T1 post-gad T2

Diagnosis: Arachnoid cyst

Arachnoid cysts are probably congenital meningeal malformations and make up 1% of nontraumatic intracranial masses. Most occur in childhood with boys outnumbering girls 3 to 1. Over 1/2 are in the middle cranial fossa. 75% may be symptomatic, presenting with seizures, headache or focal neurologic deficit. They contain fluid which is similar , but not identical to CSF. Hemorrhage into the cyst is a possible complication. The cyst itself should have no internal components. There may be pressure erosion of the adjacent calvarium and temporal lobe hypoplasia. Post-op changes or infarct with resulting porencephalic cyst might resemble this. However, the expansion of the inferior temporal gyrus would be atypical. In the posterior fossa, epidermoid is the major differential possibility. Related Cases

Pineal Epidermoid Arachnoid cyst Velum interpositum cyst