Vermis Mass



Vermis Mass


Gregory L. Katzman, MD, MBA



DIFFERENTIAL DIAGNOSIS


Common



  • Medulloblastoma (PNET-MB)


  • Pilocytic Astrocytoma


Less Common



  • Metastasis


  • Hemangioblastoma


Rare but Important



  • Dural A-V Fistula


  • Arteriovenous Malformation


  • Cavernous Malformation


  • Cerebellitis


  • Atypical Teratoid-Rhabdoid Tumor


  • Dermoid Cyst


  • Glioblastoma Multiforme


  • Ganglioglioma


  • Dysplastic Cerebellar Gangliocytoma


  • Rhombencephalosynapsis (Mimic)


ESSENTIAL INFORMATION


Key Differential Diagnosis Issues



  • Patient age



    • Child: PNET-MB, pilocytic astrocytoma (PA), ATRT most common


    • Adult: Metastasis, hemangioblastoma most common


  • Does mass originate in vermis or 4th ventricle (V)?



    • Vermis: PA, metastasis, hemangioblastoma, cerebellitis, ATRT


    • 4th ventricle: PNET-MB (from superior medullary velum), ATRT


Helpful Clues for Common Diagnoses



  • Medulloblastoma (PNET-MB)



    • 30-40% of childhood infratentorial tumors


    • Round, hyperdense 4th ventricle mass



      • Arises from 4th ventricle roof


      • Posteroinferior spread into cisterna magna


      • Distinguishes PNET-MB from ependymoma (arises from floor, extrudes laterally)


      • Look for early subarachnoid spread


    • Lateral cerebellar hemisphere location



      • Desmoplastic variant


      • More common in older children, adults


  • Pilocytic Astrocytoma



    • Cystic mass with enhancing mural nodule


    • Hemispheres > vermis


    • Ca++ 20%, hemorrhage rare


Helpful Clues for Less Common Diagnoses



  • Metastasis



    • ALWAYS include metastasis in differential diagnosis of posterior fossa parenchymal mass in adult!



      • Seen in 25% of cancer patients at autopsy


      • Location approximately 80% hemispheres, 15% vermis, 5% pons/midbrain


    • Metastases have rounded configuration



      • Usually displace rather than infiltrate tissue


      • Virtually 100% enhance


      • Variable edema


    • Can be hematogenous or originate from leptomeningeal carcinomatosis


  • Hemangioblastoma



    • Adult with intra-axial posterior fossa mass = metastasis vs. hemangioblastoma



      • Classic imaging of hemangioblastoma = cyst + enhancing mural nodule abutting pia


      • Solid mass ± hemorrhage less common


      • Size varies (tiny to several centimeters)


    • Only 1-2% of 1° intracranial tumors but 7-10% of posterior fossa tumors



      • 80% cerebellar hemispheres


      • 15% vermis, 5% other (medulla, 4th V)


    • ± von Hippel-Lindau syndrome



      • Hemangioblastomas in VHL typically don’t develop until young adulthood, middle age


      • Rare in children


Helpful Clues for Rare Diagnoses



  • Dural A-V Fistula



    • 10-15% of all cerebrovascular malformations


    • Dural AVF involving foramen magnum, tentorium, torcula Herophili, or posterior fossa veins (e.g., inferior vermian vein) may affect vermis


    • May be occult, cause tinnitus


    • Can present with hemorrhage


    • Rare: Dementia


  • Arteriovenous Malformation



    • “Bag of black worms” on MR with minimal/no mass effect unless hemorrhage


    • Posterior fossa < hemispheres



    • Headache, hemorrhage in 50%


  • Cavernous Malformation



    • Benign vascular hamartoma with masses of immature blood vessels (“caverns”), intralesional hemorrhages, no neural tissue


    • Seizure 50%, neurologic deficit 25%, asymptomatic 20%


    • NECT: 40-60% Ca++


    • MR



      • Most common pattern = “popcorn ball” with hypointense rim


      • May present initially with large hematoma


    • Can be familial, multiple (multiple cavernous malformation syndrome)



      • Do T2* scan (GRE or SWI) in all cases of spontaneous, “unexplained” intracranial hemorrhage!


  • Cerebellitis



    • Rare inflammatory syndrome



      • Can be primary infectious, post-infectious, post-vaccination, or idiopathic


    • Imaging often nonspecific


    • MR > > CT



      • Bilateral hemispheric involvement (75%)


      • T2 hyperintensity


      • Variable enhancement (none to intense)


  • Atypical Teratoid-Rhabdoid Tumor



    • Infant/young child


    • 50% infratentorial


    • Off-midline > vermis


    • Mass often large, heterogeneous


    • Can mimic PNET-MB


  • Dermoid Cyst



    • Rare: < 0.5% of 1° intracranial tumors


    • Fat appearance: Use fat-suppressed sequence to confirm


    • With rupture find fat droplets in cisterns, sulci, ventricles w/extensive enhancement possible from chemical meningitis


  • Glioblastoma Multiforme



    • Rapidly enlarging tumor with necrosis, neovascularity


    • Peak 45-70 years but may occur at any age


    • Cerebellum uncommon primary site


    • 95% have thick, irregular enhancing rind of neoplastic tissue surrounding necrotic core


  • Ganglioglioma



    • Well-differentiated, slowly growing neuroepithelial tumor composed of neoplastic ganglion cells & glial cells


    • Partially cystic, enhancing, cortically based mass in child or young adult


    • Hemispheres > > cerebellum


    • Ca++ common (35-50%)


  • Dysplastic Cerebellar Gangliocytoma

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