WEEK 3: Clinical aspects of stroke Flashcards
What is Botswana’s ranking of stroke in the world?
What is the ranking of stroke in Botswana?
WHO 2017 – stroke deaths reached 2,450 or 7% of total deaths
98 per 100,000 of population
- Botswana ranks # 73 in the world.
- 3rd cause of death with rate of 98 per 100,000 population after HIV and AIDS and Corobnary heart diseases.
7% of our total death is due to STROKE
Stroke is an emergency and Time is Brain.
Define stroke.
Sudden onset of focal neurological deficit lasting more than 24 hours due to an underlying vascular pathology.
Define TIA.
Brief episode of neurological dysfunction caused by a focal disturbance of focal brain ischemia.
Clinical symptoms typically lasting less than 1 hour (< 24 hours).
Without evidence of infarction on scan.
Discuss the three main mechanisms causing ischemic strokes.
The three main mechanisms causing ischemic strokes are: (a) thrombosis, (2) embolism and (3) global ischemia (hypotensive) stroke.
All ischemic strokes do not neatly fall into these categories and the list of entities responsible for unusual stroke syndromes is very long.
However, strokes caused by vasospasm (migraine, following SAH, hypertensive encephalopathy) and some form of “arteritis” stand out among the more infrequent causes of stroke.
Ischemic Stroke (80%) “Brain Infarct”
- Thrombosis- mass of platelet or fibrin that forms locally in a vessel.
- Embolism- a piece of the thrombus that has broken free and carried toward the brain.
- Global Ischemia (Hypotensive) Stroke- profound reduction in systemic blood pressure producing ischemia in the “watershed areas.”
- Unusual Stroke syndromes
Discuss location of Ischemic Strokes.
- Anterior Circulation
*Occlusion of carotid artery involve cerebral hemispheres. - Posterior Circulation
*Vertebro-basilar artery distribution involve brainstem or cerebellum.
What is hemorrhagic stroke?
Discuss the causes of hemorrhagic stroke.
Discuss the 2 types of hemorrhagic stroke.
Hemorrhagic stroke occurs when a blood vessel in your brain leaks or ruptures.
Brain hemorrhages can result from a number of conditions that affect your blood vessels, including:
-Uncontrolled high blood pressure (hypertension)
-Weak spots in your blood vessel walls (aneurysms): Dilatation of the median layer of a blood vessel.
-A less common cause of hemorrhage is the rupture of an arteriovenous malformation (AVM) — an abnormal tangle of thin-walled blood vessels, present at birth
Hemorrhagic Stroke (15%)
- Subarachnoid
-Aneurysm (most common)
-Arteriovenous malformation - Intracerebral
-Hypertension (most common)
-Amyloid angiopathy in elderly
Discuss the mechanisms of thrombotic and embolic stroke.
THOMBOTIC: Blood clot blocks the flow of blood to the brain.
EMBOLIC: Fatty plaque or clot breaks away and flows to brain where it blocks an artery.
A thrombus or an embolus can occlude a cerebral artery and cause ischemia in the affected vascular territory.
It is often not possible to distinguish between a lesion caused by a thrombus and one caused by an embolus.
What happens when there is a reduction in blood flow to the brain?
State the normal volume of blood flow to the brain.
- Reduction in CBF (Less than 20ml/ 100g brain)
- Ischemia
- Inhibition of protein synthesis.
- Depletion of ATP
5.Release of glutamate neurotransmitter.
- Influx of calcium ions.
7.Opening of sodium and potassium ion channels.
- Formation of free radicals
- Cell Oedema and death
Normal CBF = 50-ml / 100g of brain/ minute.
IN SUMMARY….
Within an hour of hypoxic- ischemic insult, there is a core of infarction surrounded by an oligemic zone called the ___________where autoregulation is ineffective.
The critical time period during which this volume of brain tissue is at risk is referred to as the “window of opportunity” since the neurological deficits created by ischemia can be partly or completely reversed by reperfusions the ischemic yet viable brain tissue within a critical time period.
How long is this critical period?
Discuss Metabolic Derangements in CBF Changes
-Ischemic penumbra (IP)
-2 to 4 hours.
Discuss Metabolic Derangements in CBF Changes.
- Normal Range
- Oligemia
- Mild ischemia
- Moderate ischemia
- Severe ischemia
- Normal Range
Maintained by autoregulation;
Higher CBF in gray matter - Oligemia
Increased O2 extraction
May maintain normal CMRO2
Threshold of electrical failure - Mild ischemia
? Increased glycolysis
? ↓ protein synthesis - Moderate ischemia
PENUMBRA
Threshold of ionic failure - Severe ischemia
Anoxic depolarization
(↑ECF K & ↓ECF Ca)
Outline the modifiable risk factors of stroke.
Hypertension
Diabetes Mellitus
High Cholesterol
Heart Disease
Tobacco use
Physical inactivity
Hypercoagulopathy
Pregnancy, cancer, HIV
History of carotid bruit
Atrial Fibrillation
Outline the non-modifiable risk factors of stroke.
Age
Gender
Race
Previous Stroke and TIA
Hereditary / Family History
Discuss the blood supply to the brain.
The brain receives its blood supply from two main sources: the anterior circulation and the posterior circulation.
These two systems are connected by communicating arteries, ensuring continuous blood flow to the brain.
Anterior Circulation:
This system is primarily supplied by the internal carotid arteries (ICAs), which branch into the anterior cerebral artery (ACA) and the middle cerebral artery (MCA).
The ACA supplies blood to the medial surface of the frontal and parietal lobes, as well as the corpus callosum.
The MCA is the largest branch of the internal carotid artery and supplies blood to the lateral aspects of the frontal, temporal, and parietal lobes, including important areas such as the motor and sensory cortices, language centers, and areas involved in higher cognitive functions.
- Posterior Circulation:
This system is primarily supplied by the vertebral arteries, which join to form the basilar artery.
The basilar artery then gives rise to branches such as the posterior cerebral arteries (PCAs).
The PCAs supply blood to the occipital lobes, inferior temporal lobes, and parts of the thalamus and midbrain.
The posterior circulation is responsible for supplying blood to the brainstem and the cerebellum as well.
Describe the Common Signs and Symptoms of stroke in the following regions.
- Anterior Cerebral artery
- Middle Cerebral artery
- Posterior circulation
ACA (Anterior Cerebral Artery):
*Paraplegia:
Weakness or paralysis affecting the lower limbs, typically on the contralateral side of the brain lesion.
*Abulia:
Reduced initiative, motivation, or spontaneity.
*Motor aphasia:
Difficulty in expressing language verbally, often accompanied by intact comprehension.
*Behavioral changes:
This can include a wide range of alterations in mood, personality, or social behavior.
- MCA (Middle Cerebral Artery):
*Contralateral hemiplegia: Weakness or paralysis affecting the upper and lower limbs on the side opposite the brain lesion.
*Homonymous hemianopsia: Loss of vision in the same visual field of both eyes.
*Global aphasia: Severe impairment in both expressive and receptive language functions.
*Gerstmann syndrome: Characterized by a constellation of symptoms including acalculia (difficulty performing arithmetic), finger agnosia (inability to distinguish fingers), right-left disorientation, and apraxia (difficulty executing purposeful movements).
- Posterior Circulation:
*Dizziness: Sensation of lightheadedness, imbalance, or spinning.
*
Dysarthria: Difficulty articulating speech due to weakness or poor coordination of the muscles involved in speech production.
*Ataxia: Lack of coordination of voluntary muscle movements, affecting balance and gait.
*Dysphagia: Difficulty swallowing.
Discuss Symptoms of Intracerebral hemorrhage (ICH).
SAH- asymptomatic before rupture, presents with seizure, neck stiffness, focal neurologic deficits, severe headache.
ICH- history of Hypertension, seizures, vomiting, headaches
