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RINGS „N THINGS: Imaging Patterns in Differential Diagnosis Anne G. Osborn, M.D. ExpDDxs: Intra-axial (Parenchymal) Lesions • Ring-enhancing lesions, solitary • Ring-enhancing lesion crossing corpus callosum • Ring-enhancing lesions, multiple • Ring-enhancing cyst with nodule 1 1 Smirniotopoulos JG et al: Patterns of contrast enhancement in the brain and meninges. Radiographics 27: 525-51, 2007 SOLITARY RING ENHANCING LESION: Does “M.A.G.I.C.A.L. DR.” Really Work? • Mnemonic 1 • • • • • • • • • 1 Metastasis Abscess/cerebritis Glioblastoma Infarct (resolving), Impact Contusion AIDS toxoplasmosis Lymphoma (AIDS-related) Demyelinating Disease Radiation necrosis, Resolving hematoma Dahnert W: Radiology Review Manual, 5th edition, p. 235. LWW (2003) Well, Not really….. • Common • Metastasis • Abscess • GBM • Less common • Hematoma (subacute) • Infarct (subacute) • Tumefactive demyelination • NCC • Lymphoma • TB • Radiation necrosis • Less common (contd) • Aneurysm (thrombosed) • AVM (thrombosed) • Rare but important • Lacunar infarct (subacute) • Fungal diseases • Parasites RING-ENHANCING LESION: The “Big Three” • Neoplasm • Metastasis • GBM • Infection • Abscess • TB • Parasite • Demyelinating disease • M.S. • ADEM METASTASIS • Gray-white junction • Solid, ring, punctate • Multiple > single ABSCESS • Imaging depends on stage • Ring = late cerebritis, early/late capsule • Findings • • • • Rim T2 hypointense Thin, enhancing rim Restricts on DWI MRS: Acetate, lactate, succinate, cytosolic amino acids GLIOBLASTOMA MULTIFORME • 95% • Central necrosis • Thick, irregular rind • Strong, inhomogeneous enhancement • DWI negative (usually) • Hemorrhage common • Beware: Tumor infiltates way beyond MET VS. ABSCESS • Metastasis • Superficial > deep (graywhite) • Multiple > solitary • Usually no restriction DWI • Abscess • Deep (periventricular) • Restricts on DWI • MRS → acetate, lactate amino acids TR2000/TE35 SOLITARY RING: Less Common Etiologies Subacute hematoma Subacute infarct Demyelination Giant thrombosed aneurysm SOLITARY RING: Less Common Etiologies NCC Lymphoma (HIV/AIDS) TB TB SOLITARY RING: Less Common/Rare Etiologies Thrombosed AVM Fungal disease Radiation necrosis Parasites SOLITARY RING: Summary and Helpful Hints • Restricts? Think infection • Hypointense center on T2? TB • HIV+ patient? 70% = lymphoma • “Looks weird”? Think parasites • MRS shows lactate + peaks at 2 and 0.9 ppm? Think abscess • Older patient with thick, irregular ring? GBM RING-ENHANCING LESION CROSSING CORPUS CALLOSUM • Common • Glioblastoma multiforme • Lymphoma • Less common • “Tumefactive” demyelinating disease GLIOBLASTOMA MULTIFORME • Crosses CC in “butterfly” pattern • Central necrosis → heterogeneous ring enhancement • Hemorrhage common • DDx: Lymphoma (especially HIV/AIDS) LYMPHOMA • Often periventricular • Basal ganglia • Corpus callosum • Ventricular ependyma • Very cellular • Hyperdense on NECT • Isointense to GM on MR (T2 hypointense) • Enhancement • Usually homogeneous • Can be ring-like in HIV/AIDS “TUMEFACTIVE” DEMYELINATING DISEASE • MS > ADEM • White matter mass mimics neoplasm • BUT • Incomplete ring or “horseshoe” enhancement • Open towards cortex MULTIPLE RINGENHANCING LESIONS • Common • • • • Metastases Abscesses/septic emboli Demyelinating disease Neurocysticercosis • Less common • TB • Opportunistic infection (HIV/AIDS) • Lymphoma • GBM (multifocal) • Less common • Resolving hemorrhages • Resolving embolic infarcts • Rare but important • Fungal disease • Parasites • Lyme disease (? demyelination) METASTASES • Multiple ringenhancing lesions • Tend to be at graywhite junction • Variable edema, hemorrhage • No restriction on DWI (usually….) Breast mets Lung mets MULTIPLE ABSCESSES: Septic Emboli • Punctate, complete or incomplete rings • Gray-white junction • Often appear to “encase” sulcus • Restrict on DWI MULTIPLE ABSCESSES: Septic Emboli DEMYELINATING DISEASE • MS, ADEM cause multifocal ring-enhancing lesions • Usually incomplete • May show diffusion restriction along periphery NEUROCYSTICERCOSIS • Common disease • Ring enhancement in colloidal vesicular, granular nodular stages • Multiple enhancing rings uncommon • Most are around cysts trapped in depths of sulci • Parenchymal lesions less common LESS COMMON CAUSES OF MULTIPLE RINGS: Tuberculosis Clue to dx = profound hypointensity on T2WI, FLAIR OTHER LESS COMMON, RARE RINGS HIV/AIDS (toxo) Nocardia Parasites Subacute infarcts (laminar necrosis or embolic) RING-ENHANCING CYSTIC LESION WITH NODULE • Common • • • • (Neurocysticercosis) Pilocytic astrocytoma Ganglioglioma Hemangioblastoma • Less common • • • • • Metastases GBM Abscess Toxoplasmosis Parasites • Rare but important • Pleomorphic xanthoastrocytoma • Lymphoma (HIV/AIDS) • Schwannoma (intraparenchymal) PARENCYHMAL NEOPLASMS THAT COMMONLY HAVE ENHANCING RING + NODULE PXA Ganglioglioma Pilocytic astro Hemangioblastoma LESS COMMON NEOPLASMS Metastasis Schwannoma Lymphoma (HIV/AIDS) GBM NONNEOPLASTIC ENHANCING RING + NODULE Toxoplasmosis (HIV/AIDS) AVM (thrombosed) Parasites (amebic) Tuberculoma RING-ENHANCING CYST + NODULE: Diagnostic Hints • Age • Child? • Posterior fossa: Pilocytic astrocytoma • Hemisphere: Ganglioglioma • Adult? • Posterior fossa?? Met, met, met—then hemangioblastoma! • Hemisphere: Metastasis, GBM • HIV/AIDS? Toxoplasmosis, lymphoma • Patient from endemic area? • Neurocysticercosis (sulci > parenchyma) • Parasites • TB • Dural involvement? PXA!
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