Radiologic kinetic patterns of spontaneous regression in acute traumatic subdural hematoma

Spontaneous regression of traumatic acute subdural hematoma (ASDH) is uncommon, and serial CT findings have been interpreted inconsistently across case-based reports. A structured kinetic framework may help organize temporal changes in hematoma burden, radiodensity, and mass effect. We constructed a curated case-based dataset of spontaneous regression of traumatic ASDH from published reports identified through a structured PubMed search (inception to December 31, 2025; no language restrictions). Because reporting quality and serial CT detail were heterogeneous, we selectively included cases with clearly documented serial CT (≥ 2 time points) enabling kinetic assessment using predefined operational definitions. Two institutional cases meeting the same criteria were analyzed in parallel. Across institutional cases and selected literature, radiologic kinetics aligned with two recurring phenotypes. One showed early reduction in hematoma burden with preserved density and parallel improvement in mass effect, compatible with pressure-driven redistribution. The other showed early density attenuation with delayed reduction in hematoma burden and/or mass effect, compatible with cerebrospinal fluid–mediated dilution. Overlapping features indicated a kinetic continuum rather than a single dominant mechanism. A radiologic kinetics–based framework provides a reproducible descriptive approach for comparing heterogeneous imaging observations in spontaneous ASDH regression. This perspective may facilitate shared interpretation of serial CT findings across cases and support future systematic investigations, without implying management recommendations or a single dominant mechanism.