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Extra-axial is a descriptive term to denote lesions that are external to the brain parenchyma, in contrast to intra-axial which describes lesions within the brain substance. 

Often it is trivially easy to distinguish an intra-axial from an extra-axial mass. In many cases, especially when the mass is large and associated with parenchymal changes, such as edema, localization can be more difficult. A number of features are helpful in suggesting that a mass or lesion is extra-axial, including: 

Examples (non-exhaustive) of extra-axial lesions include:

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Article information

rID: 7961
Section: Gamuts
Synonyms or Alternate Spellings:
  • Extraaxial

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Cases and figures

  • Case 1: subarachnoid hemorrhage (SAH)
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  • Case 2: hemangiopericytoma
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  • Case 3: extradural hemorrhage (EDH)
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  • Case 4: arachnoid cyst
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  • Case 5: subdural hemorrhage (SDH)
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  • Case 6: all three types of extra-axial hemorrhage
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