OBJECTIVE: To determine if CNS-derived proteins present in the CSF of multiple 
sclerosis (MS) patients reflect different pathologic processes of MS and if 
these proteins could be useful as biologic markers of disease activity.
METHODS: Concentrations of the neurofilament light protein (NFL), glial 
fibrillary acidic protein (GFAP), S100B, and the neuron-specific enolase protein 
(NSE) were determined in the CSF of 66 MS patients and 50 healthy control 
subjects with immunoassays.
RESULTS: The mean levels of the NFL were increased during all stages of MS 
compared with controls (p < 0.001), peaking almost 10 times higher during acute 
relapses. The highest levels of GFAP were found during the secondary progressive 
course (p < 0.001) with a strong correlation with neurologic deficits (Expanded 
Disability Status Scale score, r = 0.73, p < 0.001). No increase of S100B or NSE 
protein was found in the CSF of MS patients compared with control subjects.
CONCLUSIONS: Increased level of NFL is a general feature of MS, indicating 
continuous axonal damage during the entire course of the disease with the most 
profound damage during acute relapses. GFAP may serve as a biomarker for disease 
progression, probably reflecting the increasing rate of astrogliosis.