Year, Volume, Issue, Page(s):17, 27, 2, 199-207
Study investigated whether the extent of brainstem traumatic axonal injury (TAI), measured by the number of dorsal brainstem traumatic microbleeds (TMBs), correlates with 1-year functional outcome more strongly than does the number of TMBs in the ventral brainstem, corpus callosal, or entire brain. Further, it was hypothesized that TMBs within brainstem nuclei of the ascending arousal network (AAN) correlate with 1-year outcome. Recovery of functional independence is possible in patients with brainstem TAI, also referred to as "grade 3 diffuse axonal injury," but acute prognostic biomarkers are lacking. Data were collected from 39 patients who underwent acute gradient-recalled echo (GRE) magnetic resonance imaging as part of the Traumatic Brain Injury Model Systems study. TMBs were counted on the acute GRE scans globally and in the dorsal brainstem, ventral brainstem, and corpus callosum. TMBs were also mapped onto an atlas of AAN nuclei. The primary outcome was the Disability Rating Scale (DRS) score at 1 year post-injury. Associations between regional TMBs, AAN TMB volume, and 1-year DRS score were assessed by calculating Spearman rank correlation coefficients. Mean number of TMBs was: dorsal brainstem = 0.7, ventral brainstem = 0.2, corpus callosum = 1.8, and global = 14.4. The mean TMB volume within AAN nuclei was 6.1 millimeters cubed. Increased dorsal brainstem TMBs and larger AAN TMB volume correlated with worse 1-year outcomes. Global, callosal, and ventral brainstem TMBs did not correlate with outcomes. These findings suggest that dorsal brainstem TAI, especially involving AAN nuclei, may have greater prognostic utility than the total number of lesions in the brain or brainstem.