MMP9 and amyotrophic lateral sclerosis: Similar results were found by the Beuche et al. (2000) who also revealed significantly elevated MMP-9 concentrations in the sera of ALS patients than in healthy controls, although the levels of MMP-9 increased up to levels as high as those of viral meningoencephalitis or bacterial meningitis patients and remained elevated during long-term observation of ALS patients (Beuche et al. 2000).