Lecture 6 - Introduction To Stroke

Question 1

Why is it important to study stroke?

Answer 1

It is the 3rd leading cause of death. If it doesn’t kill, it can majorly affect the lives of survivors.
To understand the impact a stroke has on the healthcare system, family dynamics, work etc.
To increase our understanding of the pathophysiology of stroke.
To develop effective prevention and intervention.

Question 2

What are 3 main components that make up the brain and what are their functions?

Answer 2

Brainstem - connects brain to the top of the spine and is in charge of lots of important functions such as heart function and breathing.
Cerebellum - sits at the back and bottom of the brain and is involved in balance and movement.
Cerebrum - the largest part of the brain and consists of 4 lobes which work together to perform functions.

Question 3

What are the 4 lobes that make up the cerebrum and what are their functions?

Answer 3

Frontal lobe (at the front of the brain) - involved in motor cortex, judgement, inhibition, personality, emotions and language production.
Temporal lobe (at the bottom in the middle/back) - involved in auditory perception and memory.
Parietal lobe (at the top near the back) - involved in sensory processing and orientation.
Occipital lobe (at the back) - involved in vision.

Question 4

Why is blood supply to the brain important?

Answer 4

Most of the brain consists of neurons and specialised cells. These are interconnected and rely on oxygen and glucose to function which is supplied by the blood.
These cells are in charge of what we think, how we feel, how we move etc.

Question 5

What are the main arteries that lead to the brain?

Answer 5

The carotid arteries and the vertebral arteries.

Question 6

How can the blood circulation in the brain be divided?

Answer 6

Anterior supply (front) which the carotid arteries give rise to.
Posterior supply (back) which the vertebral arteries give rise to.
These arteries join to form the basilar arteries.

Question 7

What is the Circle of Willis?

Answer 7

The basilar arteries split into 2 to form a circle known as the Circle of Willis.
This circle gives rise to the posterior cerebral artery, middle cerebral artery and the anterior cerebral artery which supply blood to the lobes in the brain.
There are 2 other important arteries in Circle of Willis which are the internal carotid artery and common carotid artery.
The circle of Willis is really specialised because if there is a blockage in one of the arteries, there is still another way for the blood to go around or the brain can receive collateral supply from another vessel.

Question 8

What blood vessels/arteries supply blood to which parts of the brain?

Answer 8

The frontal lobe is supplied by the anterior cerebral artery and the middle cerebral artery.
The temporal lobe is supplied by the posterior cerebral artery.
The parietal lobe is supplied by the middle cerebral artery.
The occipital lobe is supplied by the posterior cerebral artery.
The brainstem is supplied by the pontine branches and anterior spinal artery.
The cerebellum is supplied by the posterior inferior cerebellar artery, inferior cerebellar artery and the superior cerebellar artery.

Question 9

Which artery is the most commonly blocked?

Answer 9

The middle cerebral artery - important because it supplies such a large area.

Question 10

What is a stroke?

Answer 10

A stroke is a brain attack, which results in an interruption to the blood supply to the brain. This interruption leads to cell death due to the cells not receiving oxygen and glucose from the blood.
They can happen in any part of the brain and affect how our brain functions.

Question 11

What is an ischaemic stroke and what are the 3 types?

Answer 11

An ischaemic stroke is a blockage of blood such as a clot.
These are categorised into cerebral thrombosis, cerebral embolism and systemic hypoperfusion.

Question 12

What is a haemorrhage and what are the 3 types?

Answer 12

A haemorrhage is a bleed into the brain e.g. from a burst blood vessel.
The 3 types are intracerebral haemorrhage, subarachnoid haemorrhage and epidural haemorrhage.

Question 13

What is a transient ischaemic attack?

Answer 13

A TIA is a ‘mini stroke’ where the blood supply to the brain is temporarily blocked.
They usually resolve themselves (e.g. blood clot dissolves itself) but can be a warning sign of a major stroke.
Can have same symptoms as an ischaemic stroke and symptoms usually last less than 24 hours.

Question 14

How does a thrombotic stroke occur?

Answer 14

Occurs when the blood clot has formed in one of the major arteries leading to the brain. This blocks the blood supply to the surrounding region and the area that has lost blood supply can lead to an infarction (cell death).

Question 15

How does an embolic stroke occur?

Answer 15

A blood clot forms somewhere else in the body and then travels around the body in the bloodstream and lodges in the brain.
Blood clot forms at the donor site and ends at the recipient site.
It can often occur due to atherosclerosis (fatty build up in arteries that breaks off and leads to a clot).

Question 16

How does systematic hypoperfusion occur?

Answer 16

There is a general reduction in circulating blood volume resulting in inadequate supply of blood to body tissues.
It often occurs due to reduced cardiac output or problems with heart functions.
It affects the entire body, not just the brain.
Could affect different parts of the brain or the entire brain.

Question 17

How does a haemorrhagic stroke occur?

Answer 17

Occurs when parts of the brain are no longer receiving blood.
Bleeding tears and disconnects vital nerve centre and pathways. The blood leaks into the brain under pressure and forms a localised blood collection called a hemotoma.
Can occur due to an aneurism, high blood pressure and abnormalities in how the arteries are formed.

Question 18

How does a intracerebral haemorrhage occur?

Answer 18

A blood vessel has burst deep within the brain and lead to bleeding in the brain.

Question 19

How does a subarachnoid haemorrhage occur?

Answer 19

A blood vessel has burst on the surface of the brain which can increase pressure between the skull and brain tissue.

Question 20

How does an epidural/subdural haemorrhage occur?

Answer 20

A bleed in the outer membrane of the brain (in the dura mater).
Epidural = bleed of an artery.
Subdural = burst of a vein (carries blood away from the brain).

Question 21

What does the left hemisphere control?

Answer 21

Sensory stimulus from the right side of the body.
Motor control of the right side of the body.
Speech, language and comprehension.
Analysis and calculations.
Time and sequencing.
Recognition of words, letters and numbers.

Question 22

What does the right hemisphere control?

Answer 22

Sensory stimulus from the left side of the body.
Motor control of the left side of the body.
Creativity.
Spatial ability.
Context/perception.
Recognition of faces, places and objects.

Question 23

What are generalised symptoms of a stroke?

Answer 23

Headache, nausea etc. but it is hard to say if this is from a stroke or other factors.

Question 24

What would a stroke in the brainstem mean?

Answer 24

The brainstem is involved in core bodily functions so disruption to blood supply could result in difficulty swallowing/choking and issues with heart function. It would also result in paralysis on both sides.
It is quite uncommon but very fatal.

Question 25

What are the warning signs of a stroke (FAST)?

Answer 25

Face drooping (commonly left side). Arm weakness (opposite side to where the stroke occurred). Speech difficulty (may be confused, not able to follow conversation or not be able to speak). Time to call. Usually these signs and symptoms come on suddenly. You may also have difficulty seeing or get migraines. These warning signs are typically associated with an ischaemic stroke.

Question 26

Why would numbness or weakness occur during a stroke?

Answer 26

Numbness may happen if the stroke affects the primary somatosensory cortex (part of your brain that allows you to feel stuff) - it may lead to a change in sensation e.g. numbness. Weakness may develop if the stroke affects to motor cortex (the area that controls movement). These areas are close together so it is likely they will both occur together.

Question 27

Why would someone have trouble speaking/understanding others during a stroke?

Answer 27

The stroke may have affected parts of the brain involved in speech production - these areas receive a blood supply from the MCA. Broca’s area (frontal lobe) - involved in speech production. Wernicke’s area (junction of temporal and parietal lobe) - involved in understanding speech and producing meaningful speech. Reduced blood flow to either of these areas may lead to this symptom and the individual may not be able to tell anything is wrong with their speech.

Question 28

Why might someone have problems with vision during a stroke?

Answer 28

It could be due to reduced blood flow to the parts of the occipital lobe area of the brain. Or could involve difficulties with visual perception, which means any other part o the brain that feeds this info to the occipital lobe region could be affected.

Question 29

Why might someone experience sudden dizziness or loss of balance/coordination during a stroke?

Answer 29

Can indicate reduced blood flow to parts of the parietal lobe (involved in orientation). Or it could indicate a stroke in the cerebellum, but this would be accompanied by other symptoms specific to the cerebellar.

Question 30

Why might a sudden severe headache occur during a stroke?

Answer 30

Common in a haemorrhagic stroke and is a result of a bursting blood vessel. A burst blood vessel leads to swelling so the brain starts to push against the skull and this leads to a severe headache.

Question 31

What is the Bamford Stroke Classification?

Answer 31

It is a classification system for ischaemic stroke, which categorises strike based on the initial presenting symptoms and clinical signs. It can help identify where the stroke might have occurred in the brain.

Question 32

What is total anterior circulation stroke and what criteria needs to be met?

Answer 32

TACS is where the majority of the blood flow towards the front of the brain is affected. Consists of a large cortical stroke in the middle/anterior cerebral artery areas. Criteria = all 3 of the following: - Unilateral weakness (and/or sensory deficit). - Homonymous hemianopia. Higher cerebral dysfunction such as dysphasia, visuospatial disorder etc.

Question 33

What is homonymous hemianopia?

Answer 33

A visual field defect affecting either the 2 right or 2 left halves of the visual fields of both eyes. Causes people to not notice relevant objects on the affected side.

Question 34

What is higher cerebral dysfunction?

Answer 34

Cognitive and behavioural consequences resulting from brain damage. Can include attention deficits, memory disorders, executive dysfunction, dysphasia (affects ability to produce language).

Question 35

What is partial anterior circulation stroke and what criteria needs to be met?

Answer 35

PACS is a cortical stroke in the middle/anterior cerebral artery areas. It is a milder version of TACS. Criteria = involves 2 of the following: - Unilateral weakness (and/or sensory deficit). - Homonymous hemianopia. - Higher cerebral dysfunction. Or it can involve either sensory deficit in just one arm or leg and higher cerebral dysfunction.

Question 36

What is lacunar syndrome and what criteria needs to be met?

Answer 36

LACS is a subcortical stroke that occurs secondary to small vessel disease (comes after). There is no loss of higher cerebral functions. Small vessel disease involves the smaller blood vessels within the brain - to is characterised by structural changes in the brains vasculature. Criteria = one of the following: - Pure sensory stroke. - Pure motor stroke. - Sensorimotor stroke. - Ataxic hemiparesis.

Question 37

What is ataxic hemiparesis?

Answer 37

Usually caused by lacuna infarction in the pons (part of the midbrain that relays sensory info to the cerebellum). It leads to muscle weakness and loss of voluntary coordination of muscle movement.

Question 38

What is posterior circulation syndrome and what criteria needs to be met?

Answer 38

POCS means the stroke affects the back area of the brain which includes the brainstem, cerebellum and occipital lobes. Criteria = one of the following needs to be present: - Cranial nerve palsy (lack of function of a nerve) and a contralateral (opposite side of affected side) motor/sensory deficit. - Bilateral motor/sensory deficit (affects both sides of body). - Conjugate eye movement disorder (e.g. horizontal eye palsy) (inability to move both eyes together). - Cerebellar dysfunction (e.g. vertigo, ataxia). - Isolated homonymous hemianopia.

Question 39

What factors affect the severity of a stroke?

Answer 39

Which blood vessel was affected, which brain region was affected, the timeframe, age, and other health problems.

Question 40

Why is it important to know the symptoms and warning signs of a stroke?

Answer 40

Kothari et al. (1997): Almost 40% of patients admitted with a possible stroke did not know the signs, symptoms or risk factor of a stroke. And around 50% did not know a stroke was due to an injury to the brain. Education programs that talk about the warning signs and symptoms are stroke may be helpful.