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Brain Herniation Syndromes

Topic updated on 09/04/17 9:11am

Snapshot
  • A 70-year-old man presents to the emergency department with confusion after having a convulsive episode. Prior to having a seizure, the patient reported to having a progressively worsening headache that awoke him from sleep, and right-sided weakness over the course of 7 months. On physical exam, there is weakness 2/5 strength throughout the right-side, and a left pupil that is unresponsive to light. A computerized tomography (CT) scan of the head shows a ring-enhancing lesion with surrounding cerebral edema. (Uncal herniation)
Introduction
  • Clinical definition
    • brain tissue herniation that can result in compression of 
      • brain tissue
      • vascular supply
  • Pathogenesis
    • space occupying masses can result in mass effect (intracranial structure displacement) and they include
      • tumor
      • edema
      • hemorrhage
Herniation Syndromes
 
Three Clinically Important Brain Herniation Syndromes
Herniation Syndrome
Mechanism
Clinical Findings
Transtentorial herniation
  • The medial temporal lobe (especially, the uncus) herniates
    • through the tentorial notch
  • Uncal herniation triad
    • ipsilateral unresponsive ("blown") pupil
    • hemiplegia
      • typically contralateral; however,
        • if midbrain is compressed on the opposite side it can result in
          • ipsilateral hemiplegia (Kernohan's phenomenon)
    • decreased level of consciousness secondary to
      • compression of the midbrain reticular formation and can progress to
        • coma
Central herniation
  • The brainstem becomes downwardly and centrally dispaced
  • Unilateral or bilateral lacteral rectus palsy in cases of
    • mild central herniation that compresses the
      • abducens nerve
  • Bilateral uncal herniation in cases of
    • significant central herniation
  • Tonsillar herniation
    • cerebellar tonsils herniates through the foramen magnum that can result in
      • compression of the midbrain that leads to
        • respiratory arrest
        • cardiovascular instability
        • death
Subfalcine herniation
  • The cingulate gyrus (as well as other structures) herniates under the falx cerebri 
  • At times this can lead to anterior cerebral artery compression under the falx cerebri resulting in
    • infarction
 

 



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