Stroke

Question 1

The Brain’s Blood Supply

Answer 1

It is extremely important that our brains remain oxygenated at all times!
We need a constant and reliable blood supply.
- Although the brain weighs ~2% of our body weight, it consumes about 15-20% of the body’s blood supply.

Question 2

What does Fresh blood bring

Answer 2

Fresh blood brings materials necessary for the brain to function proper.

• Oxygen, carbohydrates, amino acids, fats, hormones and vitamins go in;
• Carbon dioxide, ammonia, lactate and hormones go out.

Question 3

Circle of Willis

Answer 3

The Circle of Willis, named after Thomas Willis, is a collection of arteries that supplies blood to the brain and surrounding structures.
The arrangement of arteries creates anatomical
redundancy, which allows for collateral circulation of blood to the brainàIt’s a safety mechanism.
Therefore, if one part of the circle is blocked or narrowed, blood flow from other vessels can often preserve blood flow and avoid ischemia.

Question 4

What are the Circle of Willis made of

Answer 4

Composed of the following arteries:

• Internal carotid arteries
• Anterior cerebral arteries
• Anterior communicating artery
• Posterior cerebral arteries
• Posterior communicating arteries.

Question 5

Anterior circulation:

Answer 5

Supplies the anterior and medial parts of the brain

Question 6

Posterior circulation:

Answer 6

Supplies the posterior brain and cerebellum

Question 7

Communicating arteries:

Answer 7

forms Circle of Willis

Question 8

What is a stroke?

Answer 8

A stroke is a medical condition in which an abnormality of the vascular supply causes damage to the central nervous system.
The WHO defines a stroke as “neurological deficit of cerebrovascular cause that persists beyond
24 hours or is interrupted by death within 24 hours”

Question 9

There are two main types of strokes:

Answer 9

1. Ischemic(lackofbloodblow);

2. Hemorrhagic(causedbybleeding).

Question 10

Clinical Symptoms of a Stroke

Answer 10

Suffering from a stroke will produce very rapid and focal symptoms. Some symptoms may be permanent, others subside.
Usually occurs unilaterally.

Question 11

Common symptoms of a stroke are:

Answer 11

Common symptoms of a stroke are:
- Weakness in face and/or limbs;
- Numbness (loss of sensation);
- Aphasia or dysarthria;
- Vision loss;
- Headache
o Typically common with hemorrhagic stroke, not ischemic stroke
Rarely, patients may experience:
- Loss of consciousness;
- Pain;
- Abnormal movement.

Question 12

Remember FAST:

Answer 12

Remember FAST: Facial droop, Arm weakness, Speech difficulty = Time to call 9-1-1

Question 13

Ischemic Stroke

Answer 13

An ischemic stroke is (typically) caused by a blockage of arterial blood vessels.
There are 2 main ways that this could happen to you: Thrombosis and Embolism

Question 14

Thrombosis

Answer 14

Thrombosis: obstruction of a blood vessel by local blood clot;

Question 15

Embolism

Answer 15

Embolism: obstruction due to an embolus (traveling particle or debris in the bloodstream; G. wedge, plug) from elsewhere in the body;

Question 16

What happen in an Ischemic Stroke

Answer 16

Brain tissue ceases to function if deprived of oxygen for more than 60 – 90 seconds, and will suffer irreversible damage after ~3 hours of ischemia.
- Body not very good at generating ATP in absence of oxygen (lactateàlactic acidàacidosis);
- Leads to failure of energy-dependent processes in brain cells (e.g. ion pumping);
- Ultimately leading to apoptosis or necrosis.
An infarction is the tissue death (necrosis) caused by lack of blood supply to the affected area.

Question 17

Hemorrhagic Stroke

Answer 17

A hemorrhagic stroke refers to bleeding in or around the brain’s membranes, usually caused by a rupture of a blood vessel or abnormal vascular structure.
There are 4 main types: Epidural, Subdural, Sub-arachnoid, Intracerebral

Question 18

Epidural

Answer 18

Epidural*: between skull and dura matter;

Question 19

Subdural

Answer 19

Subdural*: between the dura matter and arachnoid space;

Question 20

Sub-arachnoid:

Answer 20

Sub-arachnoid: between arachnoid space and pia matter;

Question 21

Intracerebral

Answer 21

Intracerebral: bleeding within the brain itself. Either from the brain tissue (intraparenchymal hemorrhage) or from the brain’s ventricular system (intraventricular hemorrhage).

Question 22

What happens in an Hemorrhagic Stroke

Answer 22

In additional to neurological impairment due to loss of function in brain tissues, hemorrhagic strokes usually cause specific symptom:

• Severe headache;
• Dizziness;
• Seizures;
• Vomiting.

Question 23

Neuropathology of Infarction

Answer 23

The release of osmotically active substances (e.g. arachidonic acid, electrolytes, lactic acid, etc.) from necrotic brain tissue causes cerebral edema.

• Axons swelling can cause unravelling of myelin sheath;
• Neuroinflammatory response to release substances, forms glial scar around infarct; - Neovascularization occurs for ~2 weeks;

Question 24

Timeline for Neuropathology of Infarction

Answer 24

By 3-4 days, interstitial fluid accumulates in and around the infarct à this is the most dangerous period.
Cell death is caused by cerebral edema and herniations, not by loss of brain tissue.
Recovery of function can be achieved by restoration of perfusion, and the settling down of cerebral edema (acutely) and neuronal plasticity (long-term).

Question 25

Risk Factors Associated with Stroke

Answer 25

The biggest and most important risk factor for stroke is
hypertension* (high blood pressure), accounting for 35-50% of risk.
Other risk factors include: - Tobacco smoking;
- High blood cholesterol; - Diabetes mellitus;
- Lipids;
- Atrial fibrillation*; - Obesity;
- Age >75.

Question 26

Stroke Prevention

Answer 26

Blood pressure medication
- Aim is to reduce blood pressure and minimize hypertension risk.
Anticoagulation drugs
- Mainstay in stroke prevention for over 50 years; - Aspirin is highly effective.
Surgery
- Can remove atherosclerotic narrowing of carotid artery;
Diet
- Proper nutrition has the potential to decrease the risk of having a stroke by more than half.

Question 27

Imaging of Strokes

Answer 27

Diagnosis of a stroke is based on a physical exam, supported by imaging such as CT or MRI scan.
A perfusion CT scan is a specialized imaging technique that allows us to visualize blood flow.
We can see reduced blood flow in stroke patient, identify the subtype and cause of the stroke.

Question 28

Management of Stroke Patients

Answer 28

Treatment to try and recover lost function is called stroke rehabilitation and ideally takes place in a specialized stroke unit.
Physical therapy, occupational therapy, speech-language pathologists are all involved in the rehabilitation process.