What are the two potential causes of coma?
Coma may result from diffuse dysfunction of cerebral hemispheres or from damage to reticular activating system in brain stem (especially midbrain).
What are the causes of diffuse cerebral cortical suppression?
This may be due to direct cerebral effects of:
- sedative drugs
- systemic electrolyte disturbances
- various severe metabolic upsets
- ->In these cases of toxic or metabolic encephalopathy, brainstem function is usually preserved until last - may see Cheyne-Stokes respirations.
- trauma, diffuse ischemic damage,may be observed in the period after seizure (postictal).
What are key physical exam findings in patients with coma?
The vestibuloocular reflexes (oculocephalic testing or caloric testing) is critical to this assessment. Pupillary reactions may also be important
What is transtentorial herniation?
Transtentorial herniation occurs with lateralized, supratentorial masses with displacement of the brain away from the expanding lesion.
–>This produces stupor and coma by damaging the midbrain and reticular activating system.
–>The uncus of the temporal lobe is usually the structure that herniates.
What are common symptoms of transtentorial herniation?
- The third cranial nerve is often involved early in transtentorial herniation (with pupillary constrictor fibers usually damaged first).
- ->This is usually ipsilateral to the side of expanding lesion.
- The corticospinal tract is often involved next with contralateral weakness.
- Occasionally, with large shifts of the brain stem, this may be reversed (false localizing sign: Kernohan’s notch).
What physical findings would indicate that coma was due to diffuse cerebral cortical dysfunction rather that to brain stem damage?
With diffuse cerebral cortical dysfunction you would expect to find normal dysinhibited oculovestibulor reflex eye movement to caloric testing. Motor findings and responses would be the same on both sides of the body (symmetrical). It is critical to be sure that there is no structural damage to the reticular formation. This is accomplished by determining whether eye movements are affected (extraocular nuclei are close to reticular formation).
What is the “locked-in” syndrome?
“Locked-in” refers to damage to the base of the pons with preservation of consciousness and vertical eye movements, but loss of all other voluntary movements.
How can you recognize “locked-in” syndrome?
In the “locked-in” syndrome, vertical gaze and convergence is usually preserved.
Eye opening may be preserved (eye closure is passive only). Other voluntary motions (including horizontal gaze included) are abolished.
What is stupor?
Stupor is a nonsleep depression of consciousness where normal reactions to the environment are blunted.
What is coma?
Coma is a nonsleep loss of consciousness where normal reactions to the environment are lost.
What is delirium?
Delerium is a nonsleep depression of consciousness where normal reactions to the environment are blunted and replaced by agitated responses.
What is encephalopathy?
Encephalopathy is diffuse suppression of normal cerebral cortical function that often results in stupor or coma.
What is the reticular activating system?
The reticular activating system is the reticular system connecting the rostral pontine and midbrain through the thalamus to the cerebral cortex
What is decorticate posture?
Decorticate posture is a posture in which the lower limbs are extended and the upper limbs flexed in response to noxious stimuli.
What is decerebrate posture?
Decerebrate posture is a posture in which the lower and upper limbs are extended in response to noxious stimuli.
What is Cheyne-Stokes respiration?
Cheyne-Stokes respiration is a pattern of breathing characterized by waxing and waning amplitude of respiration with preserved respriatory frequency.
