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IB. Effects of space-occupying lesions

B. Effects of Supratentorial Space-occupying Lesions (SOL)

Displacement effects of rapidly expanding SOL include:

  • Cingulate gyrus herniation under the falx cerebri (subfalcine herniation)
  • Midline shift (lateral displacement)
  • Uncal (transtentorial, uncinate, mesial temporal) herniation - herniation of the medial temporal lobe (uncus) across the tentorium cerebelli
  • Cerebellar tonsil (tonsillar) herniation through the foramen magnum
  • Downward displacement of the diencephalon and brainstem

1. Consequences of cerebellar tonsil herniation
Displacement of the cerebellar tonsils through the foramen magnum compresses the medullary respiratory centers, leading to death.

2. Consequences of lateral displacement of brain
Changing levels of consciousness have been correlated with lateral displacement of diencephalon (containing parts of the ascending reticular activating system.)

This coronal section shows cingulate gyrus herniation and midline shift. Uncal herniation and downward displacement of the brainstem also occurred in this patient.
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