Arachnoid cyst

Case contributed by Bijaya Shrestha
Diagnosis almost certain


Headache for 4 months, occasional dizziness

Patient Data

Age: 30 years
Gender: Male



Well-circumscribed with an imperceptible wall cystic lesion measuring ~6 x 5.8 cm is seen in the retro cerebellar region in extra-axial space causing scalloping of the adjacent occipital bone following CSF signal intensity in all sequences. Similarly, another extra-axial cystic lesion measuring ~ 3.2 x 2.7 cm seen in the right frontal region with scalloping of the adjacent frontal bone.

Non-specific T2 hyperintensities noted in the cortical and subcortical white matter of bilateral frontal lobes.

Case Discussion

Arachnoid cysts are common cysts of the brain. It is often congenital although head injury or trauma can result in the secondary or acquired arachnoid cyst. The common locations for arachnoid cyst include the middle fossa, posterior fossa, and the suprasellar region. Most cases of arachnoid cysts are asymptomatic. CT scans and MRI are the investigation of choice for an arachnoid cyst.

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