Cystic CPA Mass



Cystic CPA Mass


H. Ric Harnsberger, MD



DIFFERENTIAL DIAGNOSIS


Common



  • Epidermoid Cyst, CPA-IAC


  • Arachnoid Cyst, CPA-IAC


Less Common



  • Vestibular Schwannoma with Intramural Cyst(s)


  • Neurocysticercosis, CPA


  • Hemangioblastoma


  • Large Endolymphatic Sac Anomaly (IP-2)


Rare but Important



  • Vestibular Schwannoma with Arachnoid Cyst


  • Schwannoma, Facial Nerve, CPA-IAC with Cyst


  • Neurenteric Cyst


  • Schwannoma, Jugular Foramen with Intramural Cyst


ESSENTIAL INFORMATION


Key Differential Diagnosis Issues



  • This differential diagnosis is constructed around lesions of CPA that may have cystic manifestation



    • Lesions that are characteristically cystic include: Epidermoid cyst, arachnoid cyst, neurocysticercosis, large endolymphatic sac anomaly & neurenteric cyst


    • Many of solid CPA tumors may have either intramural cysts, necrosis or extramural cysts as normal or variant MR imaging manifestation



      • Schwannoma: Vestibular, facial nerve or jugular foramen schwannoma with intramural or extramural/arachnoid cyst can all be found in CPA area


      • Cystic meningioma


      • Hemangioblastoma


  • Idealized imaging protocol in evaluating cystic CPA mass lesions



    • T1 C+ fat-saturated MR is gold standard



      • Contrast helps differentiate solid from cystic components of tumors such as vestibular or facial nerve schwannoma, meningioma & hemangioblastoma


      • Use DWI sequence for possible epidermoid (restricted diffusion)


    • T2 thin-section high-resolution MR



      • Also sorts out solid and cystic components of lesions


      • May help with associated cranial nerve and arterial anatomy


Helpful Clues for Common Diagnoses



  • Epidermoid Cyst, CPA-IAC



    • Congenital rest of epithelial tissue in CPA


    • Imaging



      • Insinuating ± scalloping brainstem margin


      • T1 C+ MR: Nonenhancing, cystic appearing; may be difficult to see


      • DWI: Restricted diffusion (high signal) makes diagnosis


  • Arachnoid Cyst, CPA-IAC



    • Congenital lesion resulting from failure of embryonic meninges to merge with cyst between split in arachnoid membrane


    • Imaging: Fills cistern with rounded margins



      • T1 C+ MR: No enhancement


      • Other MR: FLAIR attenuates; DWI: No restricted diffusion


Helpful Clues for Less Common Diagnoses



  • Vestibular Schwannoma with Intramural Cyst(s)



    • Vestibular schwannoma may have either intramural or extramural (arachnoid cyst) cysts


    • Imaging



      • Solid CPA-IAC mass with intramural cysts


      • T1 C+ MR: Enhancing solid tumor component ± intramural cysts (common) ± arachnoid cyst (rare)


  • Neurocysticercosis, CPA



    • Intracranial infection caused by pork tapeworm (Taenia solium)


    • Imaging



      • Cysts with “dots” inside


      • Appearance varies with stage


      • T1 C+ MR: Cysts with enhancing thin or thick wall


  • Hemangioblastoma



    • Adult with intra-axial posterior fossa mass abutting pia


    • Imaging



      • Cerebellar cystic & solid tumor


      • T1 C+ MR: 60% of tumors with solid enhancing & cystic components (40% solid only)



  • Large Endolymphatic Sac Anomaly (IP-2)



    • Bilateral congenital SNHL that appears in child with cascading hearing loss pattern


    • Most common congenital imaging abnormality


    • Imaging



      • CT: Enlarged bony vestibular aqueduct


      • T2 high-resolution MR: Enlarged endolymphatic sac + mild cochlear aplasia (modiolar deficiency, bulbous apical turn, scalar chamber asymmetry)


Helpful Clues for Rare Diagnoses

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

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