T1/T2 Hyperintense Parenchymal Lesions



T1/T2 Hyperintense Parenchymal Lesions


Anne G. Osborn, MD, FACR



DIFFERENTIAL DIAGNOSIS


Common



  • Intracerebral Hematoma


  • Cavernous Malformation


  • Cerebral Amyloid Disease


Less Common



  • Multiple Sclerosis


  • Neurofibromatosis Type 1


  • Metastases, Parenchymal


  • Cerebral Infarction, Subacute


Rare but Important



  • Lymphoma, Primary CNS


  • Lipoma


  • Fahr Disease


ESSENTIAL INFORMATION


Key Differential Diagnosis Issues



  • While many CNS parenchymal lesions are hyperintense on T2WI, few also demonstrate T1 shortening (hyperintensity)


  • Lesions with intrinsic T1 shortening on nonenhanced scans



    • Fat


    • Blood (subacute hemorrhage)


    • Proteinaceous fluid collections


    • Melanin


    • Calcification


    • Flow phenomena


  • Does lesion with T1 shortening represent hemorrhage?



    • Subacute hemorrhage with extracellular methemoglobin shows T1 shortening, T2 prolongation


    • Use T2* scan (GRE/SWI)



      • Detects field inhomogeneity


      • Initially shows hypointense margin; critical feature differentiating hemorrhage from other hyperintense masses during early stages


Helpful Clues for Common Diagnoses



  • Intracerebral Hematoma



    • Hematoma staging based on signal characteristics



      • After hyperacute period, clot contains intracellular deoxyhemoglobin sequestered within intact RBCs


      • Signal change proceeds peripherally to centrally


      • Rim “ages” faster than center


    • Early subacute parenchymal hemorrhage



      • Typically 3-6 days


      • Contains methemoglobin within RBCs


      • T1 shortening in periphery


      • Isointense centrally


      • Profound T2 hypointensity


    • Late subacute/early chronic hemorrhage



      • Cells lyse, release methemoglobin


      • Extracellular dilute free methemoglobin demonstrates diffuse T1 shortening, T2 prolongation


      • Hematoma demonstrates hyperintensity on both T1/T2WI


      • Develops hypointense rim


  • Cavernous Malformation



    • Zabramski type 1 = subacute hemorrhage



      • Hyperintense on T1WI


      • T2 signal depends on hematoma stage


      • Early subacute: Hypointense on T2WI


      • Late subacute: Hyperintense on T2WI


    • Zabramski type 2 = mixed signal (classic “popcorn” ball)



      • Fluid-fluid levels in multiple “caverns”


      • Iso-/hyperintense on T1WI


      • Hypo-/hyperintense on T2WI


      • Complete T2-hypointense hemosiderin rim surrounds lesion


      • Important: Do T2* scan (GRE/SWI) to look for multiple lesions


  • Cerebral Amyloid Disease



    • Elderly normotensive demented patient


    • Look for multiple parenchymal hemorrhages of different ages



      • Subacute hematomas are hyperintense on both T1/T2WIs


      • Do T2* sequence!


      • > 50% have multiple cortical/subcortical “black dots” (microhemorrhages)


      • CAA microbleeds rare in cerebellum, basal ganglia (typical for chronic hypertensive encephalopathy)


Helpful Clues for Less Common Diagnoses



  • Multiple Sclerosis



    • Most MS plaques are hypointense on T1WI, hyperintense on T2WI


    • Chronic plaques may develop faint hyperintense “ghost” or “rim” on T1WI that surrounds hypointense lesions


    • Deep periventricular white matter most common location



  • Neurofibromatosis Type 1



    • Bilateral basal ganglia hyperintensity common in NF1


    • Foci of abnormal signal intensity (“FASIs”) on T2WI represent myelin vacuolization, clumping, disappear with age


  • Metastases, Parenchymal



    • Most are iso-/hypointense on T1WI


    • T2 signal intensity variable


    • Metastases with subacute hemorrhage or melanin may display T1 shortening


  • Cerebral Infarction, Subacute



    • Hemorrhagic transformation



      • Typically occurs between 2-5 days


      • Foci of punctate or gyriform T1 shortening


      • T2 hyperintensity typically much larger


      • Basal ganglia, cortex most common sites


Helpful Clues for Rare Diagnoses

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Aug 7, 2016 | Posted by in NEUROLOGY | Comments Off on T1/T2 Hyperintense Parenchymal Lesions

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