CHI3L1 and amyotrophic lateral sclerosis: While there is considerable overlap between neurodegenerative conditions, expression patterns differ, underscoring the different pathomechanisms at play; for instance, while CSF CHI3L1 increases as cognitive deficits worsen along the AD continuum, no similar associations have been noted with the ALSFRS-R, the primary indicator of disease severity in ALS (40).