ular cysts are most often found in

the atria of the lateral ventricles and foramen of Monro. CPCs

are the most common of all intracranial neuroepithelial cysts,

occurring in up to 50% of autopsies. Most CPCs are actually

xanthogranulomas. Lipid accumulates in the choroid plexus

from degenerating &/or desquamating choroid epithelium.

CPCs are common incidental imaging findings in middle-aged

and older adults. They are usually bilateral and are often

multicystic. Most CPCs are small, measuring 2-8 mm in

diameter. They typically do not suppress completely on FLAIR

and may show moderately high signal intensity on DWI.

Ependymal cysts (ECs) are rare, benign, ependymal-lined cysts

of the lateral ventricles. Most ECs, even large ones, are

asymptomatic and incidental. EC patients presenting with

headache, seizure, &/or obstructive hydrocephalus have been

reported in the literature. They contain clear serous CSF-like

fluid secreted from ependymal cells. ECs typically follow CSF

on all sequences and suppress completely on FLAIR.

CCs occur almost exclusively in the foramen of Monro,

attached to the anterosuperior portion of the 3rd ventricular

roof. They are wedged into the foramen and are typically

straddled by the fornices. CCs are endodermal in origin and

contain viscous gelatinous material consisting of mostly

mucin. CCs may also contain blood degradation products,

foamy cells, and cholesterol crystals. Even relatively small CCs

may suddenly obstruct the foramen of Monro, causing acute

hydrocephalus. Occasionally brain herniation with rapid clinical

deterioration ensues. The imaging appearance of a welldelineated, hyperdense mass at the foramen of Monro on

NECT is virtually pathognomonic of a CC.

Infratentorial intraaxial cysts: Parenchymal infratentorial

cysts are rare; most are PVSs. The only common site is in and

around the dentate nuclei. Most are asymptomatic.

Occasionally, large PVSs occur in the pons and can be a rare

cause of cranial neuropathy.

Nonneoplastic, nonparasitic cysts in the 4th ventricle are

uncommon. The most common cause is not a true cyst but an

enlarged, "encysted" 4th ventricle. Infection or aneurysmal

subarachnoid hemorrhage may cause outlet foraminal

obstruction. When combined with superior obstruction near

the aqueduct, the 4th ventricle can become completely

encysted. Choroid plexus continues to produce CSF. With

egress blocked, the 4th ventricle enlarges. ECs can arise in the

4th ventricle, a much less common posterior fossa location

than the CPA. Some ECs are so similar to CSF that only FLAIR

and DWI permit distinction of an EC from CSF in an enlarged

but otherwise normal-appearing 4th ventricle.

Selected References

1. Aboud E et al: Giant intracranial epidermoids: is total removal feasible? J

Neurosurg. 1-14, 2015

2. Ali M et al: Exploring predictors of surgery and comparing operative

treatment approaches for pediatric intracranial arachnoid cysts: a case series

of 83 patients. J Neurosurg Pediatr. 1-8, 2015

3. Culver SA et al: A Case for conservative management: characterizing the

natural history of radiographically diagnosed Rathke cleft cysts. J Clin

Endocrinol Metab. 100(10):3943-8, 2015

4. Din NU et al: Symptomatic surgically treated non-neoplastic cysts of the

central nervous system: a clinicopathological study from Pakistan. J Coll

Physicians Surg Pak. 25(8):588-91, 2015

5. Kalani MY et al: Pineal cyst resection in the absence of ventriculomegaly or

Parinaud's syndrome: clinical outcomes and implications for patient

selection. J Neurosurg. 1-5, 2015

6. Lauretti L et al: Treatment of giant congenital cysts of the midline in adults:

report of two cases and review of the literature. Surg Neurol Int. 6(Suppl

13):S371-4, 2015

7. Bender B et al: MR imaging findings in colloid cysts of the sellar region:

comparison with colloid cysts of the third ventricle and Rathke's cleft cysts.

Acad Radiol. 20(11):1457-65, 2013

8. Osborn AG et al: Intracranial cysts: radiologic-pathologic correlation and

imaging approach. Radiology. 239(3):650-64, 2006

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Cysts, and Disorders

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