Altered mental status [780.97], Reason for Study: ^Reason: eval posterior fossa arachnoid cyst for e/o infection or mass effect in light of AMS History: AMS, hx of aspergillosis and sarcoid There is no evidence of acute ischemic or hemorrhagic lesion.There is no evidence of abnormal enhancement.Scattered high signal intensity lesions on bilateral centrum semiovale on FLAIR imaging are nonspecific findings.There is localized lacunar infarct on the right supra marginal gyrus.Posterior fossa arachnoid cyst is again seen. The configuration of the boundary between the right side posterior fossa arachnoid cyst and right cerebellar hemisphere appear to be straight line instead of following the margin of right cerebellar hemisphere which may suggest possibility of mass effect of the arachnoid cyst against the right cerebellar hemisphere. However, the MR I clearly shows the normal definition of right the cerebellar sulci and folia without evidence of edema. Therefore, there is no definitive MR imaging evidence of mass effect of arachnoid cyst toward the right cerebellar hemisphere.The ventricles, sulci are symmetric and unremarkable. There is no mass, edema, midline shift, intra or extra-axial fluid collection/hemorrhage, restricted diffusion/acute ischemia, or abnormal contrast enhancement. The midline structures and cranial-cervical junction are normal. Normal flow voids are identified in the major intracranial vessels. The paranasal sinuses and mastoid air cells are clear.
1. No evidence of acute ischemic or hemorrhagic lesion. No abnormal contrast enhancement. No evidence of infected arachnoid cyst.2. Posterior fossa arachnoid cyst is again seen without definitive MR imaging evidence of mass effect towards especially right cerebellar hemisphere.