NEFL and Atrophy: Elevated levels of NfL and pNfH, both markers of neuronal injury and neurodegeneration, demonstrated high diagnostic performance.22 Previous research has shown that NfL is increased in symptomatic, but not presymptomatic, preSxC9 at the group level.23 Recent studies suggested that a slow increase in Nf levels can be observed in presymptomatic individuals who carry the mutation as far as 3.5 years before diagnosable illness,24,25,26 while another study described an association between higher NfL levels and GM atrophy.27