Possible arachnoid cyst and abnormal vessel: right side headache, abnormal CT. MRI: There is no evidence of intracranial hemorrhage, mass, or acute infarct. The brain parenchyma and brainstem appear unremarkable. There is focal prominence of cerebrospinal fluid spaces along the inferior aspect of the left cerebellar hemisphere, measuring 10 mm in width, 2 mm in height, and 10 mm anteroposteriorly. The ventricles and basal cisterns are normal in size and configuration. There is no midline shift or herniation. The orbits, skull, paranasal sinuses, and scalp soft tissues are grossly unremarkable.MRA: The vertebrobasilar system is tortuous, but there is no evidence of significant steno-occlusive lesions or cerebral aneurysms.
1. No evidence of arachnoid cyst in the premedullary space. However, a small areas of focal prominence of the cerebrospinal fluid spaces along the inferior aspect of the left cerebellar hemisphere may be attributable to an arachnoid cyst.2. No evidence of cerebral aneurysms.