How is a stroke classified and what are the management strategies for each type?

Stroke Classification and Management

Stroke is fundamentally classified into two major categories—ischemic (85% of cases) and hemorrhagic (15% of cases)—with ischemic strokes further subdivided by mechanism into large-artery atherosclerosis, cardioembolism, small-vessel (lacunar) disease, other determined causes, and undetermined etiology, each requiring distinct management approaches. 1, 2

Primary Classification: Ischemic vs Hemorrhagic

Initial Differentiation

• Brain imaging with CT or MRI is mandatory to distinguish between ischemic and hemorrhagic stroke, as this distinction is critical for treatment decisions 3
• CT should be completed within 25 minutes of emergency department arrival, with interpretation within 45 minutes for patients who are potential thrombolytic candidates 3
• MRI with diffusion-weighted imaging (DWI) is preferred when available, as it can detect infarction in approximately 40% of patients even with transient symptoms 4

Hemorrhagic Stroke Subtypes

Hemorrhagic strokes must be separated into two distinct categories 3:

Intracerebral Hemorrhage (ICH):

• Classified by location: deep (basal ganglia), lobar, brainstem, cerebellar, primary intraventricular, single or multiple 3
• Deep hemorrhages typically result from hypertensive arteriopathy, while lobar hemorrhages are mainly caused by cerebral amyloid angiopathy 2
• Severity should be assessed using Glasgow Coma Scale (minimum requirement) or ICH score/FUNC score (preferred) 3
• ICH volume measured by ABC/2 method, with documentation of intraventricular extension and "spot sign" presence 3

Subarachnoid Hemorrhage (SAH):

• Classified etiologically as aneurysmal rupture (aSAH—berry or fusiform) or non-aneurysmal subtypes (intracranial dissection, perimesencephalic, cortical SAH) 3
• Severity graded using Hunt and Hess scale or World Federation of Neurosurgical Societies (WFNS) scale 3
• Initial hemorrhage volume classified via Fisher or Hijdra scales 3

Ischemic Stroke Classification

Mechanistic Subtypes

The American Heart Association classification system divides ischemic strokes into five categories 1:

1. Large-Artery Atherosclerosis:

• Significant stenosis (>50%) or occlusion of major brain artery or branch cortical artery due to atherosclerosis 1, 4
• Typically presents with cortical infarcts in the distribution of a large cerebral artery 1
• Often preceded by TIAs in the same arterial distribution 1
• Vascular imaging (CTA, MRA, or duplex ultrasound) is necessary to identify significant stenosis 4

2. Cardioembolic Stroke:

• Results from emboli originating from the heart or aorta 1
• Presents as cortical or large subcortical infarctions with identifiable high-risk cardiac source 1
• Associated with the highest mortality rate among ischemic stroke subtypes 1
• Requires cardiac evaluation including echocardiography and extended cardiac rhythm monitoring to identify sources such as atrial fibrillation 4
• DWI on MRI shows scattered emboli in multiple vascular territories 4

3. Small-Artery (Lacunar) Stroke:

• Small infarcts (<1.5 cm diameter) in deep brain structures or brainstem 1, 5
• Caused by occlusive arteriopathy of small penetrating arteries 1
• Typically associated with diabetes or hypertension rather than atherosclerosis 1
• Best prognosis among ischemic stroke subtypes, with 85% survival at 2 years 5

4. Stroke of Other Determined Cause:

• Includes dissection, hypercoagulable states, sickle cell disease, Fabry disease 3
• These patients should be categorized by their specific etiologies, not combined into a generic "other" category 3

5. Stroke of Undetermined Cause:

• Approximately 25% of ischemic strokes remain of uncertain etiology despite adequate investigation 4
• TOAST classification is the minimum acceptable standard, though more stringent systems like the Causative Classification System (CCS) are preferred for prospective studies 3

Distinguishing Thrombotic from Embolic Mechanisms

Imaging patterns are crucial for differentiation 4:

• Embolic pattern: Multiple, scattered lesions in different vascular territories on DWI 4
• Thrombotic pattern: Single territory involvement, often with watershed distribution suggesting hypoperfusion from carotid disease 4
• Absence of significant stenosis at the site of occlusion suggests embolic etiology 4

Severity Classification

Ischemic Stroke Severity

• National Institutes of Health Stroke Scale (NIHSS) is the recommended standardized assessment tool 3
• Hospitals must provide necessary resources to implement stroke rating scales 3
• Initial severity assessment allows determination of outcomes and enables adjustment for severity in treatment decisions 3

Functional Classification

• Modified Rankin Scale (mRS) at 30 days is the standard outcome measure 5:
  • Non-disabling infarct: mRS <3 (significant functional independence) 5
  • Disabling infarct: mRS ≥3 (most widely accepted definition in acute stroke trials) 5
• Functional classification is more relevant for predicting morbidity and mortality than anatomical size 5

Management Strategies by Stroke Type

Ischemic Stroke Management

Acute Phase:

• For patients presenting within 4.5 hours of last known well, determine eligibility for intravenous recombinant tissue plasminogen activator (rtPA) 6
• Specialized MRI studies can extend the treatment window to 9 hours for selected patients 6
• Patients with large vessel occlusions presenting within 24 hours should undergo cerebrovascular imaging to assess benefits of endovascular interventions 6

Diagnostic Workup:

• Limited hematologic, coagulation, and biochemistry tests during initial emergency evaluation 3
• ECG is mandatory due to high incidence of heart disease in stroke patients 3
• Chest x-ray is NOT routinely needed for most stroke patients 3
• Extended cardiac monitoring beyond 24 hours significantly increases detection of occult atrial fibrillation in cryptogenic strokes 4

Subtype-Specific Considerations:

• Large-artery atherosclerosis requires comprehensive vascular imaging of intracranial and cervical arteries 4
• Cardioembolic strokes necessitate thorough cardiac evaluation including echocardiography 4
• Small-vessel disease management focuses on blood pressure control and diabetes management 1

Hemorrhagic Stroke Management

ICH Management:

• Exclude traumatic ICH, subdural hematomas, hemorrhage from cerebral venous thrombosis, and neoplasm-related hemorrhage 3
• Document potential etiologies including moyamoya syndrome/disease, vasculitis, drug-related causes, and oral antithrombotic use 3
• Monitor for complications including disturbance of cerebrospinal fluid circulation, hemorrhagic transformation, and midline shift 7

SAH Management:

• Record intracranial treatment modality, delayed cerebral ischemia complications, rebleeding, and seizures 3
• For intracranial aneurysms, document rupture status, multiplicity, location, size, and family history 3

Critical Pitfalls to Avoid

• Do not rely solely on clinical features without imaging for accurate stroke classification 4
• Do not combine TIA and stroke cases in classification systems; TIA requires symptom resolution within 24 hours and imaging to exclude acute infarct 3
• Do not perform lumbar puncture routinely; it is only indicated when infectious etiology is suspected and brain imaging is negative 3
• Do not miss cerebellar strokes: Patients with cerebellar symptoms should undergo HINTS examination (head-impulse, nystagmus, test of skew), which is more sensitive than early MRI 6
• Do not assume all patients have adequate acoustic bone windows for transcranial ultrasound; approximately 12% of patients have insufficient windows 7
• Location of infarct is more important than size in some cases; middle cerebral artery territory infarcts have poorer neurological recovery (50% vs 83% in non-MCA territories) 5