17A. Types and etiology of unconsciousness. Coma

Loss of consciousness can only occur if there is injury to the brainstem, injury to both hemispheres, or a metabolic disorder which affects the entire brain. Hungarian literature classifies unconsciousness as either hypnoid or non-hypnoid.

Hypnoid types of decreased consciousness

• Somnolence – patient responds to voice
• Sopor – patient responds to pain
• Coma – patient is completely unresponsive

These can be caused by:

• High intracranial pressure -> Brain herniation
• Intoxication
• Brainstem lesion
• Metabolic cause

Non-hypnoid types of decreased consciousness

• Tenebrosity – decreased awareness after seizure
• Delirium – acute disorientation with agitation, restlessness, etc.
  • Due to alcohol, drugs, meningitis, dehydration, infection, etc.
• Decortication – flexion of upper extremities + extension of lower extremities
  • Due to diffuse brain hypoxia, like cardiac arrest, with subcortical areas intact
• Akinetic mutism – patient is awake but completely unresponsive, no voluntary activity, no communication, no speech
  • Due to frontal lobe lesion
• Locked-in syndrome – patient is awake and aware, but the entire body except the eyelids are paralysed
  • Due to brainstem lesion