Evaluate arachnoid cyst. History of acute lymphoid leukemia. There is an arachnoid cyst in the anterior right middle cranial fossa extending into the anterior cranial fossa which measures 7.8 cm x 6.0 cm axially and 7.0 cm craniocaudally. It is located just lateral to the branches of the right middle cerebral artery. It causes mild mass-effect on the adjacent brain parenchyma and splays the frontal and temporal gyri along the anterior part of the sylvian fissure. It also causes mild uncal herniation. However there is no brain parenchymal signal abnormality. It causes up to 6 mm of midline shift at the level of the septum pellucidum. There is no acute infarct or intracranial hemorrhage. Few dilated prevascular spaces are present within the right frontal white-matter. Major intracranial flow voids are preserved. Following contrast administration, there is no abnormal intracranial contrast enhancement.The arachnoid cyst thins the calvarium and expands the right middle cranial fossa. The remainder of the skull is unremarkable. There is no gross orbital abnormality. There is trace mucosal thickening in the paranasal sinuses.The CSF study performed at the mid sagittal plane shows preserved, ventral and dorsal biphasic CSF flow.
Right frontotemporal arachnoid cyst with mass-effect as described above. Brain MRI is otherwise unremarkable.