Week 38- Focal brain dysfunction: Stroke Flashcards

1
Q

What is the main form of cerebral vessel control?

A

Local autoregulation play the major role

Very small role by Neural control

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2
Q

What are some autoregulation factors within cerebral vessels?

A

Metabolic:
rise in CO2, fall in pH and pO2 (similar to coronary control)
- Adenosine (ATP breakdown)
- K+ (from action potentials due to neuronal activity

Local:
vasoactive substances from astrocytes (NO)

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3
Q

How does cerebral blood flow change with Arterial pressure?

A

Is relatively steady (except for increases to about 60)

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4
Q

What allows the cerebral blood flow to remain steady?

A

Autoregulation reassures adequate CBF during fluctuations of (arterial pressure)

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5
Q

What is the mechanism of NO release by astrocytes?

A
Increased neuronal activity
Increased glutamate release
Glutamate uptake by astrocytes
Astrocytes release NO
NO drives local vasodilation and increase in blood flow
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6
Q

What is stroke?

A

Ischaemic event leading to lack of blood supply to the brain:
Deficit of Oxygen
Deficit of glucose
Lack of waste removal

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7
Q

What is the two major types of stroke?

A

Ischaemic (80%) –> interrupted blood flow in a cerebral vessel
Haemorrhagic (20%) –> bleeding into brain tissue out of a cerebral vessel

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8
Q

What is blood supply so important to the brain?

A

No storage of crucial glucose and oxygen in the brain –> needs constant flow

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9
Q

What is a major cause of ischaemic stroke?

A

Embolism –> thrombus from other region of the body and travels to the brain

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10
Q

What side of the heart results in more thrombi and emboli from stroke?

A

Left side

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11
Q

What cardiovascular abnormalities may cause ischaemic stroke?

A
Intracranial atherosclerosis
Penetrating artery disease
Carotid plaque with arteriogenic emboli
Flow reducing carotid stenosis
Aortic arch plaque
Cardiogenic emboli
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12
Q

How can causes of haemorrhagic stroke be described in two categories?

A

Increased pressure
OR
Decreased strength of the vessel

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13
Q

What cardiovascular abnormalities may cause haemorrhagic stroke?

A
Hypertension
Aneurysms
Arteriovenous malfunctions
Head injury
Blood dyscrasias -->is a nonspecific term that refers to a disease or disorder, especially of theblood.
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14
Q

What happens in the brain tissue after stroke at time points: 30s, 1min, 5min, 7mins?

A

30 seconds –> metabolism alters and slows

1 minutes –> neurons stop functioning

5 minutes –> anoxia leads to the start of infarction:

- Vasodilation and blood stasis
- Oedema 
- Necrosis --> softening, liquefaction, tissue removal

7 minutes –> excitotoxic process begins to kill neurons

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15
Q

What is the cellular mechanism behind excitotoxic lesions?

A

Glucose/ O2 shortage gives two sequences of events via Loss of ATP and excess lactic acid

1. Loss of ATP --> Sodium potassium pumps stop functioning
- K+ escapes, Na+ enters and the cells depolarise
- Ca2+ released from intracellular stores AND calcium enters the cell via voltage- gated channels
- Ca2+ overload
- Calcium activates proteolytic and lipolytic enzymes, water also enters into the cells (following Ca2+) AND neurotransmitter Glutamate release
- Autolysis via activated proteins begins --> Cell swells and rupture from water excess

2. Lactic acid increase --> fall in pH
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16
Q

What is the effect of neurotransmitter release (glutamate) during excitotoxic shock?

A

Glutamate released by calcium overload feeds back to increase calcium through voltage gated and ligand gated calcium channels

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17
Q

What is the two key anatomies of a stroke region?

A

Core –> dead, infarcted brain tissue

Penumbra –> threatened, potentially salvageable tissue surrounding the infarct core soon after stroke

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18
Q

What are some signs and symptoms of stroke?

A

Sudden onset
Combination of sensory, motor and cognitive deficits
Commonly:
- Loss of sensation and numbness in one side of the body
- Hemiplegia (same side as sensory disorder) and muscle weakness of the face (droop)
- Initial reduction of muscle tone –> replaced by muscle rigidity/spasticity and hyperreflexia on the same side

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19
Q

Why do clinical signs appear on the opposite side of the body compared to the side of the brain with the stroke?

A

There is cross-over of both sensory and motor pathways in the brain

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20
Q

What determines clinical signs in stroke?

A

Location and extent of the stroke (core and penumbra)

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21
Q

What are some signs of stroke occurring in the brainstem?

A

Altered smell, taste, hearing or vision
Decreased sensation on the face
Ptosis (drooping eyelids) and weak ocular muscles
Facial muscle weakness (cant smile)
Weakness in tongue
Decreased reflexes (swallowing, pupils to light)
Possibly altered respiration

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22
Q

What are some signs of stroke affecting the cerebellum?

A
Altered equilibrium (not sitting/standing symmetrical)
Altered coordination of movements
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23
Q

What time points would CT and MRI show stroke?

A

CT–> no significant changes in first 24hours

MRI–> can see as early as 15mins post stroke

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24
Q

Why is CT used in ED for suspected stroke?

A

To check for haemorrhage NOT for signs of stroke

–> if no haemorrhage –> thrombolytics etc can be given to dissolve clot and return blood flow

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25
What are the main treatments and managements of strokes (mainly embolic)?
Thrombolysis Thrombectomy Body cooling
26
What is CSF?
A filtrate from the blood
27
How often is CSF replaced?
Totally replaced in 5-7 hours
28
What path does CSF flow in the body?
``` Chorioid plexus of the lateral ventricles 3rd ventricle Cerebral aqueduct 4th ventricle Foramina Magendi and Luska Subarachnoid space Arachnoid granulations Sagittal sinus ```
29
What is the primary roles of CSF?
Cushioning | Bringing nutrients and taking waste away
30
What produces CSF?
Secreted by the chorioid plexus --> a network of ependymocytes located in the lateral ventricles
31
How does the ependymocytes drive water from the blood for CSF?
Transport of Na+ Cl- and HCO3 from the plasma to the ventricle creating an osmotic gradient to drive H2O
32
What is normally present and not present in CSF?
Present --> Clear H2O, Glucose, small amount of protein | Not present --> WBC, large amounts of protein
33
What is elevated protein in CSF a sign of?
Damage to the blood-brain barrier
34
What is cranial volume?
Volume of the brain space --> inside the skull = volume of brain + volume of blood + volume of CSF --> its value is constant
35
What is the equation for cerebral perfusion pressure?
CCP = mean arterial pressure (MAP) - intracranial pressure (ICP)
36
From the equation for cerebral perfusion pressure what would be the impact of a rise in ICP?
Reduction in cerebral perfusion
37
What is the mechanism behind increase ICP during ischaemic stroke vs haemorrhagic stroke?
Ischaemic --> brain oedema drive increased ICP Haemorrhagic --> extra blood within skull drives an increase in ICP
38
What is atherosclerosis?
Progressive, degenerative arterial disease that leads to the occlusion of affected vessels reducing the blood flow through them
39
What category of disease is atherosclerosis?
Inflammatory disease
40
What is atherosclerosis characterised by?
Formation of lipid rich plaques in the vessel walls of medium and large sized arteries
41
What are risk factors for atherosclerosis?
Smoking, diabetes, hypertension, hyperlipidaemia
42
What is thought to be the key initiator of atherosclerosis?
Endothelial injury
43
What is Atheroma?
Degeneration of the walls of the arteries caused by accumulated fatty deposits and scar tissue, and leading to restriction of the circulation and a risk of thrombosis also known as the fatty material which forms deposits in the arteries.
44
What are the constitution and modifiable risk factors of atherosclerosis?
Constitutional --> genetics, age, gender | Modifiable risk factors --> hyperlipidaemia, hypertension, smoking, diabetes
45
What is the mechanism of pathogenesis of atherosclerosis?
1. Endothelial injury and dysfunction --> increased vascular permeability, leukocyte adhesion and thrombosis 2. Accumulation of lipoproteins --> mostly LDLs in vessel walls 3. Monocyte adhesion to endothelium --> migrate into the intima and transformation into macrophages and foam cells 4. Platelet adhesion 5. Factors released from platelets, macrophages and vascular cell walls inducing smooth muscle cell recruitment 6. Smooth muscle cell proliferation, extracellular matrix production and recruitment of T cells 7. Lipid accumulation both inside and outside cells
46
What is the impact of haemodynamic changes in atherosclerosis?
Turbulent blood flow --> important in atherogenesis and plaque formation Non-turbulent flow is actually protective against atherosclerosis through gene induction in endothelial cells
47
How are lipids transported in the blood stream?
Bound to apoproteins
48
What are fatty streaks composed of?
Lipid filled foamy macrophages
49
What is the impact of atherosclerotic disease involving the heart?
MI, angina
50
What is the impact of atherosclerotic disease in/ involving the Brain?
Cerebral infarction (stroke)
51
What is the impact of atherosclerotic disease in/ involving the aorta?
Aneurism
52
What is the impact of atherosclerotic disease in/ involving the peripheries?
Gangrene of the legs etc
53
What is the impact of atherosclerotic disease in/ involving the Kidneys?
Atherosclerotic renovascular disease (ARVD)
54
How many people will have a stroke in their lifetime in Australia?
1 in 4
55
How many strokes occur each year in Australia?
50000ish and the number is expected to rise to 100,000 by 2050
56
What are the risk factors for ischaemic stroke?
``` Hypertension Diabetes mellitus Cardiac disease Hypercholesterolemia Past TIAs Carotid stenosis Obesity Sickle cell disease Use of oral contraceptives ```
57
What are the risk factors for haemorrhagic stroke?
``` Advanced age Hypertension (up to 60% of cases) Previous history of stroke Alcohol abuse Use of illicit drugs (eg, cocaine, other sympathomimetic drugs) ```
58
What are Focal neurological signs?
CNS signs are impairments of nerve, spinal cord, or brain function that affects a specific region of the body, e.g. weakness in the left arm, the right leg, paresis, or plegia.
59
What is the significance of focal neurological signs during examination?
They can be used to identify a particular area which has potentially been damaged
60
Symptoms of ischaemic stroke?
The symptoms of an ischemic stroke depend on which parts of your brain are affected. They can include things like: Sudden numbness or weakness of your face, arm, or leg, often on one side of the body Confusion Problems speaking or understanding others Dizziness, loss of balance or coordination, or trouble walking Vision loss or double vision
61
Symptoms of haemorrhagic stroke?
``` Haemorrhagic stroke symptoms usually increase gradually over minutes or a few hours, although a subarachnoid haemorrhage may come on suddenly. Some things that can happen: Intense headache that some people describe as "the worst headache they've ever had" Confusion Nausea or throwing up Sensitivity to light Problems with vision Passing out Neck stiffness ```
62
What is a cortical stroke?
A stroke affecting the cerebral cortex
63
What is a subcortical stroke?
Strokes affecting the inner structures of the brain
64
How does a cortical stroke typically present?
Strokes affecting the cerebral cortex (i.e. cortical strokes) classically present with deficits such as neglect, aphasia, and hemianopia.
65
How does a subcortical stroke typically present?
Subcortical strokes affect the small vessels deep in the brain, and typically present with purely motor hemiparesis affecting the face, arm, and leg.
66
What is speech?
The actual process of producing sound
67
What is language?
Deals with meaning/understanding behind the spoken words.
68
What are neurological pathways involved in speech production?
1. Broca's area --> speech production | 2. Motor cortex --> muscle movements required for speech
69
What is the neurological pathway of understanding language?
1. Auditory cortex (for auditory information), Visual cortex (reading, sign language) 2. Wernicke's area (language comprehension) 3. Information travels via Arcuate fasciculus (nerve fibres) to the Broca's area
70
Where is Wernicke's are located in the brain?
posterior section of the superior temporal gyrus (STG)
71
Where is Broca's area located in the brain?
Frontal lobe
72
What kind of aphasia may be produced by damage to Wernicke's area?
Produces problems with comprehension: | Sensory aphasia/Receptive aphasia (these 2 are the same thing)
73
What kind of aphasia may be produced by damage to Broca's area?
Speech production problems: | Expressive/motor/non-fluent aphasia (all these 3 are the same thing)
74
Where is the swallowing centre in the brain?
Medulla (in the brain stem)
75
What is the neurological pathway of swallowing?
Precentral gyrus, frontal gyrus and posterior-inferior gyrus initiate (in voluntary) Information travels to the brainstem (medulla) Medulla relays signal to swallow via cranial verves: Trigeminal (5) Facial (7) Glossopharyngeal (9) Vagus (X) Hypoglossal (12)
76
What are the stages of swallowing?
Oral phase Pharyngeal phase Oesophageal phase
77
What are the two areas that are subject to thrombosis?
Venous | Arterial
78
What are the risk factors of venous thrombosis?
``` History of DVT (family or patient) Hormone therapy/ contraceptive pill Pregnancy Vein injury (surgery/trauma etc) Immobility Inherited blood clotting disorder Older age Smoking Overweight/obesity Health conditions (cancer, heart disease, lung disease etc) ```
79
What are the risk factors of arterial thrombosis?
``` Smoking Diabetes High blood pressure High cholesterol Lack of activity (immobility) Obesity Family history of arterial thrombosis Older age ```
80
What are some neurological signs of clotting?
``` Symptoms on the opposite side of the body to where the clot has impacted the brain Facial droop Weakness Headaches Confusion Slurred speech Vision changes Loss of consciousness Dizziness ```
81
What are some signs of clotting in the venous system?
``` Venous blood clots occur most commonly in the arms and legs swelling of the affected area Warmth Redness pain ```
82
What are some signs of clotting in the arterial system?
``` Pain Peripheral clots can give pallor Weakness Loss of sensation paralysis ```
83
What is a stroke unit?
A stroke unit is an organized in-hospital facility that entirely (or next to entirely) is devoted to care for patients with stroke. It is staffed by a multidisciplinary team with special knowledge in stroke care.
84
What is the role of stroke rehabilitation?
Helping patients relearn lost skills due to stroke damage
85
What are stroke scores?
A scoring system based on presenting stroke symptoms
86
How is a stroke scoring system valuable in evaluating stroke?
Can help guide where the stroke may be occurring and the extent of damage/severity
87
What type of stroke typically only impacted motor functions in stroke?
Lacunae