Thresholds for the assessment of inflicted head injury by shaking trauma in infants: a systematic review

Abstract

In order to investigate potential causal relations between the shaking of infants and injuries, biomechanical studies compare brain and skull dynamic behavior during shaking to injury thresholds. However, performing shaking tolerance research on infants, either in vivo or ex vivo, is extremely difficult, if not impossible. Therefore, infant injury thresholds are usually estimated by scaling or extrapolating adult or animal data obtained from crash tests or whiplash experiments. However, it is doubtful whether such data accurately matches the biomechanics of shaking in an infant. Hence some thresholds may be inappropriate to be used for the assessment of inflicted head injury by shaking trauma in infants. A systematic literature review was conducted to 1) provide an overview of existing thresholds for headand neck injuries related to violent shaking, and 2) to identify and discuss which thresholds have been used or could be used for the assessment of inflicted head injury by shaking trauma in infants. Key findings: The majority of studies establishing or proposing injury thresholds were found to be based on loading cycle durations and loading cycle repetitions that did not resemble those occurring during shaking, or had experimental conditions that were insufficiently documented in order to evaluate the applicability of such thresholds. Injury thresholds that were applied in studies aimed at assessing whether an injury could occur under certain shaking conditions were all based on experiments that did not properly replicate the loading characteristics of shaking. Somewhat validated threshold scaling methods only exist for scaling concussive injury thresholds from adult primate to adult human. Scaling methods that have been used for scaling other injuries, or for scaling adult injury thresholds to infants were not validated. There is a clear and urgent need for new injury thresholds established by accurately replicating the loading characteristics of shaking.

Thrombosis is not a marker of bridging vein rupture in infants with alleged abusive head trauma

“…Recent reviews have concluded that thresholds, based on experiments or models, used to assess shaking trauma are of low quality and questionable use 56,57 …”

“…Recent reviews have concluded that thresholds, based on experiments or models, used to assess shaking trauma are of low quality and questionable use. 56,57 Zhu et al 58 conducted a combined autopsy and modelling study of 137 bridging veins from six adults. Based on bridging vein diameters and angles relative to the SSS, they calculated that venous thrombosis would occur more easily in wider bridging veins >1.2 mm, and when angles at the entry points were small (<65°).…”

Violent Infant Surrogate Shaking: Continuous High-Magnitude Centripetal Force and Abrupt Shift in Tangential Acceleration May Explain High Risk of Subdural Hemorrhage

“…Commonly used shaking injury thresholds have recently been called into question for various reasons. 19 Many such thresholds have not been properly validated for applicability to infants, and few take into account the very different loading patterns found in shaking versus impacts. Although impacts may cause large impulse transfers by short duration, high-intensity peaks, shaking may transfer just as large or even larger impulses with lower maximum forces, but over longer and repeated cycles.…”

Trends in Shaken Baby Syndrome Diagnoses Among Young Children Hospitalized for Abuse

“…2 Approximately 25% of SBS injuries are fatal, 1 and survivors may experience developmental delays, behavioral disorders, seizures, and loss of vision. 3−5 There is little consensus among physicians and researchers that shaking alone causes the injuries associated with SBS, 6 and the American Academy of Pediatrics (AAP) and the Center for Disease Control and Prevention (CDC) recommend pediatricians use the term AHT instead of SBS to avoid specifying a mechanism of injury. 7,8 Despite recommendations from AAP and CDC, medical professionals continue to diagnose SBS, suggesting that both AHT and SBS are relevant diagnoses and definitions of abuse.…”