MMP9 and brain ischemia: The increased MMP‐9 concentration in CSF after aSAH is a suggested biomarker for DCI (Triglia et al., 2016) and the elevated MMP‐9 after cerebral ischemia is associated with accelerated matrix degradation, disruption of the blood‐brain barrier, increasing the infarct size, and relating to hemorrhagic transformation (Dong, Song, Liu, & Guo, 2009; Turner & Sharp, 2016).