APATH - STROKE

Question 1

List the four causes of ischaemia of brain tissue due to disturbances of the blood supply (4)

Answer 1

Thromboembolism, Rupture of wall, Pathology of wall (thickening), Disturbances of blood composition

Question 2

Name the anatomic feature that allows cerebral blood flow to continue in the presence of a section of atheroma in the carotid vessel (1)

Answer 2

Circle of Willis

Question 3

Describe the most common site of arterial aneurysms in the brain (2)

Answer 3

Base of brain on major vessels forming the arterial Circle of Willis.

Question 4

Describe the aetiology and pathogenesis of ischaemic stroke (7)

Answer 4

Degenerative arterial disease – arteriosclerosis in larger vessels (extracranial & intracranial) or small vessel disease.

Common/internal carotid artery plaques cause stenosis and thrombo-embolism.

Hypertension or diabetes – small perforating intracranial arteries of basal nuclei, internal capsule and brain stem. Collagen replacement of smooth muscle walls with or without fibrinoid necrosis – reduced vascular distensibility and narrowing of lumen. Infarcts caused are small necrotic areas – lacunes.

Emboli arising from heart and passing into cerebral circulation, especially with atrial fibrillation or other arrhythmias, valvular heart disease, post-myocardial infarction, cardiomyopathy.

Question 5

Explain the mechanism of a Left-sided cerebral infarct in a patient with atrial fibrillation and indicate the reason for the likely site of the infarct (4)

Answer 5

Decreased flow in atrial chamber due to AF  Increased thrombotic tendency

Early: No adhesion to wall of chamber  thromboembolism

Site: Middle cerebral artery because this is the straightest pathway into the brain.

Question 6

Explain why a patient with untreated ventricular fibrillation will not develop the same complication (½)

Answer 6

Because they die

Question 7

62 y/o smoker on anti-hypertensive drugs for the last six years. His left arm feels numb and weak which he attributes to stress. He decides to rest but wakes up later that night with a headache. His speech appears slurred and he is walking clumsily. O/E: Presence of atrial fibrillation with a large left atrial thrombus on ultrasound. Anticoagulation is initiated.

State which other lesion in the brain may be the cause of the stroke (1)

Answer 7

Cerebral haemorrhage

Question 8

Explain why the final clinical neurological deficit may be less severe than that which was found at initial presentation (2)

Answer 8

Surrounding oedema  dysfunction of brain but not cell necrosis

Ischaemia  membrane pump dysfunction  oedema and electrolyte imbalances

Question 9

List two (2) other cardiac diseases that could result in a cerebral infarct (2)

Answer 9

Cardiomyopathy, Bacterial endocarditis, etc.

Question 10

List three (3) predisposing factors for a stroke (1½)

Answer 10

Hypertension, diabetes, cardiac disease, smoking, atherosclerosis, polycythaemia, transient ischaemic attacks. History of previous stroke.

Question 11

List three (3) different mechanisms by which a stroke occurs (1½)

Answer 11

Thrombosis, embolism and haemorrhage

Question 12

Describe the macroscopic pathology seen in a cerebrovascular accident (4)

Answer 12

Soft, oedematous parenchyma; poor demarcation between grey and white matter; intra-cerebral and intraventricular haemorrhage; lacunes; late-cavity formation, discolouration due to haemosiderin deposition.

Question 13

Describe the microscopic pathology of a CVA (4)

Answer 13

Early – haemorrhage or ischaemic neuronal changes (red neurons with cytoplasmic microvacuolisation, cytoplasmic eosinophilia and pyknosis), subacute changes - (24 hours to 2 weeks) – necrosis, macrophage infiltration, vascular proliferation and later repair with gliosis and haemosiderin deposition.

Question 14

List two (2) complications of a CVA (1)

Answer 14

Any two of the following: decreased level of consciousness with risk of aspiration, bed sores, raised intra-cranial pressure, herniation, autonomic nervous system instability.

Question 15

List any six different important risk factors for “stroke” (6x½ = 3)

Answer 15

• History of previous stroke, Previous transient ischaemic attack(s), Systemic hypertension, Atrial fibrillation, Myocardial infarction, Prosthetic heart valve(s), Congestive cardiac failure, Rheumatic heart disease, Infective endocarditis, Diabetes mellitus, Polycythaemia etc
• Atherosclerosis, Hypertension, Diabetes mellitus, Heart abnormalities (e.g. AF), Previous TIA, Smoking/alcohol

Question 16

Name the two main varieties of stroke that may occur, and outline why it is important to distinguish between them in a patient (3)

Answer 16

• One mark for either of the choices listed under the two options given; one mark for the explanation:
• Atherothrombotic or embolic cerebral infarction (1)
• Subarachnoid or intracerebral haemorrhage (1)
• Must be differentiated because the treatment of the former may include anticogulants/fibrinolytics (1)
  Haemorrhagic and ischaemic. An ischaemic stroke can be treated with anticoagulants (heparin) whereas this would worsen the haemorrhagic stroke. The prognoses are also different for the two types.

Question 17

Briefly explain, with the aid of a diagram, the concept and significance of the “penumbra” in a case of stroke (3)

Answer 17

It represents the area around that of complete necrosis of neurons in an infarct (1); in it, the neurons are only injured, not killed (1) – so that, with appropriate/timely intervention (e.g. fibrinolytics) the ultimate size of the infarct may be reduced (1)

Red- ore neuronal loss occurring 0-20 mins/hrs? after occlusion.
Surrounding yellow area is the penumbra (20-25min/hrs?) with much more extensive neuronal loss.

Question 18

Identify the zones of a ring-enhancing lesion on a contrast-enhanced CAT scan, and explain what pathologic process causes the appearance of each zone identified (6)

Answer 18

Central black area: necrosis, no vessels thus no contrast
Ring of white contrast: disrupted vessels due to presence of tumour
Peripheral black zone due to oedema

Question 19

65 y/o man unable to talk or walk since 06h00 that day. He had experienced a brief period of paralysis of his hand about a week beforehand, but apart from increasing shortness of breath in the last month had otherwise been well. O/E BP of 170/100mm Hg., a pulse rate of 80 per minute and bilateral pedal oedema. Bruits were heard over the left common carotid artery and both renal arteries. Neurological examination confirmed the presence of right hemiplegia, with the leg relatively spared, and no aphasia. A urinary catheter was inserted for ease of nursing care.

Describe the macroscopic pathology that would most likely be found in the brain at autopsy of such a case. Indicate the site of this pathology (4)

Answer 19

Recent (1) infarction in the (1) left (1) MCA territory (1)

Question 20

State the most likely pathogenesis (4)

Answer 20

Atherothrombotic embolism, most probably from the (L) internal carotid.

Question 21

List 3 different predisposing factors (evident in the case) that could have contributed to the patient’s pathology (3)

Answer 21

Previous TIA, HPT, carotid atherosclerosis, cardiac failure, arrhythmia, valvular pathology, cigarette smoking, diabetes mellitus etc.

Question 22

Outline the prognosis you would expect in his case (4)

Answer 22

The students would not be expected to remember EXACT percentages

• In the short term (30-days) the mortality rate would be around 15% for an ischaemic stroke.
• This is considerably better than for haemorrhagic stroke, for which the 30-day mortality rate varies from 50-80% (82% for intracerebral and 46% for subarachnoid haemorrhages, respectively, to be exact) in the Framingham study; clinical surveys suggest there is often some fairly rapid initial recovery from an ischaemic (as opposed to haemorrhagic) event.
• But in the long term (at the end of the first year) worse – especially if there is an underlying cardiovascular lesion.

Question 23

68 y/o male patient, heavy smoker, known with hypercholesterolaemia and hypertension. His wife rushed him to the family GP after she noticed he had slurred speech and when he tried to walk to the bathroom he was clumsy and off balance. 30 minutes later in the GP surgery, he was completely unable to stand up, walk or talk. O/E expressive aphasia, R-sided weakness and sensory loss.

Explain how…
- Unilateral severe atheroma of the carotid artery may result in the above clinical scenario (2)

• Bilateral severe atheroma of the carotid artery may result in the above clinical scenario (2)

Answer 23

Severe atheroma  superimposed thrombus [Virchow’s triad]  embolization of atheroma into MCA territory

BILATERAL severe atheroma  thrombus  complete obstruction of ONE carotid but the opposite carotid cannot [via the Circle of Willis] compensate for the decrease of flow  stroke

Question 24

52 y/o moderately obese (BMI of 32) man, has smoked two packs of cigarettes a day for the past 38 years. He awakes one morning with weakness on his right side. He is slightly confused, sees double, and his speech is slurred. When he attempts to walk to the bathroom, he stumbles a few times and falls. O/E has a right hemiparesis, and diminished pinprick sensation and two-point discrimination on the right arm and right side of his head. His systemic BP 160/110. His deep tendon reflexes are brisk on the right and there is a Babinski reflex on the right. He has difficulty articulating, speaking only a few words and frequently responding with a single word. His ability to respond appropriately to complicated verbal commands is not impaired.
A CAT scan is performed and this shows the presence of an intracerebral bleed in the region of the basal nuclei, extending into the internal capsule.

Name (½) and describe the lesions that are likely to be found in the walls of the thalamostriate/ lenticulostriate vessels [penetrating cerebral arteries] in this patient (1½)

Answer 24

• Charcot Bouchard aneurysms/ microaneurysms [½]

- Vessels show damage to wall: Intimal thickening [½], medial fibrosis [½], rupture of elastic lamina [½]

Question 25

Name one sign that is most likely to be present on cardiac examination (1)

Answer 25

Heaving L apex [1] signs of hypertension