Serious injuries that result in the death or debilitation of infants or young children are seldom the result of accidents. It is estimated that 95% of severe intracranial injuries and 64% of all head injuries in children 1 year of age or younger are caused by violence inflicted by parents or caretakers [10]. By contrast, the incidence of infant death by accidental fall or drop from low height (less than 4 feet) is less than 0.5 in 1 million [20].

Though widely known today as shaken baby syndrome (SBS), it is important for healthcare professionals to embrace the all-inclusive medical terminology pediatric abusive head trauma (AHT), not to detract from shaking as a mechanism of AHT, but to acknowledge the various mechanisms of deliberate injury to infants and children [1]. AHT is a spectrum, ranging from mild injury due to sub-lethal abuse, which can cause lethargy, irritability, poor feeding, and/or vomiting occurring for days or weeks, to the most severe injury leading to coma and/or death [1]. In fact, pediatric AHT is the leading cause of death and debilitation in children among all forms of physical abuse [2]. The symptoms and conditions associated with AHT have been found in children up to 7 years of age but occur most commonly between the ages of 2 and 9 months, coinciding closely with the peak of infant crying [38,40,70]. The great tragedy is that AHT is thought to be highly preventable with well implemented parental education programs and access to support networks and services.

The abusive episode leading to head trauma almost always begins with a frustrated, stressed, or psychotic parent or caretaker being unable to calm a crying infant and acting in an impulsive and violent manner in an effort to silence them. Toddlers, on the other hand, often are abused for being "difficult" as well as for crying. Environmental risk factors for abuse include young parents, substance-addicted parents, low socioeconomic status, lack of family support, mental illness, and parental history of being abused as a child (i.e., additional stressors, inadequate coping mechanisms). Rates of AHT do not differ significantly among different racial/ethnic groups in the United States [49].

As with other forms of child abuse, poor economic stability and low income level seem to be key risk factors for AHT, although children in high-income households are not immune to abuse [11]. Child abuse in general has been found to increase as the economy worsens and access to social services decreases. One study in Pennsylvania, a state with a moderate incidence of AHT cases, reported nearly 10 cases of AHT per month during the recession of 2007–2009, up from about 6 cases per month before the recession [11]. The stress of losing a job and becoming the full-time caretaker of the child has been suggested as a contributing factor, and this was observed during the 2007–2009 recession in urban centers throughout the United States [15]. A separate study in Pennsylvania found that a very slight decrease in AHT incidence occurred during the COVID-19 pandemic lockdowns of 2020; however, the AHT mortality rate was 4.8 times higher during this time [75]. Both incidence and mortality rates returned to mean levels shortly after lockdowns eased.

Because the goal of this type of abuse is usually to stop the child from crying or otherwise aggravating the caretaker, the end result is that the sustained injuries are typically of a magnitude that causes the infant or toddler to lose consciousness for an extended period of time. This is often the presenting condition.

Aside from being comatose, a pediatric patient with traumatic head injuries of abusive origin may be convulsing, have altered consciousness, have impaired ability to suck or swallow, and be unable to track with eye movements, smile, or vocalize [1]. Skin or lips with a blue hue and lethargic eyes are signs of AHT. However, in many cases there may not be any physical clues to assist the assessment.

Severe rapid acceleration/deceleration has been found to cause rotational forces that generally result in traumatic diffuse axonal injury (DAI), which is most often seen in motor vehicle accidents in adults and AHT in pediatric patients [16]. With this injury, axons, the part of a neuron that makes contact with other neurons or cells, are stretched or torn from their connections. The damage process usually involves the brain's denser grey matter sliding over and tearing from the lighter density white matter, due to sudden deceleration, or white matter shearing from the cerebral cortex. While it was once thought that the shearing of axons themselves was the major factor in DAI, it is now understood that a biochemical cascade, involving calcium and sodium influx to the damaged axons, is responsible for the majority of post-injury cell death, localized edema, and general brain swelling [8]. Often there is secondary injury to the corpus callosum, and in rare instances, there is bleeding within the brain [18]. DAI leads to a loss of consciousness, ranging from hours to months, with upwards of 90% of cases resulting in permanent coma or death [3].

Another classic injury associated with AHT is subdural hemorrhage leading to acute subdural hematoma. When small bridging blood vessels between the dura and the brain surface are torn, mainly due to rotational forces or blunt trauma, blood begins to leak, pool, and congeal between the dura and arachnoid layers. Subdural hemorrhaging is usually venous in origin and is the most common type of intracranial hemorrhage in children. Symptoms of acute subdural hematoma in infants and toddlers include [9]:

Retinal hemorrhages are seen in 70% to 90% of AHT cases, with two-thirds of AHT patients having hemorrhages too numerous to count [1,18,21]. Although retinal hemorrhages can develop for many reasons (e.g., hypoxia, increased intrathoracic pressure, increased intracranial pressure, anemia), the repeated acceleration/deceleration forces of AHT are the usual cause in infants and children when no other plausible explanation exists [21]. Hemorrhages may be viewed through an indirect ophthalmoscopy by dilating the pupils or by the natural dilation effect resulting from injuries; use of a direct ophthalmoscope might be insufficient [21]. A long-term effect can be visual impairment, though this can possibly be attributed to direct injury of visual centers in the brain.

Fractures that result from abuse might be found on the child's skull, spine, ribs, hands, feet, nose, or any facial structure. These may be multiple or spiral fractures at various stages of healing. As discussed, mechanisms of injury that cause AHT, especially injuries from shaking, can cause multiple long-bone end fractures. It is recommended that certain high-risk groups with normal neurologic statuses, especially patients younger than 1 year of age, be selected for radiologic imaging of the head and a complete skeletal survey when no reasonable explanation of injuries exists. This includes those with rib fractures, multiple fractures, or facial injury [34]. This is because skeletal survey alone can miss more than 25% of cases of abusive head injury [34]. One study found that up to 30% of AHT is initially undiagnosed, and mean time to diagnosis is seven days, having potentially deadly consequences [7].

The decision of whether or not to report suspected abuse is ethically challenging. Although healthcare professionals are ethically and legally obligated to report suspected child abuse, suspicion of abuse is somewhat of a judgment call, and certain biases may influence the decision to report. A 2008 prospective observational study found that clinicians did not report 27% of injuries considered "likely or very likely caused by child abuse" and 76% of injuries considered "possibly caused by child abuse" [23]. However, patients who had an injury that was not a laceration, who had more than one family risk factor, who had a serious injury, who had a child risk factor other than an inconsistent injury, who were black, or who were unfamiliar to the clinician were more likely to be reported. The AAP makes several useful recommendations regarding the diagnosis and reporting of AHT [1]:

There are multiple studies documenting the success of infant shaking prevention programs, including the "Love Me…Never Shake Me" program in Ohio and "The Period of PURPLE Crying" program from the National Center on Shaken Baby Syndrome [41,42]. Analysis of these programs shows that information given at or shortly after birth, along with continued reminders at each office visit, is the most effective in reducing traumatic abuse. Considering that most parents already know that violent infant shaking is harmful, it is perhaps important for parents to make the association between this knowledge and their own infant and for parents to learn the particulars about self-care along with information about normal infant behavior. Key points of the AHT education program should include [42,43,44]: