• Clinical science
  • Clinician

Ischemic stroke

Summary

Ischemic stroke is an acute neurologic condition caused by impaired cerebral blood flow (e.g., vascular occlusion or systemic hypoperfusion). Chronic systemic hypertension and cardiovascular disease are the most important risk factors. Clinically, ischemic stroke is characterized by the acute onset of focal neurologic deficits, which are dependent on the cerebral territory covered by the relevant vessel. A noncontrast head CT should immediately be performed to rule out intracranial hemorrhage. Revascularization of the vessels affected in ischemic strokes, for example via tissue plasminogen activator (tPA) or thrombectomy, is vital to preserving brain tissue. Secondary prevention is focused on managing modifiable risk factors (i.e., hypertension, atherosclerosis).

For more information, see overview of stroke, intracerebral hemorrhage, and subarachnoid hemorrhage.

Definition

References:[2][3][4]

Epidemiology

For both ischemic and hemorrhagic strokes, age is the most important nonmodifiable risk factor and arterial hypertension is the most important modifiable risk factor!

References:[5][6][7]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

References:[8][9][10][6][11][12][13][14][15]

Clinical features

Subtypes and variants

Transient ischemic attack [16]

Lacunar infarct [11][17]

Infarction of the posterior limb of the internal capsule is the most common type of lacunar stroke and may manifest clinically with pure motor stroke, pure sensory stroke (rare), sensorimotor stroke, dysarthria-clumsy hand syndrome, and/or ataxic hemiparesis.

Watershed infarct [6][18]

  • Definition: border-zone infarct in the region between the territory of two major arteries that supply the brain
  • Etiology: sudden decrease in blood pressure or cessation of blood flow through both vessels → ischemia in the susceptible region between two vascular territories
  • Clinical features
    • Signs of systemic hypoperfusion (e.g., tachycardia, low blood pressure, pallor, sweating)
    • Diffuse neurologic deterioration
    • Bilateral visual loss (cortical blindness)
    • Proximal limb weakness with sparing of the face, hands, and feet

Diagnostics

Initial evaluation

  • Determine the time of onset of symptoms: The time of stroke onset is used to determine treatment options (thrombolytic therapy).
  • Stabilize the patient if needed.
  • Check serum glucose.
  • Emergency imaging

Imaging

  1. Immediate noncontrast head CT to evaluate for acute hemorrhage prior to administration of thrombolytic therapy
  2. Further choice of imaging depends on head CT findings.
    • Diffusion-weighted MRI is a more sensitive test for acute ischemia (e.g., if head CT is negative but clinical suspicion for acute stroke is high).
    • Neurovascular studies (e.g., CTA or MRA) for more specific identification of the occluded vessel

The decision to obtain further imaging should not delay the administration of thrombolytic therapy in appropriate candidates!

Noncontrast CT

Diffusion-weighted MRI

Neurovascular studies

  • CT angiography (CTA)
    • Allows identification of the exact location of the defect (in most cases)
    • Indications
      • When there is a high index of suspicion for stroke but no ischemic changes are found on noncontrast CT or MRI.
      • If the patient cannot receive tPA (e.g., outside of the time window) but may be a candidate for mechanical thrombectomy (see “Treatment” below).
  • MRI angiography (MRA): indications similar to CTA

Laboratory evaluation [19]

Immediate imaging or administration of tPA for ischemic stroke should not be delayed to obtain laboratory studies!

Additional diagnostic workup

For more information on the diagnosis of other stroke types, see diagnosis of stroke.

References:[13][15][20][19]

Pathology

Patterns of necrosis in ischemic stroke [21]

Infarction of brain tissue is typically followed by liquefactive necrosis, in contrast to the coagulative necrosis seen after infarction in other organs.

Selective neuronal necrosis

Pan-necrosis

  • Definition: the death of all cell types in a given region of the brain, including neurons, glial cells, and vascular cells
  • Mechanism: permanent ischemia
  • Histology: cystic lesions and loss of tissue architecture

Histologic changes in the infarcted region [21][22]

Time from start of ischemia Histologic features
12–24 hours
1–3 days
3–5 days
5–15 days
> 15 days

References:[21][22]

Treatment

Reperfusion therapy

  • Goal is to prevent further tissue ischemia and irreversible infarction
  • Should be administered as soon as possible in eligible candidates (see below for specific indications)

Reperfusion therapy should not be delayed – “time is brain”! However, intracranial hemorrhage is a contraindication for reperfusion therapy and must be ruled out first.

IV thrombolytic therapy [19]

Intra-arterial thrombolysis [19]

  • Definition: intra-arterial (not intravenous) administration of a thrombolytic agent (e.g., prourokinase)
  • Indication: MCA stroke patients with onset of symptoms < 6 hours who are not eligible for IV thrombolytic therapy

Mechanical thrombectomy [19]

Blood pressure management [19]

Supportive care

Other

References:[9][23][10][24][15][25][26][27][19]

Acute management checklist

Complications

We list the most important complications. The selection is not exhaustive.

Prevention

The single most important treatable risk factor for secondary stroke prevention is hypertension! [12]

References:[23][12][29]

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last updated 09/21/2020
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