Coma Flashcards

1
Q

Anatomy of Coma

A
  • ARAS (esp cholinergic pedunculopontine fibers)—> thalamus —> cortex
  • ARAS excites reticular thalamic nuclei —> inhibit the relay thalamic nuclei (transmission mode)
    - De-synchronized EEG (associated w/ wakefulness)
  • If no ARAS excitation —> no inhibition of relay thalamic neurons (burst mode - not responsive to stimuli)
    - Synchronized EEG (associated w/ lack of wakefulness)
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2
Q

Lethargy v Stupor v Coma

A
  • Lethargy - mild sleep-like state; can wake w/ gentle stimulus
  • Stupor - can be brought to somewhat wakeful state w/ vigorous stimulation
  • Coma - unarousable and unresponsive; cannot induce wakefulness (even if some motor responses may exist)
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3
Q

Types of Respirations & Localization (4)

A
  • Cheyne-Stokes - crescendo-decresendo periods sometimes w/ apnea pauses between; localizes to hemispheres or diencephalon (can be intoxication, metabolic, CHF)
  • Central Neurogenic Hyperventilation - sustained, heavy, rapid hyperventilation; localizes to midbrain
  • Apneustic respirations - inspiratory cramps; localizes to pons always
  • Ataxic respirations - uncoordinated rate and rhythm; RANDOM; localizes to lower pons or medulla
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4
Q

3 Categories of Diseases Causing Coma

A
  • Structural Lesions - visible changes - more focal effects
    • Supra-tentorial - mass lesions, meningitis, encephalitis, ischemic encephalopathy, subdural or epidural hematoma, large hemispheric infarction, brain abscess, neoplasm
    • Sub-tentorial - brainstem, thalamic or cerebellar hemorrhage, infarction or abscess
  • Metabolic - no visible lesion- more widespread (MOST COMMON); Drug/alcohol intoxications, hypoglycemia, hepatic failure, shock, non-convulsive SE, heat stroke, hypoxia
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5
Q

Signs of Supratentorial Lesion

A
  • Signs - Cheyne Stokes breathing; normal eye movements b/c brainstem intact; normal pupils; hemiparesis
  • If brainstem becomes involved LATER… poor reactivity of pupils (EWN), central neurogenic hyperventilation, incomplete eye movements, decerebrate or decorticate rigidity
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6
Q

Signs of Subtentorial Lesion

A
  • Signs - could cause coma, central neurogenic hyperventilation or apneustic respirations, absent eye movements for doll’s head or cold caloric test, abnormal posture or decerebrate rigidity
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7
Q

Signs of Metabolic Coma

A
  • Signs - pupils, eye movements and motor responses intact; not focal; random
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8
Q

Changes in Eye Movements & Pupils in Coma (+ localization)

A
  • Pupils
    • If diencephalon… parasymp fine but no sympathetic —> small pupils but reactive (EWN)
    • CN III lesion - dilated and non-reactive
    • Midbrain lesion - mid-position; poor or non-reactive pupils
    • Pontine lesion - pinpoint pupils (also narcotics)
    • Metabolic disorders - usually pupils are still reactive even if they are small
  • Eye Movements
    • Brainstem lesion —> absent movement to doll’s eyes maneuver and no nystagmus in cold caloric stimulation
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