84. Brain States + Coma

Question 1

Attention
Arousal
Cognition
(define)

Answer 1

Attention: maintaining cognitive focus on single task/behavior
Arousal: level of conscious brain activity
Cognition: process of receiving, interpreting + acting on sensory input to the brain

Question 2

How is the brain considered a semi-parallel system?

Answer 2

1. Semi-independent parallel brain fx - domains are distinct, localized with non-essential interaction between domains; yet, association areas coordinate fx requiring coordination between domains
2. Superimposed system for modulating brain activity - basic Glu/GABA signaling modulated by ACh/DA/5HT/NE and focal melatonin/histamine/orexin

Question 3

What is the difference between focal and global brain dysfunction? Signs of global brain dysfunction?

Answer 3

Focal: injuries to specific parts of pathway related to specific neuro fx, showing patterns that localize to specific place in CNS

Global: cannot be localized (Drunk man syndrome bc alcohol is nonfocal insult: ataxia, dysarthria, inattention, confusion, headache)

Question 4

What is the Ascending Reticular Activating System (ARAS)? What NTs does it use and what is the signal path?

What are the 3 patterns of injury that impair arousal?

Answer 4

ARAS: activates brain networks, small nuclei in brainstem to induce arousal, uses ACh and NE

midbrain -> interlaminar nucleus of thalami -> cortex

1. Injury to ARAS in midbrain
2. Injury to BOTH thalami (interrupts transmission of ARAS to cortex)
3. Widespread dysfx of BOTH cerebral hemispheres

Question 5

Define the following:
Coma
Stupor
Obtundation
Delirium
Locked-In
Vegetative
Minimally Conscious

Answer 5

Coma - unresponsiveness and no awareness, no pt response, no evidence of eye opening/circadian rhythm
Stupor - vague state b/w alert + coma; pt can respond but needs constant stim
Obtundation - vague term, milder arousal reduction than stupor

Delirium - fluctuating attention/cognitive clarity with sensory misperceptions/hallucinations; due to generalized illness; assoc with worse prognosis and risk of death

Locked-in: injury to PONS - loss of muscle fx (often CN3 only thing intact - communicate with eye movement); pt conscious but unable to respond with muscle movement
Vegetative: coma but circadian rhythm returns, no awareness, eye opening/movements/autonomic changes (pt transitions from coma to vegetative in 10-30days)

Minimally Conscious: minimal but definite behavioral evidence of self/enviro

Question 6

Define:
Abulia
Akinetic Mutism
Encephalopathy

Answer 6

Abulia: apathetic state with psychomotor retardation but intact cognitive fx (medial frontal lobe injuries)

Akinetic Mutism: extreme abulia (no movement), due to bilateral basal-medial frontal lobe injuries

Encephalopathy: any brain dysfx - generally applied to acute global brain dysfx

Question 7

What are true types of altered mental state (3)?

Answer 7

1. Bihemispheric brain dysfx - anoxic brain injury, intoxications, generalized seizures
2. Bilateral Thalamic dysfx - rare strokes, viral infections, autoimmune dz
3. Midbrain Injury (ARAS) - transtentorial brain herniation, strokes, viral infections, tumors, autoimmune

Question 8

Basic Criteria of Brain Death

Do neurologists need consent to evaluate for brain death? What do we do when loved ones object to life-sustaining tech withdrawal?

Answer 8

1. no purposeful response to stim
2. no brainstem reflexes
3. no spontaneous resp movement
4. clear etiology causing massive brain injury (no reversibility)
5. no other confounding factors

AAN recommends NO consent for brain death eval and that it IS ACCEPTABLE for unilateral withdrawal over loved ones objections