Imaging description

Brain infarcts in the subacute stage demonstrate enhancement and may mimic enhancing tumors or infectious processes (Fig. 5.1). Enhancement of the infarcted brain parenchyma is different than “luxury perfusion,” which involves enhancement of the vessels around the infarct in the acute phase. Infarcted tissue enhancement usually starts approximately 4–5 days after the insult and may increase in the following week [1]. Edema associated with infarcts peaks around the fourth day and starts dissipating afterwards, although some level of swelling of the infarcted tissue is usually present for approximately 2 weeks. Diffusion-weighted imaging (DWI) signal increase (apparent diffusion coefficient [ADC] signal decrease) is seen shortly after the infarct, peaks around the second day and gradually diminishes afterwards, with ADC normalization occurring around day 10. Brain MRI performed 5–14 days after the infarct may show an enhancing lesion with swelling and relative lack or absence of ADC signal decrease that might lead to an erroneous diagnosis.

Importance

Enhancing mass-like lesions of the brain usually require extensive work-up that frequently involves invasive procedures which may be harmful. Misdiagnosing an infarct leads not only to unnecessary work-up but also to delay in identifying and treating the underlying cause of the infarct for secondary stroke prevention.