Tentorial herniation

The clinical features of tentorial herniation include:

• pupils dilated and unreactive to light:
  • due to compression of the III nerve and oculomotor nucleus
  • the palsy is unilateral at first - on the side of the lesion - but later becomes bilateral
    
    
• ptosis or impaired eye movements:
  • may be difficult to discern if conscious level depressed
  • upward gaze is usually lost first because of pressure on the pretectum and superior colliculi
    
    
• homonympus hemianopia - due to occlusion of posterior cerebral artery
  
  
• limb weakness on same side of lesion:
  • a false localising sign - due to pressure from the edge of the tentorium on the opposite cerebral peduncle - Kernohan's notch
    
    
• diabetes insipidus - from downward action on pituitary stalk and hypothalamus
  
  
• may progress to tonsillar herniation