Brain cyst, follow-up evaluation. There is no diffusion weighted or susceptibility weighted abnormality. The ventricles and sulci are within normal limits. The basal cisterns remain patent. There is no midline shift. There is prominence of the extra-axial space along the posterior aspect of the left posterior fossa which is of CSF signal intensity without diffusion restriction. This measures approximately 6.2 cm x 2.5 cm in AP and transverse dimensions and unchanged. There is mild associated mass effect on the left cerebellar hemisphere and mild scalloping of the occipital calvarium. There is also unchanged slight prominence of the supracerebellar cistern. Normal flow-voids are demonstrated in the major intracranial vascular structures. The midline structures and craniocervical junction are within normal limits.
Unchanged cystic lesion in the posterior fossa on the left likely representing an arachnoid cyst. MRI of the brain is otherwise unremarkable.