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Arachnoid cyst

Case contributed by Abdelmonem Mahmoud
Diagnosis almost certain


Chronic headache.

Patient Data

Age: 25 years
Gender: Female

Right anterior parietal well defined, thin-walled, oval-shaped, extra-axial CSF density cystic lesion measuring 3.3 x 2.5 cm, with remodeling effect on the adjacent bone, it is splaying the overlying inner table of the skull. It exerts a mild mass effect in the form of compression upon the underlying brain parenchyma, no midline shift. No associated edema at the related brain parenchyma.​

Case Discussion

Arachnoid cysts are asymptomatic benign lesions. They are usually located within the subarachnoid space and contain CSF. On imaging, they are characterized as well-circumscribed thin-walled cysts, displacing adjacent structures and following the CSF pattern (hypodense on CT and hyperintense on T2 with FLAIR suppression on MRI). They can also have a remodeling effect on the adjacent bone.

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