Welcome to Module 1

In this module we will be talking about the etiology, or causes of stroke, and also the common risk factors for stroke. The various causes for stroke are split into respective subtypes based on these causes. These causes generally cause a lack of blood flow to the brain due to a narrowing of the artery or a blockage via a clot.¹

Below are a list of the most common etiologies of ischemic stroke:

Large Artery Atherosclerosis (LAA)

Atherosclerosis is defined by the formation of fibrofatty plaques in arteries, causing narrowing (stenosis) and reduction in blood flow (ischemia). Eventually, it leads to tissue damage and necrosis. ² In large artery atherosclerosis, there is significant stenosis and complete occlusion of major/branch cerebral arteries.¹

Diagnosis:

• Clinical features: cortical impairment and dysfunction at the cerebellum and brainstem, history of intermittent claudication and transient ischemic attack in affected areas.¹

• Infarctions larger than 1.5 cm in diameter on computed tomography (CT) or magnetic resonance imaging (MRI), especially those that originated from the cortex, cerebellum, brainstem, or subcortical regions.¹

Risk Factors:

• Age, sex, family history, ethnicity, obesity, stress² 

Cardioembolism 

Cardioembolism is defined by an clot that was formed in the heart and pumped into the brain's circulation. This can cause a blockage of a brain blood vessel and damages brain tissues, resulting in cardioembolic stroke.3 Cardioembolic strokes account for 14-30% of ischemic strokes.4  

Diagnosis4:

• CT scan showing infarct within brain arteries can be suggestive

  • MRI can increase suspicion by showing non-apparent damages

Risk Factors3, 4 :

• Atrial fibrillation 

  • Irregular and rapid heart rhythm

• Recent myocardial infarction

  • Stoppage of blood flow to a portion of the heart

• Mechanical prosthetic valve

• Dilated Myocardiopathy

  • Chambers of the thin, stretches, and enlarge. Impairing blood flow.

• Mitral rheumatic stenosis

  • Narrowing of heart valve due to past fever.

Small Vessel Occlusions

Lacunar infarcts, or small vessel occlusions, occur when small vessels in the brain become occluded or are narrowed, blocking blood flow thus causing ischemia.¹

Diagnosis:

• Patient does not present signs of cerebral cortical dysfunction such as seizures or cognitive impairment¹

• Patient has no evidence of an embolism¹

• Patient's major extracranial arteries should not have stenosis that is greater than 50% at the same vascular site. ¹

Risk Factors:

• The history of hypertension or diabetes provides strong evidence that supports the diagnosis. The patient with a lacunar infarct is usually diagnosed with a relevant lacunar syndrome such as pure motor hemiparesis or pure sensory syndrome. ¹

Strokes of Determined Etiology 

Rarer causes of stroke fall under this category, such as nonatherosclerotic vasculopathies, hypercoagulable states, or hematological disorders. These can be diagnosed with tests on blood work or an arteriography combined with imaging such as CT scans or MRI. ¹

Strokes of Undetermined Etiology

Cases when the specific etiology (cause) of the stroke cannot be diagnosed after a broad range of diagnostic tests. This category includes the cases when the cause of ischemic stroke cannot be confirmed. ¹

Review Questions

ANSWER KEY

1. A

2. C

3. D