Wake-up stroke: clinical characteristics, imaging findings, and treatment option - an update

Abstract

About 25% of all strokes occur during sleep, i.e., without knowledge of exact time of symptom onset. According to licensing criteria, this large group of patients is excluded from treatment with received tissue-plasminogen activator, the only specific stroke treatment proven effective in large randomized trials. This paper reviews clinical and imaging characteristics of wake-up stroke and gives an update on treatment options for these patients. From clinical and imaging studies, there is evidence suggesting that many wake-up strokes occur close to awakening and thus, patients might be within the approved time-window of thrombolysis when presenting to the emergency department. Several imaging approaches are suggested to identify wake-up stroke patients likely to benefit from thrombolysis, including non-contrast CT, CT-perfusion, penumbral MRI, and the recent concept of diffusion weighted imaging-fluid attenuated inversion recovery (DWI-FLAIR). A number of small case series and observational studies report results of thrombolysis in wake-up stroke, and no safety concerns have occurred, while conclusions on efficacy cannot be drawn from these studies. To this end, there are ongoing clinical trials enrolling wake-up stroke patients based on imaging findings, i.e., the DWI-FLAIR-mismatch (WAKE-UP) or penumbral imaging (EXTEND). The results of these trials will provide evidence to guide thrombolysis in wake-up stroke and thus, expand treatment options for this large group of stroke patients.

Keywords: DWI-FLAIR-mismatch; acute ischemic stroke; computed tomography; fluid attenuated reversion recovery; magnetic resonance imaging; thrombolysis; wake-up stroke.

Figure 1

MRI perfusion–diffusion mismatch. The small lesion on diffusion weighted imaging (DWI) represents the infarct core, while the much larger area in the time to peak map calculated from perfusion imaging (PWI) identifies the area of critically hypoperfused tissued. The mismatch between both volumes represents the tissue at risk of infraction and thus, the target tissue for reperfusion treatment.

Figure 2

DWI-FLAIR-mismatch. The upper row gives two examples of a clearly visible acute ischemic lesion on diffusion weighted imaging (DWI), while no marked parenchymal hyperintensity is detected on fluid attenuated inversion recovery (FLAIR) images indicating DWI-FLAIR-mismatch. In the lower row, a clear hyperintensity can be seen on FLAIR images in the area of the acute DWI lesion (no DWI-FLAIR-mismatch).