Primary Nonneoplastic Cysts Overview
an autopsied case of a colloid
cyst, sectioned in the coronal
Monro. Note the gelatinousappearing lobulated cyst
with the fornices st straddling
the cyst. This patient died of
middle cranial fossa. The cyst
within split layers of arachnoid
(Left) Gross surgical specimen
shows the characteristic lining
appears similar to neurenteric
Primary Nonneoplastic Cysts Overview
Intracranial Cystic-Appearing Lesions
Rathke cleft cyst Porencephalic cyst
Arachnoid cyst (suprasellar) Connatal, germinolytic cysts
Arachnoid cyst (middle cranial fossa, convexity) Choroid plexus cysts
Epidermoid cyst Ependymal cyst
TACs (macroadenoma, meningioma) Colloid cyst
Leptomeningeal cyst ("growing fracture")
Neurenteric cyst Enlarged PVSs (dentate nuclei)
Epidermoid (CPA) Epidermoid (4th ventricle, cisterna magna)
Arachnoid cyst (CPA) Cystic ("trapped") 4th ventricle
Intracranial Cysts by Type, Most Common Location(s)
Arachnoid cyst Middle cranial fossa, CPA, suprasellar cistern
Choroid fissure cyst Choroid fissure, between temporal horn and suprasellar cistern
Choroid plexus cyst Choroid plexus glomus
Colloid cyst Interventricular foramen/anterosuperior 3rd ventricle
Connatal cyst(s) Peri- or intraventricular, adjacent to frontal horn, body of lateral ventricle
Dermoid cyst Suprasellar, frontonasal (anteroinferior interhemispheric fissure)
Enlarged PVSs Basal ganglia, midbrain, cerebral white matter, dentate nuclei
Ependymal cyst Lateral ventricle (atrium most common)
Germinolytic pseudocyst(s) Periventricular, subependymal along caudothalamic groove
Hippocampal sulcus remnants Hippocampus, just medial to lateral ventricle
Leptomeningeal cyst ("growing fracture") Parietal bone
Neurenteric cyst Prepontine at pontomedullary junction
Neuroglial cyst Frontal/temporal subcortical white matter, choroid fissure
Porencephalic cyst Cerebral hemispheres, adjacent to lateral ventricles
Rathke cleft cyst Suprasellar, intrasellar
Sebaceous (trichilemmal) cyst Scalp (dermis or subcutaneous tissues)
Tumor-associated cyst Between schwannoma, meningioma, macroadenoma, and brain
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
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
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.
1. Aboud E et al: Giant intracranial epidermoids: is total removal feasible? J
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
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
