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Nervous System Disorders

Incidence: 14–37% of all intracranial tumors

Metastatic primary:

Six tumors account for 95% of all brain metastases:

  1. Bronchial carcinoma (47%): rarely squamous cell ca.
  2. Breast carcinoma (17%)
  3. GI-tract tumors (15%): colon, rectum
  4. Hypernephroma (10%)
  5. Melanoma (8%)
  6. Choriocarcinoma

In childhood:

  1. Leukemia / lymphoma
  2. Neuroblastoma

◊Brain metastases from sarcomas are exceptionally rare!

Location:

  1. corticomedullary junction of brain (most characteristic)
  2. subarachnoid space = carcinomatous meningitis
  3. subependymal spread (frequent in breast carcinoma)
  4. skull (5%)

N.B.: CORTICAL METASTASES

Presentation:

CT:

MR (combination of T2WI + contrast-enhanced T1WI offer greatest sensitivity):

DDx: glioma (indistinct border, less well defined, lesser amount of vasogenic edema); multifocal inflammatory lesions

Carcinomatous Meningitis (8–15%)!!navigator!!

= Meningeal Carcinomatosis

= metastatic involvement of leptomeninges

Source:

  1. Primary CNS tumor: medulloblastoma, glioblastoma, pineal tumors
  2. Secondary tumor: carcinoma of breast + lung, melanoma, NHL, leukemia

Histo: adenocarcinoma (75%)

Spread:

  1. hematogenous dissemination (most common)
  2. contiguous perineural spread
  3. lymphatic spread
  4. shedding of tumor cells from parenchymal metastases

Associated with: concurrent brain parenchymal metastases (in 20%)

  • Simultaneous occurrence of symptoms localized to more than one area!
  • headaches (50%), seizures (15%), cauda equina syndrome
  • cranial nerve deficits (40%): visual disturbances, diplopia, hearing loss, facial numbness
  • mental status changes: lethargy + confusion (20%)
  • progressive asymmetric weakness of extremities

Dx: harvest of malignant cells ← lumbar puncture positive in 45–55% (1st puncture), 80% (after several taps)

N.B.: Perform MRI prior to lumbar puncture

  • Lumbar puncture contraindicated if intracranial pressure increased!

Location: basal cisterns, lumbar spine (areas of CSF stasis)

  • communicating hydrocephalus ← tumor interferes with CSF reabsorption in pacchionian granulations near vertex
  • ischemic changes ← vasculitis (rare)

CEMR (abnormalities in up to ⅔):

  • linear / nodular enhancement of sulci, cisternal spaces, ventricles with associated effacement
  • diffuse / asymmetric nodular enhancement
  • hydrocephalus
  • cranial nerve enhancement

Patterns:

  1. Dural Meningeal Carcinomatosis
    • rarely associated with positive cytology
    • short discontinuous thin sections of enhancement localized / diffuse curvilinear underneath inner table in expected position of dura
  2. Leptomeningeal Carcinomatosis
    • frequently associated with positive cytology
    • thin rim of subarachnoid enhancement following convolutions of gyri “coating the surface of the brain”
    • discrete leptomeningeal nodules
    • invasion of underlying brain → mass effect + edema

DDx: bacterial / fungal meningitis, postoperative changes (fibrosis), previous subarachnoid hemorrhage, idiopathic cranial pachymeningitis, vasculitis, extramedullary hematopoiesis, primary leptomeningeal gliomatosis, amyloidosis, glioneural heterotopia, Castleman disease, Gaucher disease

Dural Metastasis!!navigator!!

Origin:most common: breast, lung, prostate others: melanoma, lymphoma, RCC, gastric cancer

  • often solitary linear dural thickening / nodular lesion: focal / diffuse involvement
  • ± dural tail
  • avid enhancement ← lack of blood-brain barrier:
    • dural enhancement adjacent to osseous involvement ← dural invasion / reactive dural response
  • The lower the T2 signal the more hypercellular the lesion!

Dural metastases are frequently solitary, potentially leading to a misdiagnosis of meningioma and delay in care.

Hemorrhagic Metastases to Brain (in 3–4%)!!navigator!!

  1. Malignant melanoma
  2. Breast cancer
  3. Choriocarcinoma
  4. Oat cell carcinoma of lung
  5. Renal cell carcinoma
  6. Thyroid carcinoma
  • hyperdense without contrast
  • hypervascular with contrast

mnemonic: MR CT BB

  • Melanoma
  • Renal cell carcinoma
  • Choriocarcinoma
  • Thyroid carcinoma
  • Bronchogenic carcinoma
  • Breast carcinoma

Cystic Metastasis to Brain!!navigator!!

  1. Squamous cell carcinoma of lung
  2. Adenocarcinoma of lung

DDx: benign cyst, abscess

Calcified Metastasis to Brain!!navigator!!

  1. Mucin-producing neoplasm: GI, breast
  2. Cartilage- / bone-forming sarcoma
  3. Effective radio- and chemotherapy

Malignant Melanoma Metastatic to Brain!!navigator!!

Prevalence: 39% at autopsy

Location: cerebrum >cerebellum; usually multiple lesions

  • variable degree of pigmentation
  • tendency for hemorrhage
  1. Melanotic pattern (in 24–54%)
    • paramagnetic property of melanin → T1-shortening effect:
      • hyperintense relative to cortex on T1WI
      • iso- / hypointense relative to cortex on T2WI

    Cause: free radicals in melanin + blood products
    • NO clear consensus on contribution of paramagnetic effect of blood products versus melanin!
  2. Amelanotic pattern (38%)
    • Pattern similar to other brain neoplasm
    • hypo- / isointense on T1WI
    • hyper- / isointense on T2WI
  3. Other patterns
    • isointense on T1WI
    • hyperintense on T2WI

Prognosis: median survival of 113 days after discovery

DDx: primary malignant melanoma of CNS (1% of all melanoma cases; solitary lesion; leptomeningeal / choroid plexus location)

Outline