Association of Optical Coherence Tomography With Longitudinal Neurodegeneration in Veterans With Chronic Mild Traumatic Brain Injury

• Published in: JAMA network open 2020-12, Vol.3 (12), p.e2030824-e2030824
• Main Authors: Gilmore, Casey S, Lim, Kelvin O, Garvin, Mona K, Wang, Jui-Kai, Ledolter, Johannes, Fenske, Alicia L, Gentz, Carolyn L, Nellis, Julie, Armstrong, Michael T, Kardon, Randy H
• Format: Article
• Language: English
• Subjects: Biomarkers; Brain Concussion - complications; Brain Concussion - physiopathology; Chronic Disease; Cognition; Female; Functional Status; Humans; Longitudinal Studies; Male; Middle Aged; Neurodegeneration; Neurodegenerative Diseases - diagnosis; Neurodegenerative Diseases - etiology; Neurodegenerative Diseases - psychology; Neurology; Neuropsychological Tests - statistics & numerical data; Online Only; Original Investigation; Tomography; Tomography, Optical Coherence - methods; Traumatic brain injury; United States - epidemiology; Veterans; Veterans Health - statistics & numerical data; Visual Field Tests - methods; Visual Field Tests - statistics & numerical data
• ISSN: 2574-3805; 2574-3805
• DOI: 10.1001/jamanetworkopen.2020.30824

Mild traumatic brain injury (TBI) may predispose individuals to progressive neurodegeneration. To identify evidence of neurodegeneration through longitudinal evaluation of changes in retinal layer thickness using optical coherence tomography in veterans with a history of mild TBI. This longitudinal cohort study evaluated veterans who were receiving services at the Minneapolis Veterans Affairs Health Care System. Symptomatic or mild TBI was diagnosed according to the Mayo TBI Severity Classification System. Participants in the age-matched control group had no history of TBI. Participants with any history or evidence of retinal or optic nerve disease that could affect retinal thickness were excluded. Data analysis was performed from July 2019 to February 2020. The presence and severity of mild TBI were determined through consensus review of self-report responses during the Minnesota Blast Exposure Screening Tool semistructured interview. Change over time of retinal nerve fiber layer (RNFL) thickness. A total of 139 veterans (117 men [84%]; mean [SD] age, 49.9 [11.1] years) were included in the study, 69 in the TBI group and 70 in the control group. Veterans with mild TBI showed significantly greater RNFL thinning compared with controls (mean [SE] RNFL slope, -1.47 [0.24] μm/y vs -0.31 [0.32] μm/y; F1,122 = 8.42; P = .004; Cohen d = 0.52). Functionally, veterans with mild TBI showed greater declines in visual field mean deviation (mean [SE] slope, -0.09 [0.14] dB/y vs 0.46 [0.23] dB/y; F1,122 = 4.08; P = .046; Cohen d = 0.36) and pattern standard deviation (mean [SE] slope, 0.09 [0.06] dB/y vs -0.10 [0.07] dB/y; F1,122 = 4.78; P = .03; Cohen d = 0.39) and high spatial frequency (12 cycles/degree) contrast sensitivity compared with controls. Cognitively, there was a significantly greater decrease in the number of errors over time during the Groton Maze Learning Test (GMLT) in controls compared with veterans with mild TBI (mean [SE] slope, -9.30 [1.48] errors/y vs -5.23 [1.24] errors/y; F1,127 = 4.43; P = .04; Cohen d = 0.37). RNFL tissue loss was significantly correlated with both worsening performance on the GMLT over time (Spearman ρ = -0.20; P = .03) and mild TBI severity (Spearman ρ = -0.25; P = .006). The more severe the mild TBI (larger Minnesota Blast Exposure Screening Tool severity score), the faster the reduction in RNFL thickness (ie, the more negative the slope) across time. This cohort study found longitudinal evidence for significant, progressive