Last Updated: September 6, 2020
- Mucin-containing unilocular third-ventricular cyst often located near the foramen of Monro
- Synonymous terms: paraphyseal or neuroendodermal cyst
- Congenital abnormality due to ependymal encystment or persistence of the paraphysis
- Thin fibrous capsule of simple or pseudostratified epithelium with goblet and ciliated cells
- Center filled with mucin, cholesterol, and desquamated epithelium
- Most common during third and fouth decades of life
- Uncommon in children
- No gender predilection
- Majority are stable in size and without ventricular obstruction
- Minority continue to enlarge, causing intraventricular obstructive hydrocephalus ± coma, death
- Common presenting signs/symptoms
- Small cysts: positional headache
- Larger obstructing cysts: sudden-onset hydrocephalus with herniation, coma, and sudden death
- Treatment: surgical resection, cerebrospinal fluid (CSF) shunting
- Well-marginated hyperdense unilocular cyst arising within anterior third ventricle near the foramen on Monro (99%)
- Forniceal pillars elevated over cyst
- Size variable
- Majority are hyperdense due to high proteinaceous content
- No enhancement on contrast-enhanced CT imaging
- T1WI: isointense to hyperintense due to cholesterol content
- T2WI: variable signal intensity
- FLAIR: hyperintense
- DWI: no diffusion restriction
- T1WI+C: no enhancement
- Nonenhanced head CT, MRI without and with intravenous contrast (to exclude mimics); serial imaging follow-up for small cysts without hydrocephalus
For more information, please see the corresponding chapter in Radiopaedia.
Contributor: Rachel Seltman, MD
Demirci S, et al. Sudden death due to a colloid cyst of the third ventricle: report of three cases with a special sign at autopsy. Forensic Sci Int 2009;189:e33–e36.
El Khoury C, et al. Colloid cysts of the third ventricle: are MR imaging patterns predictive of difficulty with percutaneous treatment? AJNR Am J Neuroradiol 200021:489–492.
Osborn A G, Salzman KL, Jhaveri MD. (2016). Diagnostic Imaging (3rd ed). Philadelphia, PA: Elsevier, 2016.
Sheikh AB, et al. Endoscopic versus microsurgical resection of colloid cysts: a systematic review and meta-analysis of 1,278 patients. World Neurosurg 2014;82:1187–1197.
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