Displaced Cortical Vein Sign on CT: A Reliable Predictor to Distinguish Low Attenuation Subdural Collections from Benign Enlargement of Subarachnoid Spaces

Background Differentiating benign enlargement of subarachnoid spaces (BESS) from low attenuation subdural collections (SDC) on CT imaging can be challenging. The distinction between SDC and BESS is crucial in children, as SDC may raise the concern for non-accidental trauma (NAT). Objectives To evaluate the utilization of the displaced cortical vein sign on CT as a predictor of a pathological subdural collection confirmed by MRI and assesses the reproducibility of this finding between radiologists with different levels of clinical experience. Methods and Materials: A total of 104 imaging exams were independently reviewed by a junior and senior level radiologist ( 52 head CTs and 52 corresponding brain MRI exams). These exams included 43 MRI confirmed cases of SDC and 9 MRI confirmed cases of BESS from patients aged 0–2 years. The presence of pathological collections, sulci flattening, the displaced cortical vein sign, and the presence of thrombosed bridging veins were recorded for both reviewers along with attenuation and signal characteristics of the collections. Confirmed diagnosis of NAT was determined by chart review. The sensitivity, specificity, and inter-observer reliability were analyzed between reviewers. Results The average patient age was 6.4 months with a median age of 4 months. The sensitivity of the displaced cortical vein sign on CT for the presence of SDC confirmed by MRI was 79.0% and 69.6% for the two reviewers respectively. The specificity of this finding was 100% for both reviewers, with no false negative cases. Interobserver reliability was the highest among all features analyzed for the depiction of the displaced cortical vein sign on CT (κ = 0.63, 95% CI 0.45–0.82) and MRI (κ = 0.96, 95% CI 0.87-1.00). All cases where at least 1 reviewer noted the displaced cortical vein sign on CT and were later confirmed to be traumatic SDC on MRI were concluded to have high concern for NAT upon further chart review. Conclusions The displaced cortical vein sign on head CT is a specific and reproducible finding associated with subdural collections. Our data suggests that this sign is a more reliable and readily identifiable finding of pathological subdural collections compared to other traditional imaging findings, such as flattening of the cerebral sulci or bridging vein thrombosis. The displaced cortical vein sign when present on head CT should raise suspicion for NAT.