Abnormalities of Consciousness

Question 1

“Brain-dead”

Answer 1

Comatose + compromised brainstem reflexes & vital functions that require life support

Question 2

What tract is responsible for consciousness?

Answer 2

ARAS (Ascending Reticular Activating System)

Question 3

What etiologies cause altered consciousness

Answer 3

1. Bilateral/diffuse cerebrocortical disease (traumatic cerebral edema, toxins)
2. Damage to the RAS (compression, damage to parenchyma)

Question 4

Normal ICP should be what?

Answer 4

less than 10mg of mercury (Hg)

Question 5

What is the Monroe-Kellie Hypothesis?

Answer 5

IF ICP increases, body compensates by either first, decreasing CSF volume, and then once this response gets overwhelmed, decreasing cerebral blood flow (latter is BAD after certain point!)

Question 6

What is Intracranial Hypertension (ICH), and the cycle of ICH & ICP?

Answer 6

Elevated ICP // beyond point where physiological function is normal -> -> because ICP is so high, body tries to compensate by decreased cerebral blood flow -> hypotension -> increase CSF & cerebral blood flow -> ICH —> VISCIOUS CYCLE!!

Question 7

What are detrimental effects of DECREASED CBF?

Answer 7

Decreased cerebral perfusion -> hypoxia, ischemia (affects neurons first! then glial cells, then endothelial cells)

Question 8

Cranial nerve deficits related to midbrain compression?

Answer 8

Occipital lobe of cerebrum blood edema-> increased pressure on midbrain (CN III & CN IV)

Question 9

Caudal Transtentorial Herniation (caused by ICP) increases pressure on what part of the brain?

Answer 9

Midbrain

Question 10

Rostral Transtentorial Herniation (caused by ICP) increases pressure on what part of the brain?

Answer 10

Midbrain & Cerebellum

Question 11

Foramen Magnum Herniation (caused by ICP) increases pressure on what part of the brain?

Answer 11

Acute herniation of the midbrain!

Question 12

Subfalcine Herniation - what is it?

Answer 12

Separated cerebrum down midline -> decreased consciousness, hemiparesis, coma

Question 13

Transcalvarium Herniation - what is it + causes

Answer 13

Through defect in skull
-trauma
-iatrogenic (open skull to expose tumor during sx)

Question 14

What dictates a detrimental ICP?

Answer 14

The RATE of change! (absolute value unknown).

Question 15

Answer 15

Right forebrain lesion (head tilt ipsilateral to lesion)

Question 16

Answer 16

Right forebrain lesion (head tilt ipsilateral to lesion) with left thoracic proprioceptive defecits

Question 17

What type of herniation?

Answer 17

ROSTRAL transtentorial herniation! - Decerebellate posture

Trunk is twisted and flexed!

Question 18

What type of herniation?

Answer 18

CAUDAL transtentorial herniation
- Decerebrate posture (trunk is NOT twisted or flexed!)

Question 19

Small Animal Coma Scale (Lower # = worse clinical presentation). How does this dictate prognosis?

Answer 19

Do not base prognosis on single coma scale. Instead, should be based on trends / serial evaluations!

Question 20

Traumatic Brain Injury - 1º vs 2º ?

Answer 20

1º = tissue deformation occurs instantaneously to moment of injury, direct damage to parenchyma

2º = initiated by 1º -> self-perpetuating series of events (inflammation, ischemia, free-radical production)

BOTH LEAD TO ICH!!!

Question 21

When not do to cross-sectional imaging of TBI?

Answer 21

If pt has gunshot injury (metal in head interferes with CT /MRI magnet)

Question 22

TBI with coma scale of 8 prognosis

Answer 22

50% chance of mortality; higher than 8 increases prognosis vitality

Question 23

What increases post-traumatic epilepsy development?

Answer 23

The severity of the traumatic brain injury

Question 24

Management of ICH:
Goal 1
Goal 2
Goal 3

Answer 24

Goal 1: Restoration of vital parameters!
Goal 2: Reduce ICP (head elevation, induction of hypothermia [reduce cerebral metabolic rate], avoid jugular compression) ; REFERRAL FOR PHYSICAL INTERVENTIONS
Goal 3: Systemic Supportive Care (analgesic, nursing care, physical therapy)

Question 25

Drugs to decrease ICP? Precautions?

Answer 25

Diuretics (Mannitol, Furosemide)

Mannitol draws intracellular water out of brain and into bloodstream
- ENSURE VITAL PARAMETERS ARE HEALED/ STORED BEFORE ADMIN!

Question 26

Downsides to using barbiturates and NMDA antagonists for ICH pts

Answer 26

hypoventilation, hypotension -> puts pt into pharmacologic-induced coma

Question 27

Describe osmolality & Mannitol’s rheological effects

Answer 27

Higher osmolality = lower water concentration, higher solute concentration (e.g., dehydration)

Lower osmolality = higher water concentration, lower solute concentration (e.g., edema)

Fluid flows from areas of LOW osmolality to HIGH osmolality

MANNITOL INCREASES OSMOLALITY of bloodstream -> BLOODSTREAM OSMOLALITY IS HIGHER THAN TISSUE OSMOLALITY –> Fluid from tissue (BRAIN, CSF) flows OUT INTO to the bloodstream