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The shaken baby syndrome. A clinical, pathological, and biomechanical study
Insights
Severe head injuries in infants, often called shaken baby syndrome, typically require direct impact, not just shaking. Shaking alone is unlikely to cause these severe brain injuries.
Area of Science:
- Pediatrics
- Forensic Pathology
- Biomechanics
Background:
- Diagnosis of abusive head trauma (AHT) often lacks a history of shaking.
- AHT diagnosis relies on clinical and radiographic findings, including retinal and subdural hemorrhages.
- Previous studies often attributed AHT solely to shaking.
Purpose of the Study:
- To investigate the biomechanical forces involved in abusive head trauma.
- To determine if shaking alone can cause injuries consistent with shaken baby syndrome.
- To differentiate between injury mechanisms in AHT cases.
Main Methods:
- Retrospective review of 48 infant cases diagnosed with AHT.
- Analysis of clinical, radiographic, and autopsy findings.
- Biomechanical modeling of infant head impacts and shaking using accelerometers.
Main Results:
- All fatal AHT cases showed signs of blunt head impact, often only evident at autopsy.
- Fatalities were associated with increased intracranial pressure.
- Biomechanical models showed shaking forces were 50 times lower than impact forces and below injury thresholds for primates, while impacts caused injuries.
Conclusions:
- Severe head injuries diagnosed as AHT necessitate impact.
- Shaking alone is unlikely to cause shaken baby syndrome in otherwise healthy infants.
- Impact forces are the primary mechanism for severe head injuries in AHT.
Abstract:
Because a history of shaking is often lacking in the so-called "shaken baby syndrome," diagnosis is usually based on a constellation of clinical and radiographic findings. Forty-eight cases of infants and young children with this diagnosis seen between 1978 and 1985 at the Children's Hospital of Philadelphia were reviewed. All patients had a presenting history thought to be suspicious for child abuse, and either retinal hemorrhages with subdural or subarachnoid hemorrhages or a computerized tomography scan showing subdural or subarachnoid hemorrhages with interhemispheric blood. The physical examination and presence of associated trauma were analyzed; autopsy findings for the 13 fatalities were reviewed. All fatal cases had signs of blunt impact to the head, although in more than half of them these findings were noted only at autopsy. All deaths were associated with uncontrollably increased intracranial pressure. Models of 1-month-old infants with various neck and skull parameters were instrumented with accelerometers and shaken and impacted against padded or unpadded surfaces. Angular accelerations for shakes were smaller than those for impacts by a factor of 50. All shakes fell below injury thresholds established for subhuman primates scaled for the same brain mass, while impacts spanned concussion, subdural hematoma, and diffuse axonal injury ranges. It was concluded that severe head injuries commonly diagnosed as shaking injuries require impact to occur and that shaking alone in an otherwise normal baby is unlikely to cause the shaken baby syndrome.