Suprasellar Cystic Mass



Suprasellar Cystic Mass


Anne G. Osborn, MD, FACR



DIFFERENTIAL DIAGNOSIS


Common



  • Enlarged Third Ventricle



    • Obstructive Hydrocephalus


    • Aqueductal Stenosis


  • Arachnoid Cyst


  • Craniopharyngioma


  • Neurocysticercosis (NCC)


Less Common



  • Rathke Cleft Cyst


  • Dermoid Cyst


  • Epidermoid Cyst


  • Enlarged Perivascular Spaces (PVSs)


Rare but Important



  • Pituitary Macroadenoma


  • Pituitary Apoplexy


  • Astrocytoma



    • Pilocytic Astrocytoma


    • Pilomyxoid Astrocytoma


  • Ependymal Cyst


  • Saccular Aneurysm


ESSENTIAL INFORMATION


Key Differential Diagnosis Issues



  • Where does the mass originate?



    • Third ventricle: Think hydrocephalus > intraventricular cystic mass (ependymal cyst, craniopharyngioma)


    • Suprasellar cistern: Arachnoid, other congenital/infectious cysts


    • Pituitary gland/sella turcica: Necrotic/cystic neoplasm


    • Brain parenchyma: Enlarged perivascular spaces, cystic/low density neoplasm


Helpful Clues for Common Diagnoses



  • Enlarged Third Ventricle



    • CSF density/signal intensity


    • No enhancement (unless infection, neoplasm)


    • Obstructive Hydrocephalus



      • Can be intra- or extra-ventricular (noncommunicating or communicating)


      • If acute, periventricular “halo” of transependymal CSF


      • “Cystic mass” = dilated 3rd ventricle


    • Aqueductal Stenosis



      • ↑ Lateral, 3rd ventricles


      • Normal 4th ventricle


      • Usually longstanding, “compensated” so no transependymal CSF


  • Arachnoid Cyst



    • 10% of ACs suprasellar (SSAC)


    • Sharply marginated CSF density/signal intensity mass



      • Suppresses on FLAIR


      • Does not restrict on DWI


    • 3rd ventricle elevated, displaced over AC



      • Displaces temporal lobes laterally


      • Displaces midbrain, pons posteriorly


      • Infundibular stalk typically displaced anteriorly


      • “Mickey mouse ears” on coronal = cyst + lateral ventricles


    • If large, may also cause obstructive hydrocephalus


  • Craniopharyngioma



    • 90% of childhood craniopharyngiomas cystic



      • Cyst fluid hyperdense/intense to CSF


    • 90% have some Ca++ (globular or rim)


    • 90% enhance (rim, nodular)


    • Suprasellar cistern > > within 3rd ventricle


  • Neurocysticercosis (NCC)



    • Look for “clusters” of cysts in subarachnoid cisterns (“racemose” NCC)


    • Look for cyst + scolex


    • FLAIR best sequence to detect (cyst fluid doesn’t suppress completely)


Helpful Clues for Less Common Diagnoses



  • Rathke Cleft Cyst



    • 60% purely suprasellar or intrasellar with suprasellar extension


    • Variable density/signal intensity



      • Usually ↑ compared to CSF


      • 10% calcify (curvilinear, in cyst wall)


    • Look for



      • Intracystic nodule (45%)


      • “Claw” of compressed, enhancing pituitary displaced around cyst


  • Dermoid Cyst



    • Most common site = sellar/parasellar, frontonasal


    • Fat density/signal intensity


    • 20% have capsular Ca++


    • Look for evidence of rupture



      • Fat droplets in subarachnoid spaces


      • Fat-fluid levels in ventricles


      • Chemical shift artifact in frequency encoding direction



  • Epidermoid Cyst



    • Rare in suprasellar cistern


    • Lobulated, insinuating growth pattern


    • > 95% hypodense (similar to CSF)



      • FLAIR, DWI best to distinguish epidermoid from AC, enlarged 3rd ventricle


      • Epidermoid doesn’t suppress completely, restricts on DWI


  • Enlarged Perivascular Spaces (PVSs)



    • Usually variable-sized “clusters”


    • Off-midline (basal ganglia)


    • Round or ovoid (basal ganglia), linear (white matter)


    • Like CSF on all sequences (contain interstitial fluid)



      • Suppresses completely on FLAIR


      • Does not restrict on DWI


Helpful Clues for Rare Diagnoses



  • Pituitary Macroadenoma



    • Solid ± intra- or extratumoral cysts



      • Extratumoral cysts may be trapped/enlarged PVSs or arachnoid cysts


      • Cysts often hyperdense/intense compared to CSF


    • Solid > rim enhancement


  • Pituitary Apoplexy



    • Rare; may be life-threatening (severe panhypopituitarism)


    • Necrotic pituitary with little/no enhancement (may show rim)


    • Hemorrhage may bloom on T2* (GRE, SWI)


    • Compression/edema of hypothalamus, optic chiasm/tracts may cause hyperintensity on T2WI


    • Restricts on DWI


    • Markedly hypointense on ADC


  • Astrocytoma



    • Pilocytic > > pilomyxoid astrocytoma


    • Most suprasellar astrocytomas are solid, not grossly cystic


  • Ependymal Cyst



    • Rare; 3rd ventricle least common site


    • Round/ovoid; CSF-like


  • Saccular Aneurysm



    • Aneurysms may be associated with true perianeurysmal cysts



      • Obstructed perivascular spaces posited as etiology


    • Partly or completely thrombosed may have “cystic”-appearing foci within clot



      • Rare


      • Acute thrombosis can present with panhypopituitarism, SAH


    • Imaging can mimic necrotic adenoma



      • Hypodense center, iso-/hyperintense rim on T1WI


      • Look for mixed age laminated clot


      • “Blooms” on GRE


      • Rim may enhance






Image Gallery









Sagittal T2WI MR shows EVOH with markedly enlarged lateral image, 3rd image, and 4th image ventricles. A CSF suprasellar mass caused by an enlarged 3rd ventricle was diagnosed.

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Aug 7, 2016 | Posted by in NEUROLOGY | Comments Off on Suprasellar Cystic Mass

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