subtraction angiography showed a vertebrobasilar system anomaly. The right vertebral artery was hypoplastic with few thin terminal spinal branches. The left vertebral artery was vicarious to the right one in intracranial tract. V3 to V4 tract showed multiple atherosclerotic wall irregularities. The basilar common trunk was absent. An abnormal posterior inferior cerebellar artery replaced the anterior inferior cerebellar artery and superior cerebellar artery. Right posterior inferior cerebellar artery, anterior inferior cerebellar artery, and superior cerebellar artery arose from ipsilateral V4 tract. This case is the first description of pure basilar agenesia. The symptoms might be related to temporary decrement of the flow in the left vertebral artery. Furthermore, the reverse dipping pattern together with the aging, hypertension, and diabetes had probably contributed to a hemodynamic malfunction of the cerebral vascular system.