Deng et al. [5] reported that the ERK1/2 pathway inhibitor U0126 and the calcium channel blocker ketamine can suppress ERK1/2 phosphorylation, block miRNA-21 and matrix metalloproteinase-9 (MMP-9) expression and inhibit the inflammatory response to relieve the damage to the blood-brain barrier (BBB) and brain edema. Here, MMP9 is linked to brain edema.