Middle cranial fossa arachnoid cyst (Galassi type II)
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A large, well defined, CSF signal intensity lesion in the right middle cranial fossa displacing the temporal lobe posteriorly. There is no restricted diffusion, no solid component, no enhancement, no hemorrhage or calcification.
No adjacent infiltrative or inflammatory changes.
Features are characteristic of an arachnoid cyst. (Galassi type II)
Intracranial arachnoid cysts more frequently occur in the middle cranial fossa. They have characteristic Features on MR imaging. Their differentiation with epidermoid cysts can mainly be done on diffusion weighted images. Galassi classification is still widely used classification for middle cranial fossa arachnoid cysts.