Depression of consciousness Flashcards
Define stupor.
Stupor is a nonsleep depression of consciousness where normal reactions to the environment are blunted.
Define coma.
Coma is a nonsleep loss of consciousness where normal reactions to the environment are lost.
Define delirium.
Delirium is a nonsleep depression of consciousness where normal reactions to the environment are blunted and replaced by agitated responses.
Define encephalopathy.
Encephalopathy is diffuse suppression of normal cerebral cortical function that often results in stupor or coma.
Define reticular activating system.
The reticular activating system is the reticular system connecting the rostral pontine and midbrain through the thalamus to the cerebral cortex.
Define decorticate posture.
Decorticate posture is a posture in which the lower limbs are extended and the upper limbs flexed in response to noxious stimuli.
Define decerebrate posture.
Decerebrate posture is a posture in which the lower and upper limbs are extended in response to noxious stimuli.
What does a “locked-in” patient present with?
“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.
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.
What type of lesion results in central neurogenic hyperventilation?
Central neurogenic hyperventilation typically occurs with pontine lesions, with increased depth of respiration.
What is ataxic respiration?
Ataxic respiration is a pattern of respiration with irregular depth and frequency of respirations with pauses.
What is the vestibular-ocular reflex and how can it be elicited?
The vestibulo-ocular reflex is the reflex that keeps eyes directed on a target during head movements. It can be elicited by head movments or caloric tests.
What do diencephalic pupils refer to?
Diencephalic pupils refer to bilaterally small pupils with lesions of the thalamus.
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?
- Sedative drugs
- Systemic electrolyte disturbances
- Various severe metabolic upsets
- Trauma
- Diffuse ischemic damage
- May be observed in the period after seizure (postictal).
In toxic or metabolic encephalopathy, brainstem function is usually preserved until last - may see Cheyne-Stokes respirations.
What physical findings would indicate that coma was due to diffuse cerebral cortical dysfunction rather that to brain stem damage?
- Diffuse cerebral cortical dysfunction
- Normal VOR with caloric testing.
- Motor findings and responses are symmetrical.
- It is critical to be sure that there is no structural damage to the reticular formation.
- Determinie whether eye movements are affected (extraocular nuclei are close to reticular formation).
What are key physical exam findings in patients with coma?
- Test VOR and pupillary reactions
What is transtentorial herniation?
Transtentorial herniation occurs with lateralized, supratentorial masses with displacement of the brain away from the expanding lesion.
- 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?
- CN III involvement => pupillary constrictor fiber damage
- Usually ipsilateral to the side of expanding lesion.
- Corticospinal tract involvement with contralateral weakness.
- Occasionally, with large shifts of the brain stem, this may be reversed (false localizing sign: Kernohan’s notch).
What is the “locked-in” syndrome?
- Locked-in syndrome usually results from damage at the level of the pons.
- Consciousness is preserved.
How can you recognize “locked-in” syndrome?
In the “locked-in” syndrome:
- Vertical gaze, convergence, and eye opening is preserved.
- Other voluntary motions (i.e. horizontal gaze) are abolished.
