Dating the abusive head trauma episode and perpetrator statements: key points for imaging.

Shaken baby syndrome/abusive head trauma is a leading cause of morbidity and mortality in infants. The presence of a diffuse subdural hematoma without evidence of accident is a key diagnostic clue. The hematoma is typically attributed to rupture of the cerebral bridging veins due to violent shaking, with or without impact. Dating the incident, however, remains controversial. The aim of this article is to review the most reliable features used for dating the incident, based on both legal statements by perpetrators and medical documentation. The key points are: 1) The high (yet likely underestimated) frequency of repeated shaking is around 50%, 2) Children do not behave normally immediately after shaking, and the time of onset of even mild symptoms appears to be the best clue for dating the incident and 3) Brain imaging provides strong indicators of "age-different" injuries but the ranges for dating the causal event are wide. The density pattern in a single subdural hematoma location provides no reliable clues for assessing repeated violence. Only the finding of different density in two distant subdural hematomas argues in favor of "age-different" injuries, i.e. repeated violence. MRI is difficult to interpret in terms of dating subdural hemorrhages and must be analyzed in conjunction with CT. Most importantly, all of the child's previous clinical and radiological data must be carefully studied and correlated to provide accurate information on the date and repetition of the trauma.