T1/T2 Isointense Parenchymal Lesions



T1/T2 Isointense Parenchymal Lesions


Anne G. Osborn, MD, FACR



DIFFERENTIAL DIAGNOSIS


Common



  • Cerebral Ischemia-Infarction, Hyperacute


  • Intracerebral Hematoma (Hyperacute)


  • Capillary Telangiectasia


  • Developmental Venous Anomaly


  • Meningioma


Less Common



  • Metastases, Parenchymal


  • Lymphoma, Primary CNS


Rare but Important



  • Neurosarcoid


  • Heterotopic Gray Matter


  • Tuber Cinereum Hamartoma


  • Tuberous Sclerosis Complex


  • Cerebral Infarction, Subacute


ESSENTIAL INFORMATION


Key Differential Diagnosis Issues



  • Lesions can be isointense with brain parenchyma generally vs. isointense compared to cortex or white matter


  • Most comparisons are to gray matter


  • Very few parenchymal lesions truly isointense to gray matter on both T1/T2WI



    • FLAIR, PD, DWI may be abnormal when T1/T2WI normal or subtle


    • T2* GRE helpful in hyperacute hemorrhage



      • Detects field homogeneities caused by inhomogeneous clot


      • Detects presence of other lesions (e.g., microhemorrhages)


    • T1 C+ scans increase sensitivity for small vascular malformations, neoplasms


  • Lesions that are really, truly isointense to cortex and neither enhance nor restrict are uncommon



    • Heterotopic gray matter


    • Tuber cinereum hamartoma


Helpful Clues for Common Diagnoses



  • Cerebral Ischemia-Infarction, Hyperacute



    • T1/T2WI typically normal in hyperacute



      • Look for show subtle signs of gyral swelling, sulcal effacement


    • FLAIR



      • Subtle abnormalities may be apparent using narrow windows


      • Look for “dot sign” (intravascular high signal intensity caused by occlusion/slow flow)


      • Found in 10% of patients with acute stroke


  • Intracerebral Hematoma (Hyperacute)



    • Clot contains intracellular oxyhemoglobin, which is diamagnetic


    • Although hyperacute clot can be isointense on T1WI, most hematomas are inhomogeneous, often hyperintense on T2WI


  • Capillary Telangiectasia



    • Can be anywhere



      • Pons, medulla > supratentorial cortex, white matter


    • Imaging



      • Unless unusually large, typically invisible on T1/T2WI


      • Use T2* sequence (become hypointense on GRE, SWI)


      • T1 C+ shows “brush-like” enhancement


      • May see tiny central draining vein within lesion


  • Developmental Venous Anomaly



    • Most common cerebrovascular anomaly


    • Imaging



      • If small, often invisible on T1/T2WI


      • Larger DVAs may have discernible flow void or flow-related enhancement


      • If slow flow in “Medusa head” (medullary veins), may become hypointense on T2* (GRE/SWI)


      • Best seen on T1 C+


  • Meningioma



    • Not truly a parenchymal lesion although some may invaginate into brain


    • Included because often isointense to cortex, difficult to detect on nonenhanced T1WI, T2WI


    • Look for signs of extra-axial location



      • Gray-white matter “buckling”


      • CSF-vascular “cleft”


    • Most enhance on T1 C+


Helpful Clues for Less Common Diagnoses



  • Metastases, Parenchymal



    • Most hyperintense on FLAIR, T2WI


    • Gray-white matter junction distortion



      • Few are isointense on both T1/T2WI


      • Most (not all) have detectable edema



      • Look for subtle alteration in gyral shape, sulcal effacement


    • Most enhance


  • Lymphoma, Primary CNS



    • Hypercellular tumor, high nuclear: cytoplasm ratio



      • Isointense (cortex, basal ganglia) on both T1/T2WI


      • Hemorrhage, necrosis rare unless HIV/AIDS


    • Look for anatomic distortion of deep periventricular structures


    • Almost always enhances


Helpful Clues for Rare Diagnoses

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

Full access? Get Clinical Tree
Get Clinical Tree app for offline access