Arachnoid cyst status post cyst fenestration in June 2015. There has been interval clearance of the blood products within the fenestrated arachnoid cyst located in the midline of the superior posterior fossa. In addition, the cyst has deceased in size, now measuring up to approximately 10 mm, previously approximately 20 mm, and there is no residual mass effect upon the tectum. There is no evidence of acute infarct. The brain parenchyma and pituitary gland appear unremarkable. The ventricles are unchanged in size and configuration. There is no midline shift or herniation. The major cerebral flow voids are intact. The orbits are grossly unremarkable. There are bilateral maxillary sinus retention cysts.
Interval evolution of postoperative findings related to posterior fossa arachnoid cyst fenestration with interval clearance of associated hemorrhage and decrease in size of the cyst.