Shaken baby syndrome

Shaken baby syndrome (SBS), also known as abusive head trauma (AHT), is a controversial medical condition in children younger than five years old, hypothesized to be caused by blunt trauma, vigorous shaking, or a combination of both.

According to medical literature, the condition is caused by violent shaking with or without blunt impact that can lead to long-term health consequences for infants or children. Diagnosis can be difficult, but is generally characterized by the triad of findings: retinal hemorrhage, encephalopathy, and subdural hematoma. A CT scan of the head is typically recommended if a concern is present. If there are concerning findings on the CT scan, a full work-up for child abuse often occurs, including an eye exam and skeletal survey. Retinal hemorrhage is highly associated with AHT, occurring in 78–85% of cases of AHT versus 5% of cases of non-abusive head trauma, although such findings rely on contested methodology. A 2023 review concluded "research has shown the triad is not sufficient to infer shaking or abuse and the shaking hypothesis does not meet the standards of evidence-based medicine", and argued the symptoms may arise from naturally occurring retinal haemorrhage.

The concept is controversial in child abuse pediatrics, with critics arguing it is an unproven hypothesis that has little diagnostic accuracy. Diagnosis has proven to be both challenging and contentious for medical professionals because objective witnesses to the initial trauma are generally unavailable, and when independent witnesses to shaking are available, the injuries comprising the traditional SBS triad occur at lower rates. This is said to be particularly problematic when the trauma is deemed "non-accidental". Some medical professionals propose that SBS is the result of respiratory abnormalities leading to hypoxia and swelling of the brain. Symptoms of SBS may also be non-specific markers of the degree of intracranial pathology. The courtroom has become a forum for conflicting theories with which generally accepted medical literature has not been reconciled. There are often no outwardly visible signs of trauma, despite the presence of severe internal brain and eye injury.

According to proponents, SBS is the leading cause of fatal head injuries in children under two, with a risk of death of about 18-25% of hospitalised cases. This figure has been criticized for circular reasoning and selection bias. Systematic case reviews have documented that shaking alone can cause subdural hemorrhages, retinal hemorrhages, and acute neurological symptoms consistent with abusive head trauma, though studies suggest that impacts generally produce more severe intracranial pathologies than shaking. The most common symptoms are said to be retinal bleeds, multiple fractures of the long bones, and subdural hematomas (bleeding in the brain). Educating new parents appears to be beneficial in decreasing rates of the condition, although other studies have shown that education does not change rates. SBS is estimated to occur in three to four per 10,000 babies per year.

Some experts state that retinal hemorrhage (bleeding) being a common symptom is based on circular reasoning and selection bias. RHs are very rare when infants are actually witnessed to have been shaken. The type of retinal bleeds are often believed to be particularly characteristic of this condition, making the finding useful in establishing the diagnosis, although the former studies may suggest the contrary.

Infants may display irritability, failure to thrive, alterations in eating patterns, lethargy, vomiting, seizures, bulging or tense fontanelles (the soft spots on a baby's head), increased size of the head, altered breathing, and dilated pupils, although all these clinical findings are generic and are known to have a range of causes, with shaking certainly not the most common cause of any of them. Complications include seizures, visual impairment, hearing loss, epilepsy, cerebral palsy, cognitive impairment, cardiac arrest, coma, and death.