Primary Nonneoplastic Cysts Overview

Intracranial Cystic-Appearing Lesions

Extraaxial Intraaxial

Supratentorial Supratentorial

Midline Parenchymal

Pineal cyst Enlarged PVSs

Dermoid cyst Neuroglial cyst

Rathke cleft cyst Porencephalic cyst

Arachnoid cyst (suprasellar) Connatal, germinolytic cysts

Hippocampal sulcus remnants

Off midline Intraventricular

Arachnoid cyst (middle cranial fossa, convexity) Choroid plexus cysts

Epidermoid cyst Ependymal cyst

TACs (macroadenoma, meningioma) Colloid cyst

Sebaceous cyst (scalp)

Leptomeningeal cyst ("growing fracture")

Infratentorial Infratentorial

Midline Parenchymal

Neurenteric cyst Enlarged PVSs (dentate nuclei)

Arachnoid cyst

Off midline Intraventricular

Epidermoid (CPA) Epidermoid (4th ventricle, cisterna magna)

Arachnoid cyst (CPA) Cystic ("trapped") 4th ventricle

TACs (schwannoma, meningioma)

Nonneoplastic, noninfectious cystic brain lesions are classified by common anatomic locations. The 1st division is extra- vs. intraaxial, then supra- vs.

infratentorial. Extraaxial cysts are further subdivided into midline and off midline lesions. Intraaxial cysts are subdivided into parenchymal and

intraventricular. CPA = cerebellopontine angle; PVSs = perivascular (Virchow-Robin) spaces; TACs = tumor-associated cysts.

Intracranial Cysts by Type, Most Common Location(s)

Cyst Type 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

Epidermoid cyst CPA

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

Pineal cyst Pineal gland

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

Cysts, and Disorders

Brain: Pathology-Based Diagnoses: Neoplasms,

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