Chapter 24: Hypoxia & Ischemic Brain Injury

Question 1

DEFINITION:

Most typically defined as a complete lack of oxygen in arterial blood, due to a profound and sudden medical event such as cardiac arrest or loss of perfusion pressure

Answer 1

Anoxia

Question 2

DEFINITION:

A deficient amount of oxygen availability in the blood supply to the brain. It is distinguished from anoxia, but the two are often used interchangeably in the literature and medical reports

Answer 2

Hypoxia

Question 3

DEFINITION:

Another term commonly used to refer to reduced partial pressure oxygen in arterial blood (<60 mm Hg).

Answer 3

Hypoxemia

Note: Hypoxemia can lead to hypoxia

Question 4

DEFINITION:

The failure of perfusion of blood through the cerebral vessels to tissue (e.g., lack of blood supply).

Answer 4

Ischemia

Note: Both ischemia and anoxia are usually involved in cases of profound and sudden cardiac arrest

Question 5

What ACUTE conditions may cause hypoxic-ischemic brain damage?

Answer 5

• Cardiac Arrest
• Acute respiratory distress syndrome (ARDS)
• Carbon monoxide poisoning
• Suffocation, drowning, hanging
• Massive blood loss due to trauma
• Prolonged seizures
• Anesthesia accidents in surgical procedures

Question 6

What CHRONIC conditions may cause hypoxic-ischemic brain damage?

Answer 6

• Chronic obstructive pulmonary disease (COPD)
• Obstructive sleep apnea (OSA)
• Asthma
• Conditions that paralyze the respiratory system (e.g.,, amyotrophic lateral sclerosis, myasthenia gravis, etc.)

Question 7

What brain regions show vulnerability to hypoxia/ischemia?

Answer 7

• Neocortex (layers 3, 5, 6)
• Hippocampus (pyramidal cells in CA1)
• Basal ganglia (striatum, globus pallidus)
• Cerebellar regions (Purkinje cells)
• Visual cortex
• Thalamus

Question 8

DEFINITION:

Apoptosis

Answer 8

Programmed cell death.

Apoptosis is part of normal regulation and turnover of cells, but can also result from pathologic processes such as ischemic.

Question 9

DEFINITION:

Adenosine Triphosphate

Answer 9

Adenosine Triphosphate (ATP) is a chemical compound that provides energy for cells/neurons.

Note: under anoxic/hypoxic conditions, less ATP becomes available in the neuron, leading it to catabolize itself.

Question 10

DEFINITION:

Chronic obstructive pulmonary disease (COPD)

Answer 10

A term that encompasses several conditions of pulmonary disease (e.g., emphysema, bronchitis) in which there is progressive obstruction of expiration; COPD can produce chronic hypoxia and, depending on the severity, may result in cognitive impairment.

Question 11

DEFINITION:

Glutamate

Answer 11

The most common excitatory neurotransmitter in the brain. Under conditions of anoxia/hypoxia, excessive amounts of glutamate are released into the synaptic cleft, and it becomes excitotoxic, as well as contributing to further deleterious processes in the neuron.

Question 12

DEFINITION:

Ischemic-hypoxic encephalopathy

Answer 12

Refers to the encephalopathy resulting from the combined effects of anoxia/hypoxia and ischemia. In their purest presentations, anoxia/hypoxia and ischemia may produce somewhat different neuropathology, but most cases in which the brain suffers marked disruption of oxygen supply inolve both processes.

Question 13

DEFINITION:

Necrosis

Answer 13

Refers to the death of tissue or neurons, typically due to insufficient blood supply.

Question 14

DEFINITION:

Obstructive sleep apnea (OSA)

Answer 14

a disorder that involves recurrent episodes of blood oxygen desaturation and also disrupts normal sleep architecture. During episodes of total breathing cessation (apnea) or partial (hypopnea), blood oxygen saturation can fall to harmfully low levels, resulting in repeated hypoxic periods.

Question 15

DEFINITION:

Partial pressure of oxygen (PaO2)

Answer 15

Partial pressure refers to the pressure exerted independently by a specific gas within a larger mix of gases. The partial pressure of arterial oxygen (PaO2) in healthy adults at sea level is typically 95-100 mm Hg. When this level rapidly drops, complex cognitive processes, memory, and judgment show impairment.

Question 16

DEFINITION:

Watershed Region

Answer 16

In the brain, refers to overlapping border zones between the distal supplies of two arteries. For example, the region supplied by the distal branches of the middle and anterior cerebral arteries is a watershed region. Watershed regions are particularly vulnerable to the effects of hypoxia/ischemia.

Question 17

Which of the following regions of the brain would likely be LEAST sensitive to the effects of anoxia/hypoxia?

A) Hippocampus
B) Globus Pallidus
C) Broca’s area
D) cerebellar Purkinje cells

Answer 17

C - Broca’s Area

Brain regions most sensitive to anoxia/hypoxia include those with the highest metabolic demand and those in watershed or distal regions of the cerebral vascular system. Although all brain regions are vulnerable if anoxia/hypoxia is severe, in general, regions with robust vascular supply (e.g., Broca’s area) are less vulnerable).

Question 18

What are the expectations for Neuropsych after Hypoxia/Ischemia:

Intelligence/Achievement

Answer 18

Not typically affected, but overall scores may be reduced due to impairments in processing speed and efficiency

Question 19

What are the expectations for Neuropsych after Hypoxia/Ischemia:

Attention/Concentration

Answer 19

Gross confusion is often present very early in recovery.

Impaired attention and concentration continue to be long-term issues.

Distractability often early and late in the process.

Question 20

What are the expectations for Neuropsych after Hypoxia/Ischemia:

Processing Speed

Answer 20

often impaired both cognitively and motorically

Question 21

What are the expectations for Neuropsych after Hypoxia/Ischemia:

Language

Answer 21

Formal language disorders are rarely seen.

Question 22

What are the expectations for Neuropsych after Hypoxia/Ischemia:

Visuospatial

Answer 22

if watershed zones are affected, deficits can be noticeable.

Lower performance might be related to slow information processing

Question 23

What are the expectations for Neuropsych after Hypoxia/Ischemia:

Memory

Answer 23

Impairments in storage, capacity, and retrieval are common.

Severe cases with bilateral hippocampal damage, a marked amnestic state may be evident.

Question 24

What are the expectations for Neuropsych after Hypoxia/Ischemia:

Executive Functions

Answer 24

Milder cases – minimally affected

Severe – some ppl sustain orbitofrontal damage b/c this is a watershed region.

Question 25

What are the expectations for Neuropsych after Hypoxia/Ischemia: Sensorimotor Functions

Answer 25

Severe -- can lead to spastic quadriparesis, ataxia, parkinsonism syndromes, and other motor impairments Risk -- basal ganglia and cerebellum are at high risk for injury

Question 26

What are the expectations for Neuropsych after Hypoxia/Ischemia: Emotion and Personality

Answer 26

1) Anosagnosia -- impaired self awareness; 2) | Depression; 3) Changes in self-regulation

Question 27

Which of the following would be expected to show the lowest vulnerability to the effects of anoxia/hypoxia? a) areas supplied by the lenticulostriate arteries b) watershed regions between the major arteries c) regions with high metabolic demand d) area of bifurcation of the major branches of the middle cerebral artery

Answer 27

D - area of bifurcation of the major branches of the middle cerebral artery

Question 28

Ischemia is defined as ____. a) a total lack of oxygen in the arterial blood b) failure of perfusion of blood through the cerebral vessels to tissue c) excessive carbon dioxide in the blood d) insufficient expiration through the pulmonary system

Answer 28

B - failure of perfusion of blood through the cerebral vessels to tissue Ischemia results from loss of perfusion of blood supply, in contrast to when there is adequate supply but low or lack of oxygen content (anoxia/hypoxia). In most severe cases, both ischemia and anoxia/hypoxia exist.

Question 29

Under anoxic/hypoxic conditions, when neurons can no longer replenish ATP, the following response occurs: a) neurons begin to self-hibernate so as to minimize metabolic processes b) the brain diverts stored ATP from other brain regions to the hypoxic area c) a series of neurotoxic processes are initiated that lead to neuronal death d) axons rapidly rupture and disintigrate

Answer 29

C - A series of neurotoxic processes are initiated that lead to neuronal death Neurons store virtually no energy and thus loss of O2 and glucose result in rapid ATP depletion. If not rapidly pursued, neuronal death occurs.

Question 30

A complete loss of oxygen in the arterial blood or tissues is referred to as ___. a) hyponatremia b) anoxia c) hypoxemia d) apoptosis

Answer 30

B - Anoxia

Question 31

The pattern of anoxic/hypoxic brain injury in neonates found to be most strongly associated with long-term outcome is injury to which areas? a) basal ganglia and thalamus b) deep brainstem nuclei c) watershed regions d) dorsolateral prefrontal cortex

Answer 31

A - basal ganglia and thalamus The predominant pattern of brain injury in neonates found to be most strongly associated with long-term outcome, more so than the severity of injury in any given region, is injury to the basal ganglia and thalamus.

Question 32

Which of the following cognitive disorders are least likely to be seen following hypoxic/ischemic damage? a) amnestic syndrome b) visuospatial deficits c) impaired processing speed d) impaired attention/working memory

Answer 32

B - visuospatial deficits Impaired memory, processing speed, and attention are common cognitive problems following hypoxia/ischemia. Visuospatial deficits are much less commonly seen.

Question 33

In severe cases of anoxic/hypoxic injury involving basal ganglia and cerebellar structures, you would be least likely to observe ____. a) spastic quadriparesis b) ataxia c) homonymous hemianopsia d) dystonia

Answer 33

C - homonymous hemianopsia Severe hypoxic injury can cause spastic quadriparesis, ataxia, and other motor impairments/dysfunction. A homonymous hemianopsia (visual field defect) would be least likely in this case. Visual impairments may be observed when injury involves watershed zones.

Question 34

of the following areas of functioning, which neuropsychological domain tends to be most resilient to anoxic/hypoxic injury? a) contextual verbal memory b) information processing speed c) visuospatial memory d) intellectual functioning

Answer 34

D - intellectual functioning Hold tests are not typically affected, but overall scores may be reduced due to impairments in processing speed and efficiency.

Question 35

Which of the following is a poor prognostic indicator for functional recovery from an anoxic/hypoxic incident? a) amnesia for the first day of hospitalization b) coma longer than 6 hours c) Glasgow Coma Scale of >12 d) seizure on day of admission

Answer 35

B - coma longer than 6 hours Coma is a poor prognostic indicator. A syncopal episode would suggest a very brief loss of consciousness that would be unlikely, in and of itself, to cause any lasting injury.