Clinical Significance of Leakage Sign Patterns in Acute Subdural Hematoma

The leakage sign (LS), defined as contrast medium extravasation on the 5-minute delayed phase after computed tomography (CT) angiography, has been reported as a predictive imaging marker for hematoma expansion in acute subdural hematoma (ASDH). We recently identified two different patterns of LS: local and diffuse. This study aimed to evaluate the clinical importance of these LS types in predicting brain swelling and determining the appropriate surgical intervention. We retrospectively reviewed 98 patients with LS-positive ASDH on contrast-enhanced CT between January 2013 and September 2024. LS was classified as local-type when one or two positive areas were observed and as diffuse-type when three or more positive areas were present and/or when contrast medium extended along the brain surface. Brain swelling was defined based on radiological findings and the requirement for decompressive craniectomy. Clinical data, treatment modalities, and outcomes were analyzed in both groups. Among the 98 LS-positive patients, 40 were classified as having local-type and 58 as having diffuse-type. The diffuse-type LS group had a significantly greater proportion of patients in severe admission Glasgow Coma Scale category (p = 0.027), underwent decompressive craniectomy more frequently (p = 0.04), and had higher indicators of coagulopathy, including elevated activated partial thromboplastin time, prothrombin time-international normalized ratio, and D-dimer levels (all p < 0.05).　Brain swelling occurred in 70.7% of patients in the diffuse-type group compared with 17.5% in the local-type group (p < 0.001). Poor outcomes were significantly more common in the diffuse-type group (67.2% vs. 32.5%, p = 0.001), along with a higher mortality rate (56.9% vs. 22.5%, p < 0.001). Diffuse-type LS was independently associated with poor outcomes and was associated with clinical severity, coagulopathy, and brain swelling. Conversely, local-type LS was associated with favorable outcomes and a low rate of brain swelling. Because most patients with LS-positive ASDH show progressive ASDH, emergency hematoma evacuation is generally required. Patients with diffuse-type LS may be more likely to require decompressive craniectomy, whereas endoscopic hematoma removal via a small craniotomy may be a feasible option for local-type LS, where the bleeding point can be detected using the LS-positive area.