Depression of consciousness

Question 1

Define stupor.

Answer 1

Stupor is a nonsleep depression of consciousness where normal reactions to the environment are blunted.

Question 2

Define coma.

Answer 2

Coma is a nonsleep loss of consciousness where normal reactions to the environment are lost.

Question 3

Define delirium.

Answer 3

Delirium is a nonsleep depression of consciousness where normal reactions to the environment are blunted and replaced by agitated responses.

Question 4

Define encephalopathy.

Answer 4

Encephalopathy is diffuse suppression of normal cerebral cortical function that often results in stupor or coma.

Question 5

Define reticular activating system.

Answer 5

The reticular activating system is the reticular system connecting the rostral pontine and midbrain through the thalamus to the cerebral cortex.

Question 6

Define decorticate posture.

Answer 6

Decorticate posture is a posture in which the lower limbs are extended and the upper limbs flexed in response to noxious stimuli.

Question 7

Define decerebrate posture.

Answer 7

Decerebrate posture is a posture in which the lower and upper limbs are extended in response to noxious stimuli.

Question 8

What does a “locked-in” patient present with?

Answer 8

“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.

Question 9

What is Cheyne-Stokes respiration?

Answer 9

Cheyne-Stokes respiration is a pattern of breathing characterized by waxing and waning amplitude of respiration with preserved respriatory frequency.

Question 10

What type of lesion results in central neurogenic hyperventilation?

Answer 10

Central neurogenic hyperventilation typically occurs with pontine lesions, with increased depth of respiration.

Question 11

What is ataxic respiration?

Answer 11

Ataxic respiration is a pattern of respiration with irregular depth and frequency of respirations with pauses.

Question 12

What is the vestibular-ocular reflex and how can it be elicited?

Answer 12

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.

Question 13

What do diencephalic pupils refer to?

Answer 13

Diencephalic pupils refer to bilaterally small pupils with lesions of the thalamus.

Question 14

What are the two potential causes of coma?

Answer 14

Coma may result from diffuse dysfunction of cerebral hemispheres or from damage to reticular activating system in brain stem (especially midbrain).

Question 15

What are the causes of diffuse cerebral cortical suppression?

Answer 15

• 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.

Question 16

What physical findings would indicate that coma was due to diffuse cerebral cortical dysfunction rather that to brain stem damage?

Answer 16

• 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).

Question 17

What are key physical exam findings in patients with coma?

Answer 17

• Test VOR and pupillary reactions

Question 18

What is transtentorial herniation?

Answer 18

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.

Question 19

What are common symptoms of transtentorial herniation?

Answer 19

• 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).

Question 20

What is the “locked-in” syndrome?

Answer 20

• Locked-in syndrome usually results from damage at the level of the pons.
• Consciousness is preserved.

Question 21

How can you recognize “locked-in” syndrome?

Answer 21

In the “locked-in” syndrome:

• Vertical gaze, convergence, and eye opening is preserved.
• Other voluntary motions (i.e. horizontal gaze) are abolished.