Stroke and Cerebrovascular Disease: USMLE Preparation
This module covers Stroke and Cerebrovascular Disease, a critical topic for the USMLE. We will explore the pathophysiology, clinical presentation, diagnosis, and management of various stroke types. Understanding these concepts is vital for clinical decision-making and patient care.
Understanding Stroke: The Basics
A stroke, also known as a cerebrovascular accident (CVA), occurs when blood supply to part of the brain is interrupted or reduced, preventing brain tissue from getting oxygen and nutrients. Brain cells begin to die in minutes.
Types of Stroke
| Stroke Type | Description | Common Causes | Key Features |
|---|---|---|---|
| Ischemic Stroke | Caused by a blockage in an artery supplying blood to the brain. | Blood clots (thrombosis or embolism), atherosclerosis. | Sudden onset of focal neurological deficits. |
| Hemorrhagic Stroke | Caused by bleeding into or around the brain. | Hypertension, ruptured aneurysms, arteriovenous malformations (AVMs). | Sudden, severe headache (thunderclap), nausea, vomiting, altered consciousness. |
| Transient Ischemic Attack (TIA) | Temporary blockage of blood flow to the brain, causing stroke-like symptoms that resolve within minutes to hours. | Similar to ischemic stroke, but temporary. | Neurological deficits that resolve completely, often a warning sign for future stroke. |
Ischemic Stroke: Pathophysiology and Etiology
Ischemic strokes account for about 87% of all strokes. They are primarily caused by either a thrombus (a blood clot that forms in an artery supplying the brain) or an embolus (a blood clot or other debris that travels from another part of the body and lodges in a brain artery). Atherosclerosis, the buildup of plaque in arteries, is a major underlying cause.
Hemorrhagic Stroke: Pathophysiology and Etiology
Hemorrhagic strokes occur when a blood vessel in the brain ruptures, leading to bleeding. This can be intraparenchymal (within the brain tissue) or subarachnoid (in the space between the brain and the membranes that cover it). Uncontrolled hypertension is the most common cause of intraparenchymal hemorrhage, while ruptured aneurysms are a frequent cause of subarachnoid hemorrhage.
Clinical Presentation and Diagnosis
The symptoms of stroke depend on the area of the brain affected and the extent of damage. Common symptoms include sudden numbness or weakness, confusion, trouble speaking or understanding speech, vision problems, dizziness, and severe headache. The FAST acronym (Face drooping, Arm weakness, Speech difficulty, Time to call emergency services) is a useful mnemonic for recognizing stroke symptoms.
The diagnosis of stroke relies on a combination of clinical assessment and neuroimaging. Initial evaluation typically involves a rapid neurological exam to assess for focal deficits. Non-contrast head CT is the first-line imaging modality to differentiate between ischemic and hemorrhagic stroke. MRI, CT angiography (CTA), and MR angiography (MRA) provide more detailed information about blood flow and vessel integrity.
Text-based content
Library pages focus on text content
Diagnostic Tools
Key diagnostic tools include:
- Non-contrast Head CT: Essential for ruling out hemorrhage quickly.
- CT Angiography (CTA): Visualizes blood vessels to identify blockages or aneurysms.
- MRI/MRA: Provides detailed brain imaging and vascular assessment, often more sensitive for early ischemic changes.
- Cerebral Angiography: Invasive procedure to visualize blood vessels, used in specific cases.
Management of Stroke
Management strategies vary based on stroke type and time since symptom onset. For ischemic stroke, reperfusion therapies like intravenous thrombolysis (tPA) and mechanical thrombectomy are crucial for restoring blood flow. For hemorrhagic stroke, management focuses on controlling blood pressure, reversing anticoagulation if applicable, and surgical intervention to evacuate hematomas or repair vascular abnormalities.
For ischemic stroke, the 'golden hour' is critical. Intravenous thrombolysis with alteplase (tPA) is most effective when administered within 4.5 hours of symptom onset. Mechanical thrombectomy can be considered up to 24 hours in select patients.
Rehabilitation and Secondary Prevention
Post-stroke, rehabilitation is vital for recovery. This includes physical therapy, occupational therapy, and speech therapy to regain lost function. Secondary prevention aims to reduce the risk of future strokes through lifestyle modifications, medication (e.g., antiplatelets, statins), and management of underlying risk factors like hypertension, diabetes, and hyperlipidemia.
Ischemic stroke.
Non-contrast head CT.
FAST (Face drooping, Arm weakness, Speech difficulty, Time to call emergency services).
Learning Resources
Provides a comprehensive overview of stroke symptoms, causes, and risk factors from a reputable medical institution.
Offers detailed information on stroke types, prevention, treatment, and recovery from a leading authority on stroke.
An in-depth clinical resource for healthcare professionals, providing detailed pathophysiology, diagnosis, and management guidelines for stroke.
A review article from the New England Journal of Medicine discussing the latest advancements in stroke research and treatment.
A clear and concise video explaining the basics of stroke, its causes, and effects.
A detailed guide on the medical treatment and management strategies for various types of cerebrovascular accidents.
Information about a national network dedicated to advancing stroke research and improving stroke care.
Provides statistics, risk factors, and public health information related to stroke from a government health agency.
Focuses on the radiological diagnosis of ischemic stroke, including imaging findings and interpretation.
Access to international guidelines for stroke prevention, treatment, and rehabilitation.