Case of the Week - Patient Summary 1022Peer Reviewed and Certified -
Epidermoid Inclusion Cyst
Enlarged Subarachnoid Space
Arachnoid Cyst The contents are very similar to CSF (spinal fluid) in chemical composition. Therefore, the attenuation (on CT) and the signal intensity (on MR) are usually identical to CSF.
The most common location for an intracranial arachnoid cyst is the middle cranial fossa - typically lateral to the temporal lobe and adjacent to the temporal tip and/or insular cortex.
Intrasellar CSF usually occurs as "empty sella syndrome" - the result of herniation of the subarachnoid space into the pituitary fossa. This is most often seen in middle-aged women, and is thought to be caused by multiple pregnancies (physiologic pituitary hypertrophy dilates the opening in the diagphragma sella that admits the pituitary stalk).
