CNS & pituitary tumors
Cysts
Arachnoid cyst
Author: Eman Abdelzaher, M.D., Ph.D.
Last author update: 1 February 2012
Last staff update: 9 March 2023 (update in progress)
Copyright: 2002-2023, PathologyOutlines.com, Inc.
PubMed Search: CNS arachnoid cyst
Table of Contents
Definition / general | Sites | Etiology | Clinical features | Radiology description | Radiology images | Case reports | Treatment | Gross description | Microscopic (histologic) description | Positive stains | Negative stainsCite this page: Abdelzaher E. Arachnoid cyst. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/cnstumorarachnoidcyst.html. Accessed March 22nd, 2023.
Definition / general
- Benign subarachnoid accumulation of CSF of congenital origin (Rev Neurol 2004;39:1161)
- 1% of intracranial masses
- Arachnoid cysts may be discovered in utero (by ultrasound screening) or be discovered during childhood or adulthood
Sites
- Arise within both cranial and spinal meninges
- Expand at expense of brain or spinal cord
- Favored intracranial sites include middle fossa near temporal lobe and cerebellopontine angle
Etiology
- Congenital lesions that arise from reduplication or splitting of leptomeninges
- Sporadic or associated with other malformations or diseases
Clinical features
- Depends on size and location
- Symptoms more common in middle fossa cysts; include headache and seizures
Radiology description
- MRI distinguishes between CSF contents and lipid rich contents of epidermoid and dermoid cysts
Radiology images
Images hosted on other servers:
MR: arachnoid cyst
Various images
Case reports
- 27 week fetus (Radiology 1999;211:609)
Treatment
- Surgery if symptomatic
Gross description
- Variable size but may be vary large
- Thin transparent wall with clear, colorless fluid
- Cyst is distinct from leptomeninges and dura
Microscopic (histologic) description
- Cyst wall formed of delicate fibrous connective tissue lined by meningothelial cells (diffuse or focal)
Positive stains
- Meningothelial cells are positive for EMA
Negative stains
- Meningothelial cells are negative for CK, GFAP, transthyretin and synaptophysin
