NEFL and early-onset autosomal dominant Alzheimer disease: Elevated serum NfL reflects a generalized process of neuronal damage rather than a disorder-specific signature, and this phenomenon has been documented across a broad spectrum of neurological and psychiatric conditions, including multiple sclerosis, Alzheimer’s disease, frontotemporal dementia, amyotrophic lateral sclerosis (ALS), traumatic brain injury, stroke [36,37,38], and status epilepticus [39].