16. Ischemia Pathology (McDonald)

Question 1

What are the four causes of global cerebral ischemia?

Answer 1

Cardiac arrest, HTN, asphyxia, hypoglycemia from insulinoma

Question 2

If there is minor ischemia, what happens?

Answer 2

Transient neurological deficits but no permanent damage

Question 3

In global cerebral ischemia with diffuse cortical injury, what do we see clinically?

Answer 3

Flat EEG, brainstem damage, absent respiratory drive, absent reflexes, absent cerebral perfusion

Question 4

Respirator brain path

Answer 4

Occurs when patient is on a ventilator and in a coma
Repeated cycles of edema and ischemia lead to necrosis
This results in autolysis and softening of the brain

Question 5

What are the common sites of primary thrombosis leading to infarction in focal cerebral ischemia?

Answer 5

Carotid artery bifurcation
MCA
Basilar artery

Question 6

What conditions are associated with focal cerebral ischemia?

Answer 6

HTN, diabetes, atherosclerosis

Question 7

Which cells of the CNS are most susceptible to hypoxia?

Answer 7

Neurons

Question 8

Timeline of ischemic injury

Answer 8

Early stage (24hrs): RED NEURONS (eosinophillic change of neurons) and neutrophil infiltration
Subacute (1day-1wk): Necrosis, macrophage infiltrate, gliosis starts
Repair (+2wks): Gliosis, pseudolaminar necrosis

Question 9

Which cells are commonly damaged by global ischemia and undergo red neuronal change?

Answer 9

Pyramidal cells of hippocampus
Pyramidal cells of cerebral cortex
Purkinje cells of cerebellum

Question 10

Thrombotic strokes

Answer 10

Atherosclerotic plague present ruptures, causing an ischemic event. Can lyse, but because thrombus is due to a ruptured plague, the thrombus reforms. PALE infarct

Question 11

Embolic strokes

Answer 11

Embolus lodges in vessel, leading to ischemic event. Body lyses the embolus, blood flows through area again.
RED or HEMORRHAGIC INFARCT

Question 12

Lacunar strokes

Answer 12

Hyaline narrowing of small vessels (lenticulostriate vessels that penetrate deep into the brain) leads to ischemia –> small infarcts –> liquefactive necrosis –> small, cavities (LACUNAE) form
Lipid-laden macrophages

Question 13

What condition is typically also present in a patient with lacunar strokes?

Answer 13

Hypertension

Question 14

CADASIL (Cerebral AD Arteriopathy with Subcortical Infarcts and Leukoencephalopathy)

Answer 14

Recurrent strokes and dementia
Mutations in NOTCH3
Abnormalities of white matter and concentric narrowing of the adventitia and media

Question 15

What is the main cause of emboli to the brain?

Answer 15

Atrial fibrillation

Question 16

How to Fat emboli, Air emboli, and tumor emboli occur?

Answer 16

Fat: Usually due to broken bones; fat from bone marrow increases fat in the bloodstream –> can cause white matter hemorrhages and DIC
Air: Due to penetrating injury or oral sex on a pregnant female
Tumor: Metastasis

Question 17

Where do emboli usually go?

Answer 17

Area of distribution of Middle Cerebral Artery (MCA). Tend to lodge in bifurcations

Question 18

What is asphyxiation

Answer 18

Can’t acquire enough O2 by breathing

Question 19

Suffocation is a part of asphyxiation. What can cause suffocation?

Answer 19

Environment (inadequate O2 in air), smothering (occlusion of external airway i.e. pillow over face), choking (occlusion of internal air passages), suffocating gases (CO)

Question 20

CO poisoning

Answer 20

Displaces O2, causing the SaO2 to decrease
Skin: Cherry-red appearance
First sign is headache

Question 21

Strangulation

Answer 21

Compression of vessels of the neck

Note: Suffocation was due to occlusion of internal or external airway

Question 22

Hanging is which type of asphyxiation?

Answer 22

strangulation

Question 23

What are the two types of strangulations?

Answer 23

Ligature strangulation: compression of neck structures (rope/tie)
Manual strangulation: compression of neck structures by hands/forearm

Question 24

If the jugular veins are occluded while the carotids are open, how does this manifest clinically?

Answer 24

Petechiae in the eye

Question 25

Chemical asphyxiation is due to which two chemicals? Talk about them

Answer 25

Hydrogen cyanide: cellular hypoxia caused by HCN competing with Fe, inhibiting ETC. Smells like almonds. Used in gas chambers, house fires
Hydrogen sulfide: produced by fermentation of organic matter, rotten egg smell. Sewers and cess pools; rapid death

Question 26

Positional asphyxia

Answer 26

Usually occurs in drug users
Intoxicated patients fall into a position that they cannot get themselves out of
Trapped in positions that impairs breathing –> congestion, cyanosis, petechiae

Question 27

Traumatic asphyxia

Answer 27

Heavy weight compresses the chest or upper abdomen
Congestion and petechiae (compression of heart, blood cannot exit the head and neck –> pinpoint hemorrhages from blood vessels breaking)

Question 28

Overlaying asphyxia

Answer 28

Rolling over small children while they are in bed