Definition
Ischemic Stroke Overview
- Defined by the sudden loss of blood circulation to a brain region, resulting in neurological deficits.
- Typically caused by thrombotic or embolic occlusion of a cerebral artery.
- Ischemic strokes are more common than hemorrhagic strokes.
ICD-10-CM Classification
- Categorised as “cerebral infarction” under code I63.
- Includes occlusion and stenosis of cerebral and precerebral arteries.
World Health Organization Definition
- Stroke is described as a syndrome involving rapidly developing focal (or global) cerebral dysfunction.
- Symptoms last more than 24 hours or lead to death.
- Vascular origin is the primary cause.
TOAST Classification of Ischemic Stroke
Large artery atherosclerosis
- Thrombosis or embolism due to atherosclerotic changes in large arteries.
Cardioembolism
- Emboli originating in the heart, often associated with atrial fibrillation or cardiac anomalies.
Small vessel occlusion (lacunar stroke)
- Thrombosis in small penetrating arteries, commonly linked to hypertension or diabetes.
Stroke of other determined aetiology
- Rare causes such as arterial dissections, vasculitis, or hypercoagulable states.
Stroke of undetermined aetiology
- Cryptogenic strokes or those with multiple potential causes.
Aetiology
Risk Factors
Non-modifiable Risk Factors
- Age: Increased risk with advancing age.
- Sex and Race: Variations in risk based on demographic factors.
- Genetic Factors: Family history of stroke or transient ischemic attack (TIA).
- Migraine with Aura: Particularly in younger women, significantly increases stroke risk.
Modifiable Risk Factors
- Hypertension: The most critical risk factor.
- Diabetes Mellitus: Promotes vascular disease and thrombosis.
- Cardiac Disease: Includes atrial fibrillation, heart failure, and valvular disorders.
- Hyperlipidemia: Increases atherosclerotic plaque formation.
- Lifestyle Factors: Smoking, excessive alcohol use, sedentary lifestyle, and obesity.
- Hormonal Factors: Oral contraceptives and postmenopausal hormone therapy.
- Sickle Cell Disease: Increases susceptibility to vascular stenosis and ischemia.
Pathophysiology
Genetic and Inflammatory Mechanisms
Atherosclerosis
- Driven by chronic inflammation and endothelial injury.
- Risk factors include oxidised low-density lipoprotein (LDL) cholesterol and smoking.
Genetic Mutations
- Mutations in F2, F5, and other genes (e.g., NOS3, ALOX5AP) increase susceptibility.
- Conditions like CADASIL and amyloid angiopathy are associated with genetic variants affecting vascular integrity.
Hyperhomocysteinemia
- Caused by mutations in the MTHFR gene or CBS deficiency.
- Elevated homocysteine levels are linked to vascular damage.
Mechanisms of Ischemic Stroke
General Pathogenesis
- Ischemic stroke results from events that limit or stop cerebral blood flow, such as:
- Thrombotic embolism from extracranial or intracranial sources.
- Thrombosis in situ within an affected artery.
- Relative hypoperfusion due to systemic conditions like hypotension or heart failure.
- Neurons cease functioning as blood flow decreases, with irreversible neuronal damage occurring below 18 mL/100 g of tissue/min and cell death at rates below 10 mL/100 g of tissue/min.
Large Artery Occlusion
- Often results from embolisation of atherosclerotic debris from the carotid arteries or cardiac sources.
- Plaque ulceration and in situ thrombosis are additional contributors.
- Most commonly affects the middle cerebral artery (MCA) territory.
Lacunar Strokes
- Represent 13–20% of ischemic strokes, caused by occlusion of small penetrating arteries.
- Commonly associated with chronic hypertension, leading to lipohyalinosis, microatheroma, or fibrinoid necrosis.
Cardioembolic Strokes
- Account for up to 20% of ischemic strokes.
- Sources include valvular thrombi (e.g., mitral stenosis), mural thrombi, or atrial myxoma.
- Associated with conditions like atrial fibrillation and myocardial infarction.
Watershed Infarcts
- Occur in distal arterial territories due to embolic phenomena or severe hypoperfusion.
- Commonly found in border zones between major cerebral arteries.
Epidemiology
Global and National Burden
Global Statistics
- Stroke is a leading cause of disability and a significant contributor to global mortality.
- Annually, 15 million people suffer from stroke worldwide, with 5 million deaths and 5 million left permanently disabled.
United States
- Stroke ranks as the fifth leading cause of death and a major cause of long-term disability in the U.S.
- Approximately 795,000 strokes occur annually, with 610,000 being first-time events and 185,000 recurrent strokes.
- Ischemic strokes account for 87% of all strokes.
- Financial burden: Between 2018 and 2019, stroke costs totaled approximately $56.5 billion in healthcare, medication, and lost productivity.
United Kingdom
- More than 100,000 strokes occur annually, leading to 38,000 deaths.
- Stroke is a significant cause of disability and mortality, with increasing prevalence among individuals aged over 55.
Race, Sex, and Age Disparities
Race and Ethnicity
- In the U.S., African Americans have nearly double the risk of first stroke compared to White populations, with the highest mortality rates observed among non-Hispanic Black and Pacific Islander adults.
- Hispanic populations have a lower overall incidence but experience lacunar strokes more frequently and at younger ages.
- Indigenous populations in high-income countries face a higher stroke incidence compared to non-Indigenous groups.
Sex Differences
- Men have a higher stroke incidence compared to women; however, women experience higher mortality rates following stroke.
Age-Related Trends
- Stroke predominantly affects individuals aged over 65, with 75% of cases occurring in this demographic.
- However, one-third of strokes occur in individuals under 65 years of age.
- Incidence in younger adults is reportedly increasing, particularly in low- and middle-income countries.
Regional and Socioeconomic Patterns
Global Patterns
- Stroke burden disproportionately affects low- and middle-income countries, accounting for 86% of deaths and 89% of disability-adjusted life-years (DALYs).
- Highest risks for stroke are observed in East Asia, Central Europe, and Eastern Europe, while the lowest risks are in eastern sub-Saharan Africa.
High-Income Countries
- Stroke incidence and mortality rates have declined over recent decades due to advances in prevention and care.
- Socioeconomic factors, such as lower educational attainment, are linked to higher stroke prevalence.
Stroke Subtypes in Ischemic Cases
- Ischemic strokes are classified by pathophysiology:
- Extracranial atherosclerosis: 10%.
- Intracranial atherosclerosis: 10%.
- Cardioembolic strokes: 25%.
- Lacunar infarctions (small vessel disease): 15%.
- Cryptogenic strokes (indeterminate aetiology): 30%.
- Other defined causes: 10%.
History
Focused Medical History
Key Risk Factors:
- Hypertension, diabetes mellitus, tobacco use, high cholesterol.
- History of coronary artery disease, atrial fibrillation, or coronary artery bypass surgery.
In Younger Patients
- History of recent trauma, coagulopathies, illicit drug use (e.g., cocaine), migraines, and oral contraceptive use.
Presentation of Symptoms
- Sudden onset of acute neurologic deficits or altered level of consciousness.
- Common stroke symptoms include:
- Hemiparesis, hemisensory deficits, facial droop, dysarthria.
- Monocular or binocular visual loss, visual field deficits, diplopia.
- Ataxia, vertigo, aphasia, and sudden decrease in consciousness.
- Symptoms may present alone or in combination.
Establishing Time of Symptom Onset
- Critical for considering fibrinolytic therapy.
- Time of onset is defined as the last known normal time or when the patient was last without symptoms.
- Input from family, coworkers, or bystanders may assist, especially in "wake-up" strokes.
Neurological
Motor Deficits
- Hemiparesis or monoparesis typically involving the face, arm, or leg.
- Quadriparesis is rare and suggests a more severe condition.
- Lacunar syndromes like pure motor hemiparesis or ataxic hemiparesis may occur with small vessel occlusion.
Language Impairments
- Dysphasia indicates dominant hemispheric ischemia.
- Dysarthria often accompanies facial weakness or brainstem dysfunction.
Ataxia
- Suggests cerebellar ischemia or its connections.
- More common in posterior circulation strokes, often affecting fine motor coordination and gait.
Visual Disturbances
- Amaurosis fugax may indicate cervical carotid stenosis.
- Homonymous hemianopia involves vision loss in the same visual field of both eyes.
- Diplopia can occur in posterior circulation ischemia.
Sensory Loss
- Unilateral sensory deficits may involve primary modalities or fine sensory processing.
Physical Examination
Examination
Objectives of the Physical Examination
- Detect extracranial causes of stroke symptoms.
- Differentiate stroke from stroke mimics.
- Document the degree of neurologic deficit for future comparison.
- Localise the lesion.
- Identify comorbidities and conditions influencing treatment, such as recent surgery, trauma, active bleeding, or infection.
General Physical Examination
Vital Signs
- May indicate clinical deterioration or assist in narrowing the differential diagnosis.
- Hypertension is common in stroke patients but often decreases spontaneously over time.
Head and Neck Examination
- Inspect for trauma, infection, or meningeal irritation.
- Auscultation for carotid bruits may reveal carotid disease.
Cardiac and Peripheral Vascular Examination
- Look for arrhythmias like atrial fibrillation, murmurs, or gallops, which are associated with embolic strokes.
- Unequal pulses or blood pressure differences in extremities may suggest aortic dissection.
Neurological Examination
Purpose
- Confirm the presence of a stroke syndrome.
- Establish a neurological baseline using tools like the NIH Stroke Scale (NIHSS).
- Assess stroke severity for prognosis and therapeutic decisions.
Key Components
Cranial Nerve Examination
- Assesses deficits that may help localise the lesion.
Motor and Sensory Function
- Detect hemiparesis, monoparesis, or sensory loss.
Cerebellar Function
- Evaluate for ataxia, which may indicate cerebellar involvement or posterior circulation ischemia.
Gait and Coordination
- Assess for abnormalities linked to stroke.
Language and Mental Status
- Identify expressive or receptive aphasia and cognitive impairments.
Consciousness
- Establish level of alertness and responsiveness.
National Institutes of Health Stroke Scale (NIHSS)
- A 42-point scale used to quantify stroke severity and localise the lesion.
- Focuses on six major areas:
- Level of consciousness.
- Visual function.
- Motor function.
- Sensory function and neglect.
- Cerebellar function.
- Language abilities.
- Scores correlate with outcomes:
- <5: Minor stroke.
- >10: High likelihood of proximal vessel occlusion.
Stroke Syndromes and Vascular Localisation
Middle Cerebral Artery (MCA)
- Symptoms: Contralateral hemiparesis (worse in arm and face), hemianopsia, aphasia (dominant hemisphere), neglect (non-dominant hemisphere).
Anterior Cerebral Artery (ACA)
- Symptoms: Leg weakness greater than arm, gait apraxia, impaired judgment, urinary incontinence.
Posterior Cerebral Artery (PCA)
- Symptoms: Visual disturbances (homonymous hemianopia), cortical blindness, memory impairment.
Vertebrobasilar Artery
- Symptoms: Cranial nerve deficits, ataxia, vertigo, dysarthria, and ipsilateral cranial nerve/contralateral motor deficits.
Lacunar Strokes
- Symptoms: Pure motor or sensory deficits without cortical signs (e.g., aphasia, neglect).
Additional Clinical Observations
Visual Disturbances
- Amaurosis fugax or transient monocular blindness may indicate carotid stenosis.
- Homonymous hemianopia suggests cortical involvement.
Dysarthria
- May accompany brainstem or cerebellar strokes.
Ataxia
- Points to posterior circulation or cerebellar involvement.
Vertigo
- Common in posterior circulation ischemia, often accompanied by nystagmus.
Nausea and Vomiting
- May reflect posterior circulation involvement or increased intracranial pressure.
Seizures
- More frequently associated with hemorrhagic stroke.
Investigations
Primary and Essential Investigations
Non-Contrast CT (NCCT) Head
- Purpose: First-line imaging to differentiate ischemic from hemorrhagic stroke.
- Key Points:
- Must be performed within 1 hour of arrival at the hospital.
- Hypoattenuation and loss of gray-white matter differentiation are early ischemic signs.
- Hyperattenuation indicates clot presence.
- Practical Considerations:
- A normal CT does not exclude stroke, especially within the first few hours.
- Requires immediate interpretation by trained personnel for critical treatment decisions.
Serum Glucose
- Purpose: Exclude hypoglycemia, a stroke mimic, and assess for hyperglycemia, which is associated with worse outcomes in ischemic stroke.
- Practical Considerations: Always check prior to administering thrombolytic therapy.
Electrocardiogram (ECG)
- Purpose: Identify arrhythmias like atrial fibrillation or ischemia that might suggest a cardioembolic source.
- Key Points:
- Prolonged monitoring, including implantable loop recorders, may be needed in cryptogenic strokes.
Serum Electrolytes, Urea, and Creatinine
- Purpose: Evaluate for electrolyte imbalances and renal dysfunction, which can mimic stroke or impact treatment.
Prothrombin Time (PT), Partial Thromboplastin Time (PTT), and INR
- Purpose: Rule out coagulopathies and assess anticoagulation status.
- Practical Considerations: Do not delay thrombolysis unless anticoagulation history is known.
Full Blood Count (FBC)
- Purpose: Identify anemia or thrombocytopenia that could influence treatment options.
Cardiac Enzymes
- Purpose: Evaluate for myocardial infarction as a concurrent or contributing condition.
Advanced Imaging Techniques
MRI with Diffusion-Weighted Imaging (DWI)
- Purpose:
- More sensitive than NCCT in detecting early ischemic changes and cerebral edema.
- Provides greater anatomical detail and detects infarction earlier.
- Practical Considerations:
- Contraindicated in patients with certain implants or pacemakers.
- Limited availability in emergency settings compared to CT.
CT Angiography (CTA)
- Purpose:
- Identify large vessel occlusions and assess suitability for thrombectomy.
- Practical Considerations:
- Can be performed alongside NCCT without delaying thrombolysis.
Perfusion Imaging (CT or MRI)
- Purpose: Detect areas of salvageable brain tissue in delayed presentations or when considering thrombectomy (6–24 hours post-onset).
- Key Points:
- Highlights mismatch between ischemic core and penumbra.
Carotid Ultrasound
- Purpose:
- Identify critical stenosis or occlusion in patients considered for carotid intervention.
- Practical Considerations:
- Often used for stroke patients evaluated for endarterectomy or stenting.
Echocardiography (TTE/TEE)
- Purpose:
- Detect potential cardioaortic embolic sources like atrial thrombi, vegetations, or patent foramen ovale.
Laboratory Studies and Other Investigations
Toxicology Screen
- Purpose: Identify substance use (e.g., cocaine) mimicking stroke or causing ischemia/hemorrhage.
Cardiac Biomarkers
- Purpose: Assess for concurrent cardiac pathology.
Arterial Blood Gas (ABG):
- Purpose: Diagnose acid-base disturbances in suspected hypoxemic patients.
Coagulation Studies
- Purpose: Identify coagulopathies influencing stroke pathophysiology or treatment.
Practical Workflow and Tips
Immediate Actions
- Conduct NCCT within 1 hour of arrival and follow with CTA for thrombectomy candidates.
- Monitor glucose levels and assess coagulation before thrombolysis.
Communication
- Radiologist collaboration is crucial for timely imaging interpretation.
- Engage cardiology services for detailed cardiac evaluations in suspected embolic strokes.
Differential Diagnoses
Transient Ischemic Attack (TIA)
- Signs and Symptoms:
- Sudden onset of focal neurological symptoms resolving within minutes to hours, usually within 24 hours.
- Complete recovery is typical, with no residual deficits.
- Investigations:
- Brain imaging (CT or MRI) may be normal or reveal evidence of previous infarcts.
Hypertensive Encephalopathy
- Signs and Symptoms:
- Severe hypertension above baseline, accompanied by headache, confusion, visual changes, or reduced consciousness.
- May present with signs of increased intracranial pressure.
- Investigations:
- Brain imaging (CT or MRI) may show cerebral edema.
Intracerebral Hemorrhage
- Signs and Symptoms:
- Presents with sudden headache, vomiting, reduced consciousness, and focal neurological deficits.
- Increased intracranial pressure may be evident.
- Investigations:
- Brain imaging (CT or MRI) demonstrates hyperattenuation consistent with hemorrhage.
Hypoglycemia
- Signs and Symptoms:
- Often associated with diabetes and the use of insulin or hypoglycemic agents.
- Symptoms include confusion, altered consciousness, or focal neurological deficits mimicking stroke.
- Investigations:
- Low serum glucose levels during symptom onset confirm diagnosis.
Complicated Migraine
- Signs and Symptoms:
- History of similar events with preceding aura and positive symptoms, such as visual or sensory disturbances.
- Negative symptoms, such as weakness or numbness, are more typical of stroke.
- Investigations:
- MRI excludes infarction.
Seizure and Postictal Deficits
- Signs and Symptoms:
- History of seizures or witnessed convulsions followed by transient neurological deficits.
- Wrong-way eye deviation (gaze away from the side of the lesion) may occur.
- Investigations:
- Electroencephalogram confirms seizure activity.
- MRI excludes infarction.
Functional Neurological Disorder
Signs and Symptoms:
- Neurological symptoms inconsistent with vascular territories.
- May lack cranial nerve deficits or show multiple inconsistent signs.
- Psychological comorbidities like anxiety and depression are common.
- Investigations:
- MRI is normal, with no evidence of infarction.
Brain Tumor
- Signs and Symptoms:
- Gradual onset of neurological symptoms.
- May present with a history of known malignancy or systemic cancer.
- Investigations:
- CT or MRI shows space-occupying lesions.
Wernicke’s Encephalopathy
- Signs and Symptoms:
- History of alcohol abuse or malnutrition.
- Presents with confusion, ataxia, and ophthalmoplegia.
- Investigations:
- Low blood thiamine levels.
- Improvement with thiamine administration supports the diagnosis.
Ingestion of Toxic Substances
- Signs and Symptoms:
- History of alcohol or drug use, with symptoms mimicking stroke.
- Investigations:
- Positive toxicology screen for alcohol or drugs.
Management
Urgent Initial Management
Stroke as an Emergency
- "Time is brain" underscores the need for rapid intervention to minimise neurological damage.
- Early reperfusion strategies, including intravenous thrombolysis and mechanical thrombectomy, improve outcomes when initiated within 4.5 hours of symptom onset.
Stabilisation
- Airway and Breathing:
- Endotracheal intubation is recommended for patients with a Glasgow Coma Scale (GCS) score ≤8 or those unable to protect their airway.
- Supplemental oxygen is indicated only when oxygen saturation drops below 93%; higher saturation targets (>96%) may increase mortality risk.
-
Circulation:
- Blood pressure management is critical but should only be actively reduced in hypertensive emergencies, such as hypertensive encephalopathy, cardiac failure, or aortic dissection.
Hospital Admission and Monitoring
- All suspected stroke patients should be admitted directly to a hyperacute stroke unit within 4 hours of hospital arrival to enable early thrombolysis and prevent complications.
- Monitor for elevated intracranial pressure (ICP), presenting as worsening consciousness, severe headache, or abrupt hypertension. Prompt imaging and neurosurgical referral are required for suspected ICP.
Reperfusion Therapy
Intravenous Thrombolysis
- Administer alteplase within 4.5 hours of symptom onset for eligible patients after excluding contraindications (e.g., intracranial hemorrhage or coagulopathy).
- Thrombolysis with tenecteplase is a potential alternative (off-label in the UK).
- Do not delay thrombolysis awaiting additional tests unless contraindications are suspected.
Mechanical Thrombectomy
- Perform within 6 hours of symptom onset for proximal anterior circulation occlusions.
- For wake-up strokes or those presenting 6–24 hours after symptom onset, thrombectomy is indicated if imaging demonstrates salvageable brain tissue, such as perfusion mismatch.
- Consider thrombectomy alone in patients ineligible for thrombolysis, such as those on anticoagulants or with recent surgery.
Secondary and Supportive Care
Antiplatelet Therapy
- Start aspirin within 24 hours of excluding intracerebral hemorrhage, delaying its use if thrombolysis was performed. A repeat CT scan is required to rule out post-thrombolysis bleeding.
- Dual antiplatelet therapy (aspirin and clopidogrel or ticagrelor) is recommended for 21–30 days in minor strokes (NIHSS ≤3), transitioning to single therapy for long-term prevention.
Blood Pressure Management
- For thrombolysis candidates, target a blood pressure of ≤185/110 mmHg before treatment.
- In non-thrombolysis patients, reduce blood pressure cautiously (>220/120 mmHg) to avoid abrupt declines.
Glycemic Control
- Maintain blood glucose between 4–11 mmol/L to prevent complications.
Statins
- Initiate high-intensity statin therapy 48 hours after stroke if atherosclerosis is confirmed.
- Adjust or continue existing statin regimens as needed.
Temperature Regulation
- Treat fever with antipyretics. Avoid therapeutic hypothermia as it does not reduce secondary brain damage.
Swallowing and Nutrition
- Assess swallowing before oral intake. Provide tube feeding for patients unable to swallow adequately and address malnutrition when present.
Neurosurgical Interventions
Decompressive Hemicraniectomy
- Consider for large middle cerebral artery infarcts meeting imaging and clinical criteria, such as decreased consciousness (GCS ≤8) or infarcts involving >50% of the MCA territory.
- Perform within 48 hours of symptom onset to reduce mortality and prevent herniation.
Preventing and Managing Complications
Intracranial Pressure Monitoring:
- Monitor for signs of ICP elevation, including altered consciousness and headache.
- Surgical options include ventriculostomy for cerebellar infarctions or decompressive craniectomy for malignant MCA syndrome.
Seizures:
- Treat with anticonvulsants such as levetiracetam or sodium valproate. Consult specialists for uncontrolled seizures or status epilepticus.
Deep Vein Thrombosis (DVT) Prevention:
- Use intermittent pneumatic compression devices. Low-molecular-weight heparin is an option if contraindications to compression exist.
Rehabilitation and Long-Term Management
Early Mobilisation
- Begin light mobilisation (e.g., sitting or standing) 24–48 hours after symptom onset if clinically appropriate.
- Avoid high-intensity mobilisation in the first 24 hours.
Long-Term Anticoagulation
- Start anticoagulation in patients with atrial fibrillation or cardioembolic stroke once bleeding risks are addressed.
Prognosis
Overview
- Prognosis is influenced by stroke type, severity, pre-existing comorbidities, treatment response, and post-stroke complications.
- Clinical tools like the National Institutes of Health Stroke Scale (NIHSS), modified Rankin Scale (mRS), and imaging studies are key for predicting outcomes.
Mortality and Survival Rates
- Approximately 19% of patients with ischemic stroke die within 30 days, and 77% survive at one year.
- Cardiogenic emboli have the highest one-month mortality among stroke subtypes.
Predictive Models
- NIHSS: High scores indicate greater early mortality and poorer outcomes.
- CT Findings: Early evidence of infarction correlates with worse outcomes and higher hemorrhagic transformation risk.
- Mortality Prediction Score:
- Developed using data from Austrian stroke registries.
- Factors include age, NIHSS score, pre-stroke functional status, diabetes, heart disease, and stroke subtype.
- Scores ≥10 predict a 35% mortality risk within seven days.
Functional Outcomes
- Recovery varies:
- Some patients achieve full or near-full recovery with timely and intensive rehabilitation.
- Moderate to severe strokes often result in persistent motor, cognitive, or sensory impairments.
- Stroke remains a leading cause of long-term global disability.
Impact of Acute Interventions
- Intravenous Thrombolysis:
- Alteplase improves functional outcomes when given within 4.5 hours of symptom onset.
- While it increases intracerebral hemorrhage risk, long-term mortality or dependency rates are not significantly affected.
- Tenecteplase:
- Non-inferior to alteplase for achieving functional independence (90-day mRS 0–1).
- May be superior for moderate disability outcomes (90-day mRS 0–2).
- Not advised for wake-up strokes without advanced imaging confirmation.
Complications
Common Complications
- Include aspiration pneumonia, depression, and deep vein thrombosis, which contribute to poorer outcomes.
Hyperglycemia
- Associated with larger infarct sizes and worse functional recovery.
Hemorrhagic Transformation:
- Occurs in 5% of ischemic strokes without fibrinolysis.
- Can range from small petechial hemorrhages to significant hematomas.
Rehabilitation and Recovery
- Physiotherapy improves outcomes, even when initiated late.
- Specialised stroke units with early, intensive rehabilitation enhance recovery and reduce disability.
Global Burden
- Stroke accounted for 6.5 million deaths globally in 2019 and remains a major cause of long-term disability.
- Early interventions like thrombolysis and specialised stroke care are proven to improve outcomes.
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