MMP9 and HHV-6 encephalitis: On the other hand, an increase in serum concentrations of TIMP-1, but not MMP-9 of the MMP-9/TIMP-1 ratio has been reported in patients with central nervous disorders, such as cerebral infarction, cranial hemorrhage, traumatic brain injury, hemolytic-uremic syndrome, and HHV-6 encephalitis [2,8,9,10,11,12].