Herniation Syndromes

Brain herniation is the displacement of part of the brain into a region that it does not normally occupy. Herniation syndromes include:

• Transcalvarial
  Herniation of some part of the brain through a skull defect.
• Subfalcine
  Displacement of the cingulate gyrus under the falx cerebri.
  • Occurs due to a lateral supratentorial mass
  • May result in “midline shift”
  • May compress ACA, leading to ischaemia and further infarction
• Central tentorial
  Symmetrical caudal displacement of the thalamic regions through the tentorium cerebelli.
• Uncal
  Displacement of the uncinate process of the temporal lobe into the tentorium cerebelli.
• Upward transtentorial
  Cranial displacement of the posterior fossa contents through the tentorium cerebelli.
  • Posterior fossa mass lesions
  • May be precipitated by EVD drainage ↑ supra-tentorial ICP.
• Tonsillar
  Displacement of cerebellar tonsils into the foramen magnum.

Comparison

Features of Herniation Syndromes

Syndrome	Radiological Features	Clinical Features
Transcalvarial	Variable	Variable
Subfalcine	Displacement of the cingulate gyrus under the falx Midline shift Contralateral hydrocephalus	↓ GCS Leg weakness
Central tentorial	Obliteration of basal cisterns ↑ Brainstem diameter	↓ GCS DI Pituitary ischaemia due to stretching of the pituitary stalk. Parinaud’s Syndrome Mid-dilated pupil Failure of upward gaze Conjugate downward gaze
Uncal	Medial displacement of uncus and temporal lobe Effaced midbrain Effacement of suprasellar cistern	↓ GCS Ipsilateral CN III palsy Fixed and dilated pupil. Hemiparesis Cortical blindness Contralateral CN III palsy may occur with ↑ herniation
Upward transtentorial	Hydrocephalus	↓ GCS Miosis Asymmetric Doll’s eye Decerebrate
Tonsillar	Cerebellar tonsils beneath foramen magnum	↓ GCS Apnoea Cushing’s response

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References