Pathology: Edema and Vascular Disorders

Question 1

What cells make up the BBB?

Answer 1

• Pericytes with Endothelial cells form a basement membrane

- Astrocytic foot processes then cover most of the external surface of the vessels

Question 2

What is the response of endothelial cells to hypoxia?

Answer 2

1) short-term exposure causes physiological and reversible modulation of vascular tone and blood flow
2) chronic hypoxic stress results in irreversible remodeling of the vasculature and surrounding tissues, with smooth muscle proliferation and fibrosis

Question 3

What are the potential causes of brain or spinal swelling/ edema? (6)

Answer 3

• Trauma
• Infectious
• Toxins
• Space occupying lesions
• Haemorrhages
• Focal necrosis

Question 4

Why is swelling/ edema so emergent when in the brain or spinal cord?

Answer 4

Due to the confinement of the skull, meninges and vertebral column- leading to increased intracranial or intraspinal pressure

Question 5

When the brain swells, this can lead to herniation of the brain- what are they?

Answer 5

1) Caudal cerebellar (most common): cerebellum and medulla herniate through the foramen magnum, which can occlude the aqueduct and cause hydrocephalus. Usually leads to haemorrhage and necrosis
2) Subtentorial (rare): the occipital lobes herniate under the tentorium cerebelli, leading to midbrain compression
3) Subfalcin: cingulate gyrus herniates under the falx cerebri

Question 6

What are the 3 types of edema?

Answer 6

• Vasogenic
• Cytotoxic/ Cellular
• Interstitial/ Hydrostatic

Question 7

What is Vasogenic Edema?

Answer 7

Most common form
Damage to the vascular wall of the BBB increases permeability, allowing plasma proteins to leak into the intercellular space and rise in intracranial pressure

• Seen in trauma, inflammatory processes, tumours and infarcts
• Microscopically: perivascular spaces will be wide

Question 8

What is Cytotoxic/ Cellular Edema ?

Answer 8

Energy dependent Na+ and K+ pumps in the endothelial wall of the BBB allow Na+ to leak into the cells, fluid follows and intracellular swelling occurs

• Seen due to ischemia, toxic and metabolic disorders
• Microscopically: swells will be swollen

Question 9

What is Interstitial/ Hydrostatic Edema?

Answer 9

Intraventricular pressure increases, leading to the movement of CSF across the ependymal layer of cells that surrounds the ventricles. Fluid accumulates in the periventricular white matter leading to degeneration and loss of the white matter
EVentually, small pools may coalesce to form fluid filled cavities

Question 10

What is the definition of ischemia?

Answer 10

A restriction in blood supply to tissues, causing a shortage of oxygen that is needed for cellular metabolism (to keep tissue alive)

note: it only takes for a drop to <60% blood flow to lead to ischemia of the tissue

Question 11

What are the causes of ischemia?

Answer 11

• Global: severe loss of blood or blood pressure e.g. drug overdose, heart disease, severe anemia, hypovolemic shock
• Local: vascular occlusion (infarct)
• Primary vascular lesion: Atherosclerosis- very rare in animals though

Question 12

What are the predisposing factors for brain infarction? (6)

Answer 12

• Hypothyroid
• Hyperadrenocorticism
• Diabetes mellitus
• Hyperlipemia
• Hypertension
• Hypercoagulative state

Question 13

What are the causes to haemorrhage in the brain?

Answer 13

• Trauma
• Vascular: Inflammatory (vasculitis)
• Neoplastic
• Metabolic toxic

Question 14

Define Malacia

Answer 14

Malacia is abnormal softening of a biological tissue
Leukomalacia = brain white matter softening
polioencephalomalacia = brain grey matter softening

Question 15

What are the causes of Malacia? (4)

Answer 15

• Trauma
• Inflammatory disease
• Infarction
• Vascular disease: toxic, inflammatory

Question 16

What type of necrosis is seen in the brain?

Answer 16

Liquefactive Necrosis

as opposed to coagulative necrosis