Guide to intracranial cysts: A “Cyst-o-matic” approach Bryan Foley MD, Jennifer Becker MD, Rihan Khan,MD

Control #: 680 Title: Intracranial cystic lesions: A “cyst-o-matic” approach to identification with pathologic correlation eEdE#: eEdE-63

Disclosures None

Purpose: The purpose of this exhibit is to provide an interactive case based review of intracranial cystic lesions with a focus on CT and MR, while discussing the etiologies and differential diagnostic considerations.   Approach/Methods: We present a spectrum of intracranial cystic lesions and interesting variants from cases collected over the last 3 years from everyday neuroradiology practice at a university medical center.

Characterizing an intracranial Cyst Location + CT or MR imaging features = Diagnosis or short Differential Diagnosis

Anatomic Location Intra-axial Extra-axial Supra or infratentorial Midline Off-Midline

Findings/Discussion:   Cases will be presented demonstrating common and uncommon intracranial cysts and cystic lesions. First you will see the images, next an image description locating the cyst, then a summary slide with key facts and differential diagnosis.

The most Common extra-axial CYst Arachnoid Cyst Extra-axial, supratentorial, off-midline cyst that follows CSF signal, no restricted diffusion

Arachnoid cyst Benign congenital lesion, lined by arachnoid cell single layer Extraaxial, conforms around brain parenchyma Most are supratentorial and off-midline Contain clear fluid that follows CSF signal Uniclocular, smooth wall, can remodel the calvarium No restricted diffusion, No enhancement Typically supratentorial, middle cranial fossa ~65% Posterior fossa ~10% Treatment options: observe, resection, shunting Hemorrhage into cyst can rarely occur Classic Uncommon DDX Epidermoid cyst (+DWI) Porencephalic cyst (communicates with ventricle) Chronic subdural hematoma (old blood products GRE or SWI)

Arachnoid cyst Rare midline arachnoid cyst assumed in the velum interpositum

Epidermoid cyst Extra-axial, basal cistern, para-midline cystic mass, CT hypodense, MR restricted diffusion and incomplete FLAIR suppression

Epidermoid cyst Congenital Squamous epithelium wall with internal keratin and cholesterol Location: Extra-axial, paramidline, basal cisterns Cerebellopontine angle CPA cistern ~50% Fill cisterns, surround vessels and cranial nerves CT: hypodense similar to CSF MR: + DWI restriction, T1 T2 iso to hyperintense, mild heterogeneity, incomplete FLAIR suppression , minimal–no enhancement DDX Arachnoid cyst, (no DWI, CSF signal) Dermoid cyst, (midline, less common, fat T1 signal)

Epidermoid cyst Incidental finding of an intracranial extra-axial, lesion just above the right foramen ovale that is consistent with an incidental epidermoid cyst.

Dermoid cyst Extra-axial, suprasellar, midline cystic mass T1 hyperintense (fat) , FLAIR intense, +DWI

Dermoid cyst Benign, congenital Keratin + cholesterol + hair, fat, oil Midline, suprasellar cistern location most common Rare, younger age than epidermoid Can rupture, chemical meningitis CT: hypodense MR: fat T1 signal, +DWI, FLAIR intense DDX Epidermoid cyst, (no fat signal) Lipoma (homogeneous) Craniopharyngioma (multicystic, enhancement)

Enlarged perivascular Space T2 cyst Intra-axial, supratentorial, follows CSF signal, no enhancement, No restricted diffusion

Enlarged perivascular Space AKA “Virchow-Robin space Most common intra-axial cyst Anatomic variant, nonneoplastic Dilated pia lined spaces along arterioles into brain parenchyma (intra-axial) Follow CSF signal Classic located near the anterior commisure in basal ganglia Also common in white matter, midbrain, and cerebellum dentate nuclei (*infratentorial) Incidental, usually asymptomatic DDX Lacunar infarct Neurocysticercosis

Neuroglial cyst Intra-axial, supratentorial, follows CSF signal, no enhancement, No restricted diffusion There is no restricted diffusion, internal or peripheral enhancement, solid components, or surrounding vasogenic edema. The cyst does not communicate with the adjacent right lateral ventricle or extend to the right frontal cortex. Imaging findings are consistent with a Neuroglial cyst

Neuroglial cyst Benign congenital lesion Uncommon Intra-axial Clear CSF like cyst lined by epithelium Typically intraparenchymal in the frontal lobe Round, smooth, no enhancement, Does not communicate with the ventricle DDX Enlarged perivascular space Infectious cyst Arachnoid cyst Cystic neoplasm Companion case of a left temporal lobe Neuroglial cyst

Choroid plexus cyst Intra-axial, intra-ventricular subtle CSF density and T2 hyperintense cystic masses with peripheral enhancement in the choroid plexus glomi in the lateral ventricle atria. Imaging findings consistent with Choroid Plexus Cysts.

Choroid plexus cyst Benign, congenital and acquired Location: intraventricular, choroid glomus in atrium Usually asymptomatic and incidental, rarely can cause hydrocephalus obstruction with large size Cyst contains protein; CT and MR signal vary iso to hyper T1 and T2, variable enhancement ~75% bright on DWI enhancement DDX Ependymal cyst Choroid plexus papilloma (child, avid enhancement) Acute stroke workup demonstrating incidental choroid plexus cysts on DWI

Colloid cyst Intra-axial, intra-ventricular unilocular hyperdense cyst at the upper 3rd ventricle/foramen of Monroe area. MR demonstrates isointense T2 signal and nonenhancment. No acute hydrocephalus.

Colloid cyst Unilocular 3rd ventricle mucin containing cyst derived from endoderm Characteristic location: antero-superior aspect of the third ventricle, adjacent to the Foramen on Monro and between the fornices Symptoms asymptomatic/incidental to headache and obstructive hydrocephalus CT majority are hyperdense MR signal variable depending on protein and water content, No restricted diffusion Size subcentimeter – 3 cm Treatment: surgical excision Notify physician about findings b/c risk of hydrocephalus and death DDX Characteristic location limited differential Intraventricular metastasis Astrocytoma

Etra-axial, supratentorial, midline cyst in pineal gland Pineal cyst Etra-axial, supratentorial, midline cyst in pineal gland

Pineal Cyst Benign, fluid cyst in pineal gland Etiology unknown Incidental finding, relatively common ~25% of adults Usually asymptomatic Large cyst can compress cerebral aqueduct and cause hydrocephalus or compress midbrain tectum (Perinaud syndrome) Rarely hemorrhage complication Small <1 cm Signal intensity variable but usually iso to hyperintense to CSF DDX Pineocytoma (solid, enhancement)

Extra-axial, supratentorial, midline T2 hyperintese cyst in the sella Rathke cleft Cyst Extra-axial, supratentorial, midline T2 hyperintese cyst in the sella

Rathke Cleft Cyst Usually incidental and asymptomatic DDX Congenital lesion of residual Rathke’s pouch between the anterior and intermediate pituitary lobes Usually incidental and asymptomatic Hemorrhage complication is rare Sellar and suprasellar mass effect Symptoms: asymptomatic or related to mass effect, headache, pituitary dysfunction, visual field deficits Well circumscribed sellar based cyst usually T2 hyperintense based on protein content No enhancement, peripheral enhancement represents compressed pituitary DDX Craniopharyngioma Pituitary adenoma Arachnoid cyst

Porencephalic cyst Intra-axial, supratentorial, off-midline CSF cystic cavity that communicates with the ventricles Congenital or acquired CSF cystic cavity that communicates with the ventricles Follow CSF signal and density

Porencephalic cyst DDX Arachnoid cyst (extraaxial) CSF filled cavity in the brain parenchyma Majority are acquired from prior insult but can be congenital Communicate with or adjacent to the ventricle Follow CSF signal, sharp margins, No restricted diffusion DDX Arachnoid cyst (extraaxial) Cystic encephalomalacia

Intracranial abscess Intra-axial, supratentorial, off-midline frontal lobe low density ring enhancing mass with restricted diffusion, surrounding vasogenic edema ,and mass effect . Findings consistent with …

Intracranial abscess Rare Appearance of infection depends on stage early/late cerebritis stage, early/late capsule stage Commonly supratentorial at grey-white junction Restricted diffusion (+DWI) and presentation (headache, fever) Etiology depends on age and immune status, most are hematogenous and pyogenic Treatment: surgical excision and drainage + antibiotics DDX “Ring-enhancing mass” Cystic neoplasm 1° or metastatic Subacute hematoma or infarction Demyelinating process

neurocysticercosis Extra-axial, supratentorial, off-midline temporal lobe T2 hyperintense cyst with central enhancing scolex, thin enhancing wall, and absent surrounding vasogenic edema

Neurocysticercosis Most common CNS parasitic infection Caused by the encysted larva of the tapeworm Taenia solium Common worldwide and the Southwest United States Extraaxial, cyst actually in the subarachnoid space but can appear intraparenchymal Multiple stages: vesicular, colloid, granular, calcified Early vesicular stage can present as an intracranial cyst DDX Malignancy, cystic metastasis Enlarged perivascular space Left temporal lobe vesicular stage cyst with scolex

Craniopharyngioma Extra-axial, suprasellar, midline T2 hyperintense cystic sella/suprasellar mass causing obstructive hydrocephalus

craniopharyngioma Benign, WHO 1 epithelial tumor from Rathke pouch Extra-cranial cystic suprasellar mass Usually T2 hyperintense Wall and solid components enhance Look for a calcification Bimodal distribution children, adults 2 types - Adamantinomatous: cystic pediatric type - Papillary: solid adult type Treatment: resection, radiation DDX Dermoid (T1 fat signal, +DWI, no enhancement) Rathke cleft cyst

Cystic brain metastasis Colon adenocarcinoma

Hemangioblastoma

Cystic Schwannoma

Summary/Conclusion:  We reviewed common and uncommon intracranial cysts. Start with anatomic localization of a cyst first (intra/extra axial, midline, intraventricular?) CT and MR imaging features (CSF signal, diffusion, enhancement) Combine location and appearance to make diagnosis or form a short differential.

references Osborn AG, Preece MT. Intracranial Cysts: Radiologic-Pathologic Correlation and Imaging Approach.Radiology 2006:239:650-664 Lerner A, Shiroisho MS, Zee C, Law M, et al. Imaging of Neurocysticercosis. Neuroimaging Clin N Am 2012:22:659-76 Armao D, Castillo M, Chen H, et al. Colloid Cyst of the Third Ventricle: Imaging-pathologic Correlation. AJNR Am J Neuroradiol 2000:21:1470–77 Salzman KL, Osborn AG, House P et-al. Giant tumefactive perivascular spaces. AJNR Am J Neuroradiol. 2005:26:298-305 Harrison MJ, Morgella S, Post KD. Epithelial cystic lesions of the sellar and parasellar region: a continuum of ectodermal derivatives? J Neurosurg 1994:80:I018-25 Osborn, AG Intracranial Cysts In: Diagnostic Imaging Brain. Salt Lake City, Utah: Amrsys, 2013; 773-808.