In this study, we hypothesize that (1) military veterans with TBI will have higher MRI-visible PVS number and cerebrospinal fluid (CSF) p-tau and Aβ42/40; (2) MRI-visible PVS would be associated with cognitive impairment, and CSF biomarkers will mediate this effect in military veterans with TBI. Here, MAPT is linked to Cognitive impairment.