MMP9 and amyotrophic lateral sclerosis: MMP9 polymorphisms are among the principal risk factors for sporadic ALS (Zawislak et al. 2009; Pabian-Jewula and Rylski 2023), with results of postmortem studies of ALS patients showing MMP9 levels ~ 2.5-fold lower in the oculomotor nucleus as compared to lumbar MNs (Brockington et al. 2013).