The term abusive head trauma (AHT) is used to describe the spectrum of injuries that can arise when a caregiver shakes, throws, strikes, or otherwise injures a child resulting in skull, brain, and possibly spinal cord injury. Although children of any age may be affected, typically infants and young children are at highest risk, with most cases occurring in infants less than 1 year of age with a peak incidence noted in the first few months of life. The spectrum of injury ranges from mild to fatal, with approximately 15% to 23% of children dying from their injuries.¹ The majority of children who survive have permanent disability, which may include developmental delay or intellectual disability, blindness, seizure disorder, cerebral palsy, and feeding or respiratory issues.

The nomenclature of this entity has evolved as researchers have developed a deeper understanding of the mechanisms and pathology related to AHT. This understanding is informed not only by clinical and radiologic studies and pathologic assessment of injuries, but also by direct confessions of perpetrators. Dr. John Caffey initially noted a correlation between long bone fractures and subdural hemorrhage in 1946,² and developed the language of “shaken baby/shaken whiplash syndrome” when he published a case series of these children in 1972.³ (This phenomenon was also noted by AK Guthkelch in 1971.⁴) In 1987, Duhaime and colleagues ⁵ proposed that fatal and more severe cases of inflicted brain injury were likely to involve not only shaking but also blunt force impact, leading some to coin the term “shaken impact syndrome.” In 2009, the American Academy of Pediatrics⁶ joined many experts in supporting the term “Abusive Head Trauma,” a designation which encompasses not only injury from shaking but injuries which may be sustained when a child suffers blunt trauma or crushing injury.

The incidence of AHT is estimated to be between 24 and 34 cases per 100,000 children less than 1 year of age; however, it is likely that this is an underestimate due to unrecognized cases of abuse.⁷ Milder cases may be missed if parents fail to bring children for evaluation, and more severe cases may not be recognized, but rather mistaken for meningitis or seizure disorder, accidental injury, viral gastroenteritis, or other medical disorders. The likelihood of a misdiagnosis appears to be higher if patients have mild injury or if parents are judged by providers to be “low risk”—i.e. married, white, and economically stable.⁸ Boys appear to be victimized at a slightly higher rate than girls. Male perpetrators are more common than female, with fathers, stepfathers, and boyfriends making up 60% of offenders.⁹

Brain injury seen in AHT is caused by a cascade of events. Depending on the mechanism of injury, there often is direct trauma to the brain parenchyma during violent and repetitive shaking or during the rapid acceleration/deceleration event which occurs when a child is thrown down. There may be shearing injuries, which develop as brain tissues of different densities move at different speeds. In addition, children may experience periods of apnea (possibly related to brainstem injury) contributing to poor oxygenation of parenchymal tissue. Brain edema may lead to midline shift, causing damage to the opposite hemisphere of the brain as well as possible herniation of brain tissue. Not only does this brain edema lead to compression of smaller blood vessels which provide oxygen and nutrients to brain tissue, but these shifts of brain tissue within the cranial vault may also kink or compress vessels which supply vital territories of brain tissue. As neurons die, they release excitatory amines and other chemicals, which lead to further neurologic damage.¹⁰

Children with AHT present with a spectrum of injuries ranging from mild to severe. Victims with mild injury might present with poor feeding, vomiting, or irritability, and may be misdiagnosed as colic or gastroenteritis. There is not always bruising or other external signs of trauma. Sometimes, caregivers do not seek care for days or weeks, and symptoms may resolve without the true cause being identified. Because presenting symptoms in mild cases can be non-specific, it is important to have a high index of suspicion when treating any young child with unexplained or repeated symptoms of vomiting, irritability, lethargy, or apnea, so as to prevent discharging patients home who may be subject to more severe abuse. A large number of patients in whom the diagnosis is missed are reinjured, sometimes more severely.⁸

More extensive injury results in clear and immediate symptoms of lethargy, apnea, seizure, and cardiopulmonary instability. These gravely injured children suffer progressive worsening of symptoms over the 24 to 48 hours following their injuries, with increasing nervous system dysfunction, which may lead to coma and death.

The mechanisms causing these injuries often lead to findings which are helpful in identifying AHT. In shaking injuries, subdural hemorrhages (usually not clinically significant) are common due to torn bridging veins; subarachnoid hemorrhage may also be present. Blunt force trauma may lead to skull fracture, and other forms of physical abuse may create additional fractures of long bones or ribs. Retinal hemorrhages are present in approximately 75% of cases, and may be unilateral or bilateral.¹¹ These retinal hemorrhages are usually in multiple layers of the retina, extend to the periphery of the retina, and are numerous. The retinal layers may also be split, leading to retinoschisis or retinal folds, a highly concerning and specific finding.

The timing of injury can be difficult to determine in children who do not sustain severe injuries; however, interviews with confessed perpetrators indicate that the onset of symptoms occurs immediately after the shaking event.⁹ An accurate history of when the child was last seen behaving normally is often the most helpful clue to determine when the injury may have occurred.

It is critical to consider other potential causes for a child’s injuries due to the huge emotional and legal impact for the caregivers of a child diagnosed with AHT. Although some of the possible medical etiologies for a child’s presentation may seem very unlikely, surprisingly, these conditions will surface as legitimate explanations for the child’s symptoms as the case moves forward in the legal system. Therefore it is important to carefully consider alternative diagnoses and document the systematic evaluation and rationale for their exclusion as a likely cause for the child’s condition.

The birth process may lead to small subdural hemorrhages (SDH) or skull fractures. Most birth-related SDH are supratentorial or in the posterior fossa. These hemorrhages are usually small and clinically insignificant; most resolve within 1 to 2 weeks, although some may be detectable within 3 months of birth.¹² More significant intracranial injury generally results in symptoms that occur within the first 36 hours of life, and is therefore detected before or shortly after newborns are discharged home. Retinal hemorrhages can also result from birth. These are most commonly associated with instrumented or vaginal delivery (20%–70%), although they can occur with caesarian sections as well (1%–12%). These retinal hemorrhages are usually not associated with intracranial injury, and the vast majority resolve within 1 to 2 weeks, although residual discrete hemorrhages may persist up to 4 to 8 weeks in very rare cases.^{13, 14}

Accidental head trauma can result in some of the findings seen in AHT. Falls from significant heights and accidents that involve a parent, a car seat, or a walker that fall with the child have a greater momentum and may include not only angular but rotational forces that can lead to greater injury. However, a fall from a modest height (e.g. bed or changing table) rarely results in significant brain injury and does not cause widespread retinal hemorrhage.¹³ Children with benign extra-axial fluid collections of infancy may be at increased risk of sustaining intracranial hemorrhage with minor trauma; however, severe brain injury and retinal hemorrhage are generally not seen in these cases.