NEFL and frontotemporal dementia: Patients with prodromal FTD had higher serum NfL levels compared with HC (average difference 14.5, 95% CI 2.9 to 26.1 pg/mL) but lower NfL levels than in patients with mild FTD (average difference − 15.5, 95% CI − 28.4 to − 2.7 pg/mL).