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.
History In 1971, Norman Guthkelch proposed that whiplash injury caused subdural bleeding in infants by tearing the veins in the subdural space. The term whiplash shaken infant syndrome was introduced by John Caffey, a pediatric radiologist, in 1973, describing a set of symptoms found with little or no external evidence of head trauma, including retinal bleeds and intracranial bleeds with subdural or subarachnoid bleeding or both. Development of computed tomography and magnetic resonance imaging techniques in the 1970s and 1980s advanced the ability to diagnose the syndrome. In 1997, shaken baby syndrome was brought into the national spotlight with the trial of Louise Woodward.
Epidemiology The incidence of shaken baby syndrome is unknown due to difficulty in diagnosis, which may be caused by lack of centralized reporting system, absent signs of maltreatment, unclear presentation, and acute head trauma being classified under chronic neglect. Incidence is estimated to be 35 out of 100,000 infants, 65% of these infants have significant neurological disabilities, and 5–35% of infants die as a result of sustained injuries. For children under the age of one, US-based studies have found rates of 27.5 out of 100,000 infants for the years 1997 and 2000 and a rate of 32.2 out of 100,000 in the year 2003. However, these statistics are presumably underestimates of the actual incidence of SBS, because there are children whose injuries may not be perceived as serious enough to be hospitalized, and those who have been hospitalized but diagnosis was missed. On the other hand, there may be significant overdiagosis of SBS, which would make these findings an over-estimate.
Small children are at particularly high risk for abuse associated with SBS given the large difference in size between the small child and the caretaker. SBS is primarily observed in children under the age of two but may occur in those up to age five. The majority of cases typically occur before the infant's first birthday with the average victim age between three and eight months old. In the US, deaths due to SBS constitute about 10% of deaths due to child abuse.
Risk factors Common risk factors for shaken baby syndrome include perceived excessive crying, behavioral health problems, domestic violence history, frustration intolerance, lack of childcare experience, young infant age, young maternal age, multiple births, having a male infant, full-time working, postpartum depression, single parent families and economic adversity. The perpetrators of acute head trauma typically involve the father, stepfather, mother's boyfriend, female babysitter and the mother. The age group from child birth to the age of 4 are at greater risk of SBS due to multiple factors, including disproportionate anatomy, lack of or inability to communicate needs, and inability to protect self from a larger adult.
Episodes of colic are greatest at 6 to 8 weeks of age, and studies have shown a peak in SBS incidence during this time as parents may perceive these episodes as excessive crying. Caregivers that are at risk for becoming abusive often have unrealistic expectations of the child and may display "role reversal", expecting the child to fulfill the needs of the caregiver. Substance abuse and emotional stress, resulting for example from low socioeconomic status or family instability, are other risk factors for aggression and impulsiveness in caregivers. Caregivers of any gender can cause SBS, but cases of SBS have been reported to be more common amongst younger parents. Studies have shown increased prevalence of SBS among parents 34 years old or younger, especially 24 years old or younger. Although it had been previously speculated that SBS was an isolated event, evidence of prior child abuse is a common finding. In an estimated 33–40% of cases, evidence of prior head injuries, such as old intracranial bleeds, is present.
At the community level, risk factors for shaken baby syndrome include social isolation, lack of recreational facilities, lack of external support from family or governmental agencies, unsafe neighborhoods and societal factors such as poverty.
Mechanism Shaken Baby Syndrome, also known as Shaken Impact Syndrome, is a severe form of child abuse. It occurs when parents or caregivers shake a baby. There is a strong association between crying and SBS, where studies indicate 1–6% of parents have shaken their babies to stop crying. Furthermore, the caregiver's worries and views on crying are more predictive of shaking than the objective amount of crying. Evidence indicates early crying pattern as the common trigger for SBS, and it results from a failure in what is usually a normal interaction between infants and caregivers.
Effects of SBS are thought to be diffuse axonal injury, oxygen deprivation and swelling of the brain, which can raise pressure inside the skull and damage delicate brain tissue, although witnessed shaking events have not led to such injuries. Direct injuries include skull fractures, cortical contusions, diffuse axonal injuries, and hemorrhages. Indirect injuries includes brain edema and herniation.
Traumatic shaking occurs when a child is shaken in such a way that its head is flung backwards and forwards. This swift movement resulted in collision of brain to the skull, potentially tearing blood vessels and leading to bleeding around the brain, resulting in the formation of hematoma. As the hematoma enlarges, it can increase pressure within the skull, causing further injury to the brain. Then, in 1971, Guthkelch, a neurosurgeon, hypothesized that such shaking can result in a subdural hematoma, in the absence of any detectable external signs of injury to the skull. The article describes two cases in which the parents admitted that for various reasons they had shaken the child before it became ill. Moreover, one of the babies had retinal hemorrhages. The association between traumatic shaking, subdural hematoma and retinal hemorrhages was described in 1972 and referred to as whiplash shaken infant syndrome. The injuries were believed to occur because shaking the child subjected the head to acceleration–deceleration and rotational forces. However, in the 50 years since that time, no scientifically reliable evidence has been found to support this hypothesis.
Injuries The mechanical basis for SBS comes from a combination of babies having weaker neck muscles and larger heads. For example, shaking the baby can lead to veins and nerves stretching and shearing due to the head extending beyond what the baby's neck can support. Other types of injuries that can occur when shaking a baby, with or without the sudden deceleration of the head, are the following:
Subdural hematoma, a collection of blood between the brain's surface and the dura, due to overstretching of the veins connecting the brain to the dura, leading to tears and bleeding. Subarachnoid hemorrhage, bleeding between the brain and arachnoid Direct brain trauma, due to the brain striking the inner surfaces of the skull. Eye injury, retinal hemorrhage caused by to and from oscillation of the lens Skeletal injury, posterior rib fracture caused by squeezing the chest as the child is tightly gripped.
Signs and symptoms of SBS