RESUMO
Introduction: Although cerebral edema is common following traumatic brain injury (TBI), its formation and progression are poorly understood. This is especially true for the mild TBI population, who rarely undergo magnetic resonance imaging (MRI) studies, which can pick up subtle structural details not visualized on computed tomography, in the first few days after injury. This study aimed to visually classify and quantitatively measure edema progression in relation to traumatic microbleeds (TMBs) in a cohort of primarily mild TBI patients up to 30 days after injury. Researchers hypothesized that hypointense lesions on Apparent Diffusion Coefficient (ADC) detected acutely after injury would evolve into hyperintense Fluid Attenuated Inversion Recover (FLAIR) lesions. Methods: This study analyzed the progression of cerebral edema after acute injury using multimodal MRI to classify TMBs as potential edema-related biomarkers. ADC and FLAIR MRI were utilized for edema classification at three different timepoints: ≤48 hours, ~1 week, and 30 days after injury. Hypointense lesions on ADC (ADC+) suggested the presence of cytotoxic edema while hyperintense lesions on FLAIR (FLAIR+) suggested vasogenic edema. Signal intensity Ratio (SIR) calculations were made using ADC and FLAIR to quantitatively confirm edema progression. Results: Our results indicated the presence of ADC+ lesions ≤48 hours and ~1 week were associated with FLAIR+ lesions at ~1 week and 30 days, respectively, suggesting some progression of cytotoxic edema to vasogenic edema over time. Ten out of 15 FLAIR+ lesions at 30 days (67%) were ADC+ ≤48 hours. However, ADC+ lesions ≤48 hours were not associated with FLAIR+ lesions at 30 days; 10 out of 25 (40%) ADC+ lesions ≤48 hours were FLAIR+ at 30 days, which could indicate that some lesions resolved or were not visualized due to associated atrophy or tissue necrosis. Quantitative analysis confirmed the visual progression of some TMB lesions from ADC+ to FLAIR+. FLAIR SIRs at ~1 week were significantly higher when lesions were ADC+ ≤48 hours (1.22 [1.08-1.32] vs 1.03 [0.97-1.11], p=0.002). Conclusion: Awareness of how cerebral edema can evolve in proximity to TMBs acutely after injury may facilitate identification and monitoring of patients with traumatic cerebrovascular injury and assist in development of novel therapeutic strategies.
RESUMO
Magnetic resonance imaging (MRI) is used rarely in the acute evaluation of traumatic brain injury (TBI) but may identify findings of clinical importance not detected by computed tomography (CT). We aimed to characterize the association of cytotoxic edema and hemorrhage, including traumatic microbleeds, on MRI obtained within hours of acute head trauma and investigated the relationship to clinical outcomes. Patients prospectively enrolled in the Traumatic Head Injury Neuroimaging Classification study (NCT01132937) with evidence of diffusion-related findings or hemorrhage on neuroimaging were included. Blinded interpretation of MRI for diffusion-weighted lesions and hemorrhage was conducted, with subsequent quantification of apparent diffusion coefficient (ADC) values. Of 161 who met criteria, 82 patients had conspicuous hyperintense lesions on diffusion-weighted imaging (DWI) with corresponding regions of hypointense ADC in proximity to hemorrhage. Median time from injury to MRI was 21 (10-30) h. Median ADC values per patient grouped by time from injury to MRI were lowest within 24 h after injury. The ADC values associated with hemorrhagic lesions are lowest early after injury, with an increase in diffusion during the subacute period, suggesting transformation from cytotoxic to vasogenic edema during the subacute post-injury period. Of 118 patients with outcome data, 60 had Glasgow Outcome Scale Extended scores ≤6 at 30/90 days post-injury. Cytotoxic edema on MRI (odds ratio [OR] 2.91 [1.32-6.37], p = 0.008) and TBI severity (OR 2.51 [1.32-4.74], p = 0.005) were independent predictors of outcome. These findings suggest that in patients with TBI who had findings of hemorrhage on CT, patients with DWI/ADC lesions on MRI are more likely to do worse.
