Arachnoid Cyst Characteristics and Diagnosis

Imaging Characteristics

Arachnoid cysts are thin-walled sacs filled with clear CSF fluid that is isodense with normal CSF on imaging studies 1
On MRI, these cysts appear isointense to CSF on all sequences, with no enhancement after gadolinium administration 2
The MRI protocol for diagnosis should include standard T1- and T2-weighted sequences 1
Fluid-attenuated inversion recovery sequences are also recommended for diagnosis 2
Arachnoid cysts may exhibit mass effect on adjacent brain tissue 2

"Giant" cysts (>50mm in diameter) are occasionally found in the Sylvian fissure, which includes the opercular region 2