Presentation
Right-sided hearing loss.
Patient Data
Large right middle cranial fossa cystic lesion with long-standing mass effect evidenced by calvarial expansion and thinning. Contents are slightly higher than CSF on T1WI with incomplete FLAIR suppression. Inhomogeneous FLAIR signal is thought to represent flow artifact. No abnormal diffusion restriction. Leftward midline shift and right uncal prominence at the tentorium cerebelli.
The patient was referred to neurosurgeons for review with a consensus diagnosis of a Galassi type 3 arachnoid cyst. The cause of the hearing loss was not determined. Routine follow-up was performed 18 months later.
Right middle cranial fossa extra-axial cyst that is smaller than the previous with internal signal intermediate-high T1 signal and very high T2 signal without FLAIR suppression. Dependent lobular low T1 and T2 signal with blooming and a low T2 signal rim. Superficial siderosis along the right cerebral convexity. No abnormally restricted diffusion.
No hydrocephalus. No midline shift although there is right uncal prominence at the tentorium cerebelli.
Bony remodeling and expansion of the right calvarium and middle cranial fossa..
Case Discussion
Large right middle cranial fossa arachnoid cyst with signal characteristics of intracystic hemorrhage as well as superficial siderosis. On the first study, the cyst signal does not completely follow CSF suggesting proteinaceous material, presumably from hemorrhage whereas on the follow-up study, it is clear there has been further hemorrhage within and around the cyst.
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