Cerebrovascular Diseases Flashcards by Victor Redmon

What regions of the brain are supplied by:

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Circle of Willis

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What is hypoxia?

Deprivation of O₂ in the brain

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What are the 3 mechanisms of hypoxia?

What are some examples?

Low level of O₂ in blood
- Respiratory arrest, near drowning, severe anemia, CO poisoning
Low blood flow to tissue (ischemia)
- Cardiac arrest, vessel obstruction, increased intracranial pressure
O₂ utilization by tissue is impaired
- Cyanide poisoning

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Which statement is true?

Ischemia causes more damage than hypoxia.
Hypoxia causes more damage than ischemia.

Ischemia causes more damage than hypoxia.

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What is global ischemia?

Systolic pressure <50 mmHg
Generalized reduction in cerebral perfusion, usually due to cardiac arrest, shock or severe hypotension
Clinical outcome dependent upon severity & duration of ischemia

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With global ischemia, where is the damage most severe? What can this cause?

Brain damage is most severe in watershed/borderzone territories
If ischemia is severe, widespread neuronal death may result in:
- Persistent vegetative state
- Brain death

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Borderline infarcts occur in watershed areas between……

Anterior cerebral & middle cerebral arteries
Middle & posterior cerebral arteries

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Focal Ischemia

Definition

Causes

Infarction from obstruction of local blood supply (stroke)
Results from arterial stenosis and/or thrombosis, atheroemboli or thromboemboli

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What is selective vulnerability?

Certain brain cells & regions are more susceptible to hypoxia/ischemia than others

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What are the 3 most vulnerable cells of the brain?

(in decreasing order)

Neurons
Oligodendrocytes
Astrocytes

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What are the 3 most vulnerable regions of the brain?

(in decreasing order)

Hippocampus (CA1 sector – Sommer sector)
Lamina 3 & 5 of cerebral cortex (laminar necrosis)
Purkinje cells in cerebellum

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What determines selective vulnerability?

Variable O₂/energy requirements of different neurons & neuronal populations
Glutamate receptor densities
- Glutamate is neurotoxic when present in excess, as occurs in hypoxic/ischemic brain damage

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What do acutely hypoxic/ischemic neurons look like microscopically?

“Red is dead”
Pyknotic cell w/ shrunken & dark nucleus, no nucleolus visible
Red cytoplasm (no Nissl substance visible)

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What is severe global ischemia?

Severe ischemia –> widespread neuronal death irrespective of regional vulnerability
Corresponds to brain death
Non-perfused brain

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What are the clinical signs & symptoms of severe global ischemia?

Persistent vegetative state
- Unconscious, but w/ retention of sleep-wake cycles, primitive orienting responses, brainstem & diencephalon reflexes
Brain death
- Diffuse irreversible cortical injury w/ brainstem injury (absent reflexes & respiratory drive)

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What does severe global ischemia look like….

Grossly?

Microscopically?

Gross
- Swollen brain
- Slit-like ventricles
- Often herniation
Microscopic
- Pallor
- Vacuolation of parenchyma
- Sparse eosinophilic neurons

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What are the 3 most common causes of focal ischemia?

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Thrombosis
Emboli
Lacunar infarcts/slit hemorrhages

How does thrombosis cause focal ischemia?

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Atherosclerosis
Most common sites
- Carotid bifurcation
- Origin of middle cerebral artery
- Origin or end of basilar artery

How do emboli cause focal ischemia?

Cardiac vs. non-cardiac sources?

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Infarcts are most likely hemorrhagic
Cardiac source
- Mural thrombus
  - L atrium or L ventricle
  - Predisposing factors: MI, valve disease, atrial fibrillation, paradoxical embolism
- Endocarditis
  - Bacterial or marantic
Non-cardiac source
- Atheroma (plaques in carotid arteries)
- Fat, neoplasm, air

______ is the most frequent vessel affected by emboli.

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MCA

How do lacunar infarcts/slit hemorrhages cause focal ischemia?

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Hyaline arteriolosclerosis (HTN & DM)
Lacunes
- Small strokes (<1-1.5cm) in subcortical brain structures
- Basal ganglia, internal capsule, thalamus, white matter, pons
- May be hemorrhagic

What are some less common causes of infarction? (6)

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Vasculitis
- Non-infectious causes
- Infectious causes
Arterial dissection of carotid arteries
Coagulation disorders
Microvasculopathy
- Arteriosclerotic Leukoencephalopathy
- CADASIL
Amyloid angiopathy
Drug abuse

What is primary angiitis (vasculitis) of the CNS?

What is it characterized by?

Histology?

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Involves multiple small/medium sized meningeal & parenchymal vessels
Characterized by
- Chronic inflammation
- Fibrinoid necrosis
- Multinucleated giant cells
- Wall destruction
Histology: fibrinoid necrosis of vessel wall w/ inflammation

**Gross Morphology of Infarct ** * Acute * Subacute * Chronic

* **Acute** * Up to 48 hrs * Soft, swollen * Gray-white distinction blurred * **Subacute** * Up to 2-3 wks * Liquefactive necrosis * **Chronic** * Several months * Cavitated, all dead tissue removed

**Microscopic Morphology of Infarct** * Acute * Subacute * Chronic

* **Acute** * 8-12 hrs: red neurons, pallor * Up to 48 hrs: neutrophils (not always) * **Subacute** * 48 hrs to 3 wks * MΦ, necrotic tissue, reactive astrocytes, vascular proliferation * **Chronic** * Several months: cavity w/ glial scar

What does an **acute infarct** look like microscopically?

* Pallor, neutrophils * Preservation of small area around vessel * Red neurons

**Subacute infarct** Histology Imaging

* Days to wks * **Histology** * Liquefactive necrosis * Many MΦ, reactive astrocytes, vascular proliferation, necrotic tissue * **Imaging** * Maximum swelling * Shifting of midline structures * Compression of uninfarcted areas

**Chronic Infarct** Gross/Histology Imaging

* Gross/Histology: cavity w/ fibrillary astrocytic scar * Imaging: large cavity, scar tissue

**Vascular Dementia** Definition Patterns of damage

* Clinical S/S: stepwise progression * Patterns of damage * **Small areas of infarction** – multiple lacunar infarcts * **Diffuse white matter disease** – Binzwanger disease & CADASIL * **Strategic infarcts** – areas important for cognition/memory * Hippocampus, dorsomedial thalamus, frontal cortex, cingulate cortex * Many individuals will have multiple strokes & some changes of Alzheimer’s disease (mixed dementia)

**Cerebral Venous Thrombosis** Definition Causes

* **Hemorrhagic infarcts** * **Superior sagittal sinus or lateral sinuses** * Parasagittal hemorrhagic infarcts * Causes * Infection, injury, neoplasm, surgery * Pregnancy, oral contraceptives, hematologic abnormalities, dehydration, malignancy

What are the 3 major causes of **Intracerebral Hemorrhage**?

* HTN * Vascular Malformations * Amyloid angiopathy

How does **HTN** cause intracerebral hemorrhage?

* Most common cause of primary ICH * Peak occurrence in 60s * Abrupt onset of severe neurologic dysfunction when hematoma is large * _Putamen, thalamus, pons, cerebellum_ * Hyaline arteriolosclerosis

What does **hypertensive** intracerebral hemorrhage look like.... Grossly? Histologically?

* Gross * Extravasation of blood, compression of adjacent brain * Histology * **Hyaline arteriolosclerosis** * Weakens arteriole & predisposes rupture * Charcot-Bouchard microaneurysm

What are the 2 types of **vascular malformations** that cause intracerebral hemorrhage?

* Arteriovenous malformations * Cavernous angioma

**Arteriovenous Malformation** Definition Epidemiology Clinical Presentation

* Most common * M \> F * 10-30 YO * MCA distribution * Can present w/ bleeding * Often presents as: * **Seizures** * **Headaches** * **Focal deficits**

**Arteriovenous Malformation** Gross Histology

* Gross * Tangled network of vessels w/ arteriovenous shunt * Histology * Greatly enlarged blood vessels separated by **gliotic tissue** (evidence of prior hemorrhage)

What is a **cavernous angioma**?

* Cerebellum, pons, white matter * No intervening brain tissue * _Evidence of prior bleeding _

What is **amyloid angiopathy**?

* **Deposition of β-amyloid into the vessel wall** * Elderly, Alzheimer’s disease * Histology: Congo red stain, β-amyloid immunostain

What are 5 common causes of **lobar hemorrhage**?

* Neoplasms * Drug abuse * Vasculitis * Hemorrhagic diathesis * Amyloid angiopathy

What are the 2 common causes of **subarachnoid hemorrhage**?

* Trauma * Aneurysms

What types of _aneurysms_ can cause a subarachnoid hemorrhage? (3)

* Saccular (berry) * Mycotic (fungus) * Fusiform, atherosclerotic

**Saccular "Berry" Aneurysm** Definition Clinical Presentation Histology

* **“The worse headache I’ve ever had!”** * Increased risk w/ HTN, smoking, AVM, etc. * Increasing risk of rupture as size increases * Not present at birth, but _defect in media is congenital_ & aneurysm develops over time * Occurs at branch points, 90% in anterior circulation * Histology * Fibrous wall * Defect in elastic & media (elastic stain)

Cerebrovascular Diseases Flashcards

(43 cards)