BACKGROUND - Determine the prognostic impact of magnetic resonance imaging (MRI)-defined diffuse axonal injury (DAI) after traumatic brain injury (TBI) on functional outcomes, quality of life, and 3-year mortality.
METHODS - This retrospective single center cohort included adult trauma patients (age > 17 years) admitted from 2006 to 2012 with TBI. Inclusion criteria were positive head computed tomography with brain MRI within 2 weeks of admission. Exclusion criteria included penetrating TBI or prior neurologic condition. Separate ordinal logistic models assessed DAI's prognostic value for the following scores: (1) hospital-discharge Functional Independence Measure, (2) long-term Glasgow Outcome Scale-Extended, and (3) long-term Quality of Life after Brain Injury-Overall Scale. Cox proportional hazards modeling assessed DAI's prognostic value for 3-year survival. Covariates included age, sex, race, insurance status, Injury Severity Score, admission Glasgow Coma Scale Score, Marshall Head computed tomography Class, clinical DAI on MRI (Y/N), research-level anatomic DAI Grades I-III (I, cortical; II, corpus callosum; III, brainstem), ventilator days, time to follow commands, and time to long-term follow-up (for logistic models).
RESULTS - Eligibility criteria was met by 311 patients, who had a median age of 40 years (interquartile range [IQR], 23-57 years), Injury Severity Score of 29 (IQR, 22-38), intensive care unit stay of 6 days (IQR, 2-11 days), and follow-up of 5 years (IQR, 3-6 years). Clinical DAI was present on 47% of MRIs. Among 300 readable MRIs, 56% of MRIs had anatomic DAI (25% Grade I, 18% Grade II, 13% Grade III). On regression, only clinical (not anatomic) DAI was predictive of a lower Functional Independence Measure score (odds ratio, 2.5; 95% confidence interval, 1.28-4.76], p = 0.007). Neither clinical nor anatomic DAI were related to survival, Glasgow Outcome Scale-Extended, or Quality of Life after Brain Injury-Overall Scale scores.
CONCLUSION - In this longitudinal cohort, clinical evidence of DAI on MRI may only be useful for predicting short-term in-hospital functional outcome. Given no association of DAI and long-term TBI outcomes, providers should be cautious in attributing DAI to future neurologic function, quality of life, and/or survival.
LEVEL OF EVIDENCE - Epidemiological, level III; Therapeutic, level IV.