Moreover, we have applied this new assay to quantify NfL in the CSF of patients with a variety of neurological disorders, including inflammatory demyelinating diseases (IDD) of the CNS, AD, including both mild cognitive impairment due to AD (MCI-AD) and probable AD dementia (AD-dem), Parkinson’s disease (PD) and other neurological noninflammatory and non-neurodegenerative diseases (OND). Here, NEFL is linked to intervertebral disk degenerative disorder.