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Subacute Cerebral Infarction


KEY FACTS

Terminology

  • Subacute infarction ~ 2-14 days following initial ischemic event

Imaging

  • Best diagnostic clue: Gyral edema and enhancement within basal ganglia and cortex

  • Typically wedge-shaped abnormality involving gray and white matter within vascular distribution

  • Hemorrhagic transformation of initially ischemic infarction occurs in 20-25% of middle cerebral artery occlusions, usually by 48-72 h

  • “2-2-2” rule = enhancement begins at 2 days, peaks at 2 weeks, disappears by 2 months

  • MRS: ↑ lactate, ↓ NAA within infarcted tissue

  • DWI: ↑ diffusion restriction, ↓ ADC initially, reversing as it proceeds into/through subacute stage

  • “Fogging” effect = normal T2WI with striking enhancement on T1WI C+ 1-2 weeks following ictus

Top Differential Diagnoses

  • Neoplasm

  • Venous infarction

  • Encephalitis/cerebritis

Clinical Issues

  • Acute-onset focal neurologic deficit

  • Elderly patient with typical risk factors: Hypertension, diabetes, smoking history, obesity, hypercholesterolemia

  • 1st month after infarction, mortality predominantly from neurologic complications; 1:4 die of recurrent stroke event

  • Acute anticoagulation after 1st infarction reduces mortality

Diagnostic Checklist

  • Enhancement is key to defining subacute stage of cerebral infarction

  • Subacute ischemia often mimics neoplasm

    • Recommend short-term follow-up to ensure expected course of evolution

Axial CT obtained 48 h after initial onset of weakness and speech difficulties shows the classic appearance of an early subacute cerebral infarct. Note the wedge-shaped, low-density area
involving both the gray and white matter in the left middle cerebral artery distribution.

Axial FLAIR MR in a 58-year-old man 1 week after onset of visual changes shows classic imaging of a subacute infarct with hyperintensity in the cortex and subcortical WM of the occipital lobe
in a posterior cerebral artery (PCA) distribution.

Axial DWI in the same patient shows hyperintensity within the left PCA distribution. The hyperintensity represents a combination of true diffusion restriction and T2 shine through.

Axial T1 C+ MR in the same patient shows gyriform enhancement along the cortex of the occipital lobe
. This enhancement may be seen as early as 2 days and may last up to 2 months after the patient's initial ischemic event. Without clinical history, imaging may mimic a tumor, venous infarct, or cerebritis.

TERMINOLOGY

Abbreviations

  • Subacute stroke, subacute cerebrovascular accident (CVA)

Definitions

  • Focal brain necrosis following obstruction of blood flow to localized area of brain

  • Subacute infarct ~ 2-14 days following initial ischemic event

  • May occur ± hemorrhagic transformation (HT)

IMAGING

General Features

  • Best diagnostic clue

    • Gyral edema, enhancement in basal ganglia/cortex

    • Look for hemorrhagic transformation

      • –

        Typically occurs in 20-25% of cases 2-7 days after acute event

  • Location

    • Cerebral hemispheres, brainstem, cerebellum in territorial vascular distribution

  • Size

    • Extremely variable

    • Ranges from focal (“lacunes”) to global (hemispheric)

  • Morphology

    • Variable depending on location, size, etiology

    • Typically wedge shaped; involves both gray and white matter

      • –

        Recognizable vascular distribution

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