Allison E. Arch, MD

Kim and colleagues investigated the clinical significance of FLAIR vascular hyperintensities in watershed strokes, and they tried to predict poor prognosis using these FLAIR changes as a marker of impaired hemodynamics.

Watershed, or borderzone, strokes represent 10% of all ischemic infarcts. The authors of this study defined 2 types of borderzone strokes: internal borderzone infarcts (IBZ), which are lesions between the deep and superficial perforating arterial territories of the MCA, and cortical borderzone infarcts (CBZ), which are between the MCA/ACA or the MCA/PCA territories. A patient was then considered FLAIR-positive he had 2 or more FLAIR vascular hyperintensities in his MCA territory on MRI, which were thought to have occurred prior to the stroke.

Eighty-seven consecutive patients with acute borderzone strokes were identified, 62 with CBZ and 55 with IBZ. Thirty of all included stroke patients were considered FLAIR-positive. The authors found that FLAIR vascular hyperintensities were associated with a more severe clinical presentation and a poorer clinical prognosis in patients with CBZ strokes, but not in patients with IBZ strokes. They concluded the presence of FLAIR vascular hyperintensities, “may help to identify CBZ-infarcted patients who require close observation and hemodynamic control.”
Their findings are interesting. The authors noted that the presumed pathogenesis of watershed strokes is microembolization in combination with hemodynamic disturbance. However, in patients with FLAIR vascular hyperintensities on MRI, there may be an additional hemodynamic-compromised insult during the stroke, which then leads to poorer outcomes. Kim and colleagues pointed out that in the CBZ group, those who had FLAIR vascular hyperintensities had similar sized DWI lesions to those patients who did not have FLAIR lesions. However, there were significant perfusion differences between the FLAIR-positive and FLAIR-negative groups, lending support to the concept that FLAIR vascular hyperintensities on MRI may signify that the patient is more influenced by hemodynamic instability than his FLAIR-negative counterpart.

It is unclear why this would be on the case in CBZ strokes but not in IBZ strokes. Further investigations are needed to help elucidate the importance of hemodynamics in borderzone strokes.