Background: Subdural hematoma (SDH) is a common finding in patients with acute traumatic brain injury (TBI). Traumatic meningeal enhancement (TME) of the subdural space is visible on post-contrast MRI following administration of gadolinium. TME has since been described in patients with SDH, suggesting overlapping pathophysiology. It is unclear if TME is in the continuum of a SDH, or if it is a distinct injury. Given the current debate, we explored the relationship of SDH and TME to determine whether TME is a marker of a SDH, or whether TME is a distinct entity.

Methods: This retrospective analysis included a subset of consented patients (n=151) that were identified to have post-contrast MRI scans within 48 hours of injury who were selected from the Traumatic Head Injury Neuroimaging Classification (THINC) study. One rater reviewed Gradient Echo (GRE), pre-contrast fluid-attenuated inversion recovery (FLAIR) and post-contrast FLAIR axial brain MRI. Cohen’s kappa was performed. Discordant pairs found during the intra-rater agreement analysis were reviewed by a second independent rater. Areas where SDH was present were inspected for TME. SDH presence outside of TME areas was also noted. Following the rating, study data was reviewed to verify accuracy of interpretation. Contingency tables (2x2) were constructed to analyze reading results.

Results: Cohen’s kappa demonstrated intrareader and interreader agreement for SDH and TME was substantial (Kappa of 0.9, Kappa of 0.8). Initially, 91 SDH were identified. After reviewing radiologist and prior image interpretations, 20 cases were discordant. Of those, 17 were reclassified as SDH absent, 2 were reclassified SDH present, and 1 did not receive contrast and was excluded from analysis. Of the 150 included patients (99 Males, 51 Females, median age 49 30-63.8), 107 (71.3%) had TME, 77 (51.3%) had SDH, and 76 (50.7%) had both. 98.7% of patients with SDH also had TME present (p<0.001). Of these, 72 (94.7%) had SDH and TME overlapping in at least one area. Inversely, only 71% of patients with TME also had SDH present (p<0.001). Only 15.9% of patients with TME had no evidence of brain hemorrhage, and 1 showed SDH with no TME (p<0.001).

Conclusion: In our population TME was seen without SDH in 31 of 107 cases, SDH and TME were seen together in 76 of 77 cases, but seldom is SDH seen without TME. They likely represent very similar pathophysiology, and the discordance may reflect a spectrum of severity of injury.