Shaken baby syndrome

Shaken baby syndrome (SBS) is a triad of medical symptoms: subdural hematoma, retinal hemorrhage, and brain swelling from which doctors, consistent with current medical understanding, infer child abuse caused by intentional shaking. In a majority of cases there is no visible sign of external trauma.

SBS is often fatal and can cause severe brain damage, resulting in lifelong disability. Estimated death rates (mortality) among infants with SBS range from 15% to 38%; the median is 20%–25%. Up to half of deaths related to child abuse are reportedly due to shaken baby syndrome. Nonfatal consequences of SBS include varying degrees of visual impairment (including blindness), motor impairment (e.g. cerebral palsy) and cognitive impairments.

Signs and symptoms
The characteristic injuries associated with SBS include retinal hemorrhages, multiple fractures of the long bones, and subdural hematomas (bleeding in the brain). These signs have evolved through the years as the accepted and recognized signs of child abuse and the shaken baby syndrome. Medical professionals strongly suspect shaking as the cause of injuries when a baby or small child presents with retinal hemorrhage, fractures, soft tissue injuries or subdural hematoma, that cannot be explained by accidental trauma or other medical conditions. About three quarters of cases involve retinal hemorrhaging. Additional effects of SBS are diffuse axonal injury, oxygen deprivation and swelling of the brain, which can raise intracranial pressure and damage delicate brain tissue. A recent study found the prevalence of retinal hemorrhages in abusive head trauma was 78%, but only 5.3% in nonabusive pediatric head trauma. Victims of SBS may display irritability, failure to thrive, alterations in eating patterns, lethargy, vomiting, seizures, bulging or tense fontanels (the soft spots on an infant's head), increased size of the head, altered breathing, and dilated pupils.

Fractures of the vertebrae, long bones, and ribs may also be associated with SBS. Dr. John Caffey reported in 1972 that metaphyseal avulsions (small fragments of bone had been torn off where the periosteum covering the bone and the cortical bone are tightly bound together) and "bones on both the proximal and distal sides of a single joint are affected, especially at the knee".

Mechanism
SBS results from rotational acceleration of the head. Rotational injury is especially damaging and likely to occur in shaking trauma. The type of injuries caused by shaking injury are usually not caused by falls and impacts from normal play, which are mostly linear forces. The type of shaking that is necessary to cause SBS is very violent and would be clearly recognizable to an observer as dangerous and potentially deadly. The mechanism of ocular abnormalities appears to be related to vitreoretinal traction, with movement of the vitreous contributing to development of the characteristic retinal hemorrhages. These ocular findings correlate well with intracranial abnormalities.

Prevention
Prevention is similar to the prevention of child abuse in general. New parents, babysitters, and other caregivers can be warned about the dangers of shaking infants. A child's crying and irritation are common triggers for the frustration that can lead to violence in the caregiver. Some experts offer caregivers strategies to cope with their own frustrations.

Diagnosis
SBS may be misdiagnosed and underdiagnosed, and caregivers may lie or be unaware of the mechanism of injury. Commonly, there are no externally visible signs of the condition,. Examination by an experienced ophthalmologist is often critical in diagnosing shaken baby syndrome, as particular forms of ocular bleeding are quite characteristic. No alternative condition mimics all of the symptoms of SBS exactly, but those that must be ruled out include hydrocephalus, sudden infant death syndrome (SIDS), seizure disorders, and infectious or congenital diseases like meningitis and metabolic disorders. CT scanning and magnetic resonance imaging are used to diagnose the condition. Conditions that may accompany SBS include bone fractures, injury to the cervical spine (in the neck), hemorrhaging of the retina (in the eye), cerebral hemorrhage or atrophy, hydrocephalus, and papilledema (swelling of the optic disc).

Treatment
Treatment involves monitoring of intracranial pressure (the pressure within the skull), draining of fluid from the cerebral ventricles, and, if an intracranial hematoma is present, draining of the hematoma.

Prognosis
Prognosis depends on severity and can range from total recovery to severe disability to death when the injury is severe. One third of these patients die, one third survives with a major neurological condition, and only one third survives in good condition. The most frequent neurological impairments are learning disabilities, seizure disorders, speech disabilities, hydrocephalus, cerebral palsy, and visual disorders.

Epidemiology
Small children are at particularly high risk for the abuse that causes SBS given the large difference in size between the small child and an adult. SBS usually occurs in children under the age of two but may occur in those up to age five.

Risk factors
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 financial troubles, are other risk factors for aggression and impulsiveness in caregivers. Both males and females can inflict SBS, but the abusers are more often male. Although it had been previously speculated that SBS was an isolated event, a history of prior child abuse is a common finding in cases of SBS. In an estimated 33–40% of cases, evidence of prior head injuries, such as old intracranial bleeds, is present.

History
In 1946, the concept of SBS and the term "whiplash shaken infant syndrome" was introduced by Dr. John Caffey, a pediatric radiologist. The term described a set of symptoms found with little or no external evidence of head trauma, including retinal hemorrhages and intracranial hemorrhages with subdural or subarachnoid bleeding or both. In 1971, Dr. Norman Guthkelch proposed that whiplash injury caused subdural hemorrhage in infants by tearing the veins in the subdural space. Development of computed tomography and magnetic resonance imaging techniques in the 1970s and 1980s advanced the ability to diagnose the syndrome.

Concerns raised by SBS pioneer
Dr. Norman Guthkelch stated in 2011,"I don't think that the famous triad, however well some people think it's defined, can ever be so well-defined that you can say that and nothing else cause it — that meaning shaking." He is also concerned by the number of cases similar to one he reviewed in Arizona that he concluded that child likely died of natural causes not SBS stating, "I think I used the expression in my report, 'I wouldn't hang a cat on the evidence of shaking, as presented.' "

Legal issues
In July 2005, the Court of Appeals in the United Kingdom heard four appeals of SBS convictions: one case was dropped, the sentence was reduced for one, and two convictions were upheld. The court found that the classic triad of retinal hemorrhage, subdural hematoma, and acute encephalopathy are not 100% diagnostic of SBS and that clinical history is also important. In the Court's ruling, they upheld the clinical concept of SBS but dismissed one case and reduced another from murder to manslaughter. In their words: "Whilst a strong pointer to NAHI [non-accidental head injury] on its own we do not think it possible to find that it must automatically and necessarily lead to a diagnosis of NAHI. All the circumstances, including the clinical picture, must be taken into account."

The court invalidated a "unified hypothesis" proposed by Geddes and colleagues as an alternative mechanism for the subdural and retinal hemorrhage found in suspected cases of SBS. The unified hypothesis proposed that the hemorrhage was not caused by shearing of subdural and retinal veins but rather by cerebral hypoxia, increased intracranial pressure, and increased pressure in the brain's blood vessels. The court reported that "the unified hypothesis [could] no longer be regarded as a credible or alternative cause of the triad of injuries": subdural haemorrhage, retinal bleeding and encephalopathy due to hypoxemia (low blood oxygen) found in suspected SBS.

On January 31, 2008, the Wisconsin Court of Appeals granted Audrey A. Edmonds a new trial based on "competing credible medical opinions in determining whether there is a reasonable doubt as to Edmunds's guilt." Specifically, the appeals court found that "Edmunds presented evidence that was not discovered until after her conviction, in the form of expert medical testimony, that a significant and legitimate debate in the medical community has developed in the past ten years over whether infants can be fatally injured through shaking alone, whether an infant may suffer head trauma and yet experience a significant lucid interval prior to death, and whether other causes may mimic the symptoms traditionally viewed as indicating shaken baby or shaken impact syndrome."

The terms non-accidental trauma or "abusive head trauma" have been suggested instead of "SBS".

Vitamin C deficiency
Some authors have suggested that certain cases of suspected shaken baby syndrome may result from vitamin C deficiency. This contested hypothesis is based upon a speculated marginal, near scorbutic condition or lack of essential nutrient(s) repletion and a potential elevated histamine level. However symptoms consistent with increased histamine levels, such as low blood pressure and allergic symptoms, are not commonly associated with scurvy as clinically significant vitamin C deficiency. A literature review of this hypothesis in the journal Pediatrics International "From the available information in the literature, concluded that there was no convincing evidence to conclude that vitamin C deficiency can be considered to be a cause of shaken baby syndrome."

The proponents of such hypotheses often question the adequacy of nutrient tissue levels, especially vitamin C, for those children currently or recently ill, bacterial infections, those with higher individual requirements, those suffering from environmental challenges (e.g. allergies), and perhaps transient vaccination-related stresses. Given that patients presenting with suspected SBS would constitute only the most severely affected group of children with nutritionally deficiencies, one would expect a larger number of individuals seen with milder symptoms. At the time of this writing, infantile scurvy in the United states is practically nonexistent. No cases of scurvy mimicking SBS or Sudden Infant Death Syndrome have been reported, and scurvy typically occurs later in infancy, rarely causes death or intracranial bleeding, and is accompanied by other changes of the bones and skin and invariably an unusually deficient dietary history.

Gestational problems
Gestational problems affecting both mother and fetus, the birthing process, prematurity and nutritional deficits can accelerate skeletal and hemorrhagic pathologies that can also mimic SBS, even before birth. Because the age of suspected SBS victims is usually older than those patients suffering from birth-related problems, the distinction is usually not problematic.

Diffuse injury
A 2001 study reported that the predominant histological abnormality in cases of inflicted head injury in the very young is diffuse hypoxic brain damage, not DAI, and suggested two possible explanations: either the unmyelinated axon of the immature cerebral hemispheres is relatively resistant to traumatic damage, or in shaking-type injuries the brain is not exposed to the forces necessary to produce DAI.

Force
There has been controversy regarding the amount of force required to produce the brain damage seen in shaken baby syndrome. A biomechanical experiment in 2005 demonstrated that "forceful shaking can severely injure or kill an infant, this is because the cervical spine would be severely injured and not because subdural hematomas would be caused by high head rotational accelerations... an infant head subjected to the levels of rotational velocity and acceleration called for in the SBS literature, would experience forces on the infant neck far exceeding the limits for structural failure of the cervical spine. Furthermore, shaking cervical spine injury can occur at much lower levels of head velocity and acceleration than those reported for SBS." A detailed explanation of the calculations was provided in a "Letter To The Editors" in February 2006.

The BBC has made a documentary in 3 parts that covers arguments for and against the diagnosis of SBS.