Whiteout sign on dSIR MRI: A case series highlighting symptom-associated white matter changes not observed on standard T 2 -FLAIR

INTRODUCTION: Mild traumatic brain injury (mTBI) is common, and up to half of patients experience persistent symptoms, but conventional neuroimaging typically appears normal. Divided Subtracted Inversion Recovery (dSIR) is a new sequence with high sensitivity to white matter changes that may appear normal on standard imaging. CASE PRESENTATION: -FLAIR images were normal. In two symptomatic cases, dSIR demonstrated a 'whiteout sign,' with bilateral, symmetrical high signal in cerebral and cerebellar white matter. In one case, the whiteout sign was present at 21 hours post-injury and had largely resolved by 64 hours. The third patient showed no abnormality on dSIR, consistent with their asymptomatic clinical presentation. Across all three cases, dSIR findings corresponded to clinical symptom status at the time of scanning. CONCLUSION: These early observations suggest dSIR may provide a useful imaging marker of secondary brain responses to injury. Further studies are needed to determine the sensitivity, specificity, and clinical value of dSIR in the assessment of mTBI.