Diffuse axonal injury (DAI) is an important cause of morbidity in patients with traumatic brain injury (TBI). There is currently no simple and reliable technique for early identification of patients with DAI, or to prognosticate long-term outcome in this patient group. In the present study, we examined acute serum concentrations of neurofilament light (NFL) in nine patients with severe TBI and DAI using a novel ultrasensitive single molecule array (Simoa) assay. The relationships between the NFL concentrations and MRI in the acute stage as well as clinical outcome and magnetic resonance diffusion tensor imaging (MR-DTI) parameters at 12 months were analyzed. We found that the mean NFL concentrations among the patients displayed a 30-fold increase compared with controls, and that NFL completely discriminated between the patients and controls. We also found a relationship between serum NFL and MR-DTI parameters, with higher NFL concentrations in patients with higher trace (R = 0.79) and lower fractional anisotropy (FA) (R = 0.83). These results suggest that serum NFL may be a valuable blood biomarker for TBI, reflecting the severity of DAI.

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