Tonsillar herniation

Dr Craig Hacking et al.

Tonsillar herniation is a type of cerebral herniation characterised by the inferior descent of the cerebellar tonsils below the foramen magnum.

Pathology

It is a secondary sign of significant intra-cranial mass effect. Any intra-axial or extra-axial lesion (e.g. tumour, haemorrhage, stroke, abscess) exerting mass effect on the brain parenchyma can displace the posterior cranial fossa structures inferiorly. In doing so the brainstem is compressed against the clivus thereby altering the vital life-sustaining functions of the pons and medulla, such as the respiratory and cardiac centres.

Non-life threatening tonsillar descent can bee seen in conditions such as Chiari malformations.

Radiographic features

Tonsillar herniation is seen on CT and MRI as effacement of the CSF cisterns surrounding the brainstem and as inferior descent of the cerebellar tonsils below the foramen magnum.

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Article Information

rID: 37113
Section: Gamuts
Synonyms or Alternate Spellings:
  • Tonsillar herniations

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Cases and Figures

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    Case 1: cerebral oedema
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    Case 3: Chiari malformation
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    Case 3: cerebral oedema
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    Herniated cerebel...
    Case 4: acquired tonsillar ectopia
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