Serial neuroimaging in infants with abusive head trauma: timing abusive injuries

Abstract

The appearance and evolution of neuroimaging abnormalities following abusive head trauma (AHT) is important for establishing the time frame over which these injuries might have occurred. From a legal perspective this frames the timing of the abuse and therefore identifies and excludes potential perpetrators. A previous pilot study involving 33 infants with AHT helped to refine the timing of these injuries but was limited by its small sample size. In the present study, the authors analyzed a larger group of 210 cases involving infants with AHT to chronicle the first appearance and evolution of radiological (CT, MRI) abnormalities. All children younger than 24 months admitted to the Penn State Hershey Medical Center with AHT over a 10-year period were identified from a medical record review; the time of injury was determined through an evaluation of the clinical records. All imaging studies were analyzed, and the appearance and evolution of abnormalities were chronicled on serial neuroimaging studies obtained in the days and weeks after injury. One hundred five infants with specific injury dates and available imaging studies were identified; a subset of 43 children additionally had documented times of injury. In infants with homogeneously hyperdense subdural hematomas (SDHs) on initial CT scans, the first hypodense component appeared within the SDH between 0.3 and 16 days after injury, and the last hyperdense subdural component disappeared between 2 and 40 days after injury. In infants with mixed-density SDHs on initial scans, the last hyperdense component disappeared between 1 and 181 days. Parenchymal hypodensities appeared on CT scans performed as early as 1.2 hours, and all were visible within 27 hours after the injury. Rebleeding into SDHs was documented in 17 cases (16%) and was always asymptomatic. Magnetic resonance imaging of the brain was performed in 49 infants. Among those with SDH, 5 patterns were observed. Patterns I and II reflected homogeneous SDH; Pattern I (T1 hyperintensity and T2/FLAIR hypointensity, "early subacute") more commonly appeared on scans performed earlier after injury compared with Pattern II (T1 hyperintensity and T2/FLAIR hyperintensity, "late subacute"), although there was considerable overlap. Patterns III and IV reflected heterogeneous SDH; Pattern III contained relatively equal mixtures having different intensities, whereas Pattern IV had fluid that was predominantly T1 hypointense and T2/FLAIR hyperintense. Again, Pattern III more commonly appeared on scans performed earlier after injury compared with Pattern IV, although there was significant overlap. These data extend the preliminary data reported by Dias and colleagues and provide a framework upon which injuries in AHT can be timed as well as the limitations on such timing estimates.