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Differential Diagnosis of Nervous System Disorders

Pachymeningeal Enhancement!!navigator!!

= DURA-ARACHNOID ENHANCEMENT

Site: periosteum of inner table + meningeal layer

Location: dural reflections of falx cerebri + tentorium cerebelli + cavernous sinus; subcortical

  • inconspicuous enhancement against inner table on CT
  • thin linear discontinuous enhancement on T1WI

Cause:

  1. BENIGN
    1. Transient postoperative enhancement
    2. Intracranial hypotension
    3. Granulomatous disease of basilar meninges (sarcoidosis, tuberculosis, Wegener granulomatosis, luetic gumma, rheumatoid nodules, fungal disease)
    4. Uncomplicated lumbar puncture (in <5%)
  2. MALIGNANT
    1. Meningioma
    2. Secondary CNS lymphoma
    3. Metastases: breast, prostate, melanoma, RCC

Leptomeningeal Enhancement!!navigator!!

= PIA-ARACHNOID ENHANCEMENT

Site: pial surface of brain

Location: subarachnoid spaces of sulci + cisterns

  • gyriform / serpentine enhancement

Cause:

  1. Infectious meningitis (bacterial, viral, fungal)
  2. Carcinomatous meningitis
    1. primary CNS tumor: medulloblastoma, ependymoma, glioblastoma, oligodendroglioma)
    2. secondary tumor: lymphoma, breast cancer

Gyral Enhancement!!navigator!!

  • serpentine enhancement
  1. VASCULAR
    • abrupt onset of symptoms
    • often in territory of single artery (MCA in 60%)
    1. Reperfusion of ischemic brain
    2. Vasodilative phase of migraine headaches
    3. Posterior reversible encephalopathy syndrome
    4. Vasodilation with seizures
    5. Subarachnoid hemorrhage (enhancing fibroblastic proliferation)
    6. Subacute / acute brain infarct: luxury perfusion
    7. Dural sinus thrombosis: venous congestion
  2. INFLAMMATORY
    • nonspecific headache / lethargy
    • multiple territories
    1. Herpes simplex encephalitis
  3. NEOPLASTIC
    1. Meningeal carcinomatosis from systemic tumor, eg, breast carcinoma, small cell carcinoma of lung, malignant melanoma, lymphoma / leukemia
    2. Seeding primary CNS tumor:
      1. Medulloblastoma
      2. Pineoblastoma
      3. Ependymoma

mnemonic: CAL MICE

  • Cerebritis
  • Arteriovenous malformation
  • Lymphoma
  • Meningitis
  • Infarct
  • Carcinomatosis
  • Encephalitis

Nodular Cortical / Subcortical Enhancement!!navigator!!

Cause: hematogenous dissemination

  1. Metastasis
  2. Clot embolus
  • small <2 cm circumscribed lesions near gray–white matter junction

Small Spherical Ring-enhancing Lesion at Corticomedullary Margin with Substantial Amount of Vasogenic Edema

  1. Primary / secondary neoplasm
  2. Abscess of brain
    1. bacterial / granulomatous: Streptococcus, Staphylococcus, Bacteroides, Mycobacteria, Nocardia, Actinomyces, Listeria
    2. fungal: Zygomycetes, Histoplasma, Coccidioides, Aspergillus, Cryptococcus
    3. parasitic: Toxoplasma, Taenia (cysticercosis), Entamoeba, Echinococcus
  3. Subacute infarction
  4. Resolving hematoma

Deep Ring-enhancing Lesion!!navigator!!

Cause:

  1. Glioma (40%): single lesion in 77%
  2. Metastasis (30%): single lesion in 45%
  3. Abscess (8%): multiple lesions in 75%
  4. Demyelinating disease (6%): multiple lesions in 85%
  5. Necrotic high-grade primary neoplasm (GBM)
    • wavy undulating rim of >10 mm in thickness
  6. Fluid-secreting low-grade primary neoplasm (pilocytic astrocytoma, hemangioblastoma)
    • enhancing mural nodule within cyst

Pathogenesis:

  1. hypervascular margin of lesion = granulation tissue / peripheral vascular channels / hypervascular tumor capsule
  2. breakdown of blood-brain barrier = leakage of contrast out of abnormally permeable vessels into extracellular fluid space
  3. hypodense center = avascular / hypovascular (requires time to fill) / cystic degeneration

Incidence of ring blush:

abscess (in 73%); glioblastoma (in 48%); metastasis (in 33%); grade II astrocytoma (in 26%) [NOT in grade I astrocytoma]

Multiple Ring-enhancing Lesions in Immunocompromised Patient

  1. Lymphoma (necrotic)
    • thick nodular ring enhancement
  2. Metastatic disease
  3. Multiple abscesses
    • restricted diffusion (ADC values lower than lymphoma / metastatic disease / toxoplasmosis)

Solitary Ring-enhancing Lesion of Brain!!navigator!!

  1. NEOPLASM
    1. Primary neoplasm: high-grade glioma, meningioma, lymphoma, leukemia, pituitary macroadenoma, acoustic neuroma, craniopharyngioma
    2. Metastatic carcinoma + sarcoma
    • thick irregular peripheral enhancement
    • more nodular + irregular appearance compared with abscess
  2. INFECTION / INFLAMMATION
    Abscess / granuloma: bacterial, fungal, parasitic
    • thin ring iso- to hypointense relative to white matter using long repetition time
    • thin medial margin → propensity for intraventricular rupture
    • restricted diffusion of necrotic center
  3. HEMORRHAGIC-ISCHEMIC LESION
    1. Resolving infarction
    2. Aging hematoma
    3. Operative bed following resection
    4. Thrombosed aneurysm
  4. DEMYELINATING DISORDER
    1. Radiation necrosis
    2. Tumefactive demyelinating lesion (“singular sclerosis”)
    3. Necrotizing leukoencephalopathy after methotrexate
    • often incomplete ring enhancement with open portion of ring abutting gray matter
    • arc pattern with ongoing plaque activity at one margin = more classic asymmetric comma-shaped peripheral-enhancement pattern compared with abscess

mnemonic: MAGICAL DR

  • Metastasis
  • Abscess / cerebritis
  • Glioblastoma multiforme, Glioma
  • Infarct (resolving), Impact
  • Contusion
  • AIDS toxoplasmosis
  • Lymphoma (often AIDS-related)
  • Demyelinating disease
  • Radiation necrosis, Resolving hematoma

Isolated Ring-enhancing Lesion of Brainstem

  1. NEOPLASM
    1. primary
    2. secondary
  2. Infection / Inflammation
    1. Abscess
    2. Acute disseminated encephalomyelitis (ADEM)
    3. Multiple sclerosis (1st episode)

Periventricular Enhancement!!navigator!!

  1. Primary CNS lymphoma
  2. Primary glial tumor
  3. Infectious ependymitis

Well-defined Superficial Enhancing Mass!!navigator!!

  1. EXTRAAXIAL DURA-BASED TUMOR
    • displacement of underlying cortex
    • adjacent dural thickening
    • reactive bone changes
    • supply by dural arteries
    1. Meningioma
    2. Metastasis (prostate, breast, melanoma, RCC)
    3. Lymphoma
  2. INTRAAXIAL
    1. Glioblastoma multiforme

Dense & Enhancing Lesion!!navigator!!

  1. Aneurysm
  2. Meningioma
  3. CNS lymphoma
  4. Medulloblastoma
  5. Metastasis

Multifocal Enhancing Lesions!!navigator!!

  1. Multiple infarctions
  2. Arteriovenous malformations
  3. Multifocal primary / secondary neoplasms
  4. Multifocal infectious processes
  5. Demyelinating disease: eg, multiple sclerosis

Innumerable Small Enhancing Cerebral Nodules!!navigator!!

  1. METASTASES
  2. PRIMARY CNS LYMPHOMA
  3. DISSEMINATED INFECTION
    1. Cysticercosis
    2. Histoplasmosis
    3. Tuberculosis
  4. INFLAMMATION
    1. Sarcoidosis
    2. Multiple sclerosis
  5. SUBACUTE MULTIFOCAL INFARCTION
    from hypoperfusion, multiple emboli, cerebral vasculitis (SLE), meningitis, cortical vein thrombosis

Outline