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)
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)
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
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
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
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
7
Q
Signs of Metabolic Coma
A
- Signs - pupils, eye movements and motor responses intact; not focal; random
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