Pathology of Cerebrovascular Disease

Question 1

what is unusual about the veins and arteries within the brain?

Answer 1

the veins of the brain do not accompany the arteries which is unusual in the body- the arteries are arranged in the circle of Willis and there are large venous sinuses within the dura

Question 2

what is ischaemia?

Answer 2

a relative lack of blood supply in a tissue or organ

Question 3

what is hypoxia?

Answer 3

lack of oxygen

Question 4

how do hypoxia and ischaemia relate?

Answer 4

a lack of blood flow can cause a lack of oxygen if it lasts long enough but you can have hypoxia without ischaemia eg in high altitudes

Question 5

what is a stroke?

Answer 5

focal neurological deficit due to disruption of blood supply

Question 6

what causes a stroke?

Answer 6

changes in the vessel wall, blood flow or blood constituents which cause interruption of supply of oxygen and nutrients, causing damage to brain tissue

Question 7

what are changes in the vessel wall?

Answer 7

abnormalities of the wall eg atheroma or vascultis, outside pressure like strangulation, spinal cord compression or compression of veins

Question 8

what are changes in blood flow and pressure?

Answer 8

eg decreased blood flow or increased BP bursting vessels

Question 9

what are the changes in blood constituents?

Answer 9

thrombosis of arteries and rarely veins, bleeding due to anticoagulation, reduced platelets and clotting factors

Question 10

what are the 3 main causes of localised interrupted blood supply?

Answer 10

atheroma and thrombosis of artery causing ischaemia, thromboembolism, ruptured aneurysm of cerebral vessel causing haemorrhage

Question 11

describe how atheroma and thrombosis of artery causes ischaemia.

Answer 11

partially narrowed artery due to atheroma and then severely narrowed artery due to thrombosis (platelets and fibrin) on top of the atheroma causes poor blood flow leading to ischaemia

Question 12

what usually happens with ICA thrombosis?

Answer 12

typically get ischaemia in the MCA territory but can affect elsewhere

Question 13

what does a TIA cause?

Answer 13

reversible ischaemia so that the tissue is still viable

Question 14

what happens if symptoms are longstanding (>24)?

Answer 14

irreversible ischaemia causing localised brain death= infarct

Question 15

describe what happens in a thromboembolism causing ischaemia.

Answer 15

eg left atrium its connected directly to outflow of left side of the heart so if thrombosis of the left atrial appendage breaks off it will embolise to aorta and possibly the carrots (or other) arteries- the thrombus will embolise until it finds a narrowing which blocks the artery causing ischaemia and an ischaemic stroke (similar pathology to atheroma and thrombosis ischaemia but underlying cause is from the heart)

Question 16

describe the ruptured aneurysm of cerebral vessel causing haemorrhage.

Answer 16

beyond the carotid and vertebral arteries, the cerebral arteries have thin walls (as you don’t want them to contract) causing weakening of wall and hypertension causes aneurysm to form which causes haemorrhage and decreased blood flow distally to the brain due to spasm of the artery (as any vessel that bleeds undergoes spasm)

Question 17

what are the 2 common sites if ruptured vessels causing haemorrhage stroke?

Answer 17

basal ganglia- micro aneurysms form in hypertensive patients which suddenly burst and the patients will have a stroke and in the circle of Willis- berry aneurysm forms in hypertensive patients or both of these areas can rupture leading to haemorrhage

Question 18

what are the 3 generalised causes of interrupted blood supply or hypoxia?

Answer 18

low O2 in the blood eg CO2 poisoning, near drowing or respiratory arrest, inadequate supply of blood eg cardiac arrest, hypotension or brain swelling (eg trauma), rarely= inability to use O2 eg cyanide poisoning

Question 19

how does hypotension cause generalised interrupted blood supply and/or hypoxia leading to brain injury?

Answer 19

coronary artery bypass with prolonged period of hypotension during operation - patient is kept oxygenated by ventilation and central arterial territories are perfused better and the watershed zones are poorly perfused leaving zonal pattern of ischaemia dn infarction at the interface of territories (ie the watershed zones)

Question 20

how does cardiac arrest cause generalised interrupted blood supply and/or hypoxia leading to brain injury?

Answer 20

MI followed by CA and is then resuscitated but during minutes between there is no circulation to brain and no oxygen in blood so the brain is deprived of blood flow and O2 which causes grey matter necrosis= smooth cortical necrosis

Question 21

what are watershed infarcts?

Answer 21

zones of infarction at the interface of artery perfusion territories