|Case of the Week - Patient Summary 1022|
Peer Reviewed and Certified -
|Demographics: 31 y.o. man|
|History & Chief complaint:|
| Chronic headache |
|Physical exam and Laboratory:|
| Normal |
|Summary of Findings:|
|Fluid like signal intensity in the basilar cisterns - much larger than the normal subarchnoid space.|
Epidermoid Inclusion Cyst
Enlarged Subarachnoid Space
| Arachnoid Cyst |
|Treatment and Followup:|
|Several months later, the patient developed hypopituitary signs and symptoms. At that time a cisternogram confirmed free communication of CSF into the suprasellar cistern.|
|An arachnoid cyst is a fluid filled enclosed space lined by arachnoid cells. Some prefer the term "intra-arachnoid" cyst, since the cyst wall itself is usually between leaves of arachnoid tissue - instead of within the subarachnoid space (pia - arachnoid).
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).