Child abuse: Epidemiology, mechanisms, and types of abusive head trauma in infants and children

INTRODUCTION — The epidemiology, mechanisms, and types of head injury found in abused children are reviewed here.

The clinical features, evaluation, and diagnosis of abusive head trauma in infants and children, including ophthalmologic aspects, and the management of suspected child abuse are discussed separately. (See "Child abuse: Evaluation and diagnosis of abusive head trauma in infants and children" and "Child abuse: Eye findings in children with abusive head trauma (AHT)" and "Physical child abuse: Diagnostic evaluation and management".)

DEFINITIONS — Abusive head trauma (AHT) includes inflicted cranial, cerebral, and spinal injuries resulting from blunt force trauma, shaking, or a combination of these and other forces [1-3]. The resultant brain injury may be primary or secondary. The classic injury pattern that is associated with shaking includes diffuse unilateral or bilateral subdural hemorrhage, diffuse multilayered retinal hemorrhages, and diffuse brain injury with or without additional extracranial injuries. This pattern has been previously referred to as the "shaken baby syndrome" and "shaken/impact syndrome" [4,5]. The absence of a history of trauma and a paucity of external manifestations of injury can make recognition of the inflicted nature of these injuries difficult. The AAP has recommended that the term "shaken baby syndrome" be replaced in medical records with the broader term "abusive head trauma", which allows for consideration of multiple mechanisms of injury in any child [2]. Generic terms, such as "head injury", also serve to distinguish the diagnosis of injury from the investigation of how the injury occurred [2,6,7].

The mechanism of brain injury is only one factor that must be considered in making the diagnosis of abusive injury. The significance of the diagnosis (with regard to child protection and criminal prosecution) may be similar, regardless of whether injury resulted from direct blows or from shaking [8]. In addition, much of the evidence to support the mechanism of injuries that result from shaking is retrospective and indirect. (See 'Mechanisms of injury' below and "Child abuse: Evaluation and diagnosis of abusive head trauma in infants and children", section on 'Diagnosis'.)

EPIDEMIOLOGY — Child abuse occurs most often among children less than four years of age [9]. In one population-based study, the most common mechanism of injury for infants three to five months of age was battering [10]. Among young children, head injury, in particular, is often inflicted. This is illustrated in the following reports:

●In several case series describing children who were admitted to the hospital with head injury, between 21 and 33 percent of injuries were inflicted [11-13].

●In a retrospective report, injury was inflicted in 53 percent of children two years of age or younger with traumatic brain injuries, who were admitted to a pediatric intensive care unit, or died [14].

The incidence of abusive head trauma (AHT) among children is similar in the United States and Europe. In a population-based study conducted in the United States, the incidence of AHT among children younger than two years was 17 per 100,000 person-years (95% CI 13-21 per 100,000 person-years); the incidence was greater in the first than in the second year of life (30 versus 4 per 100,000 person-years) [14-16]. Population-based studies from Europe report similar incidences of AHT in the first year of life (25 and 29 per 100,000 person-years) [17,18].

Nearly one-half of all fatalities from child abuse occur among children younger than 12 months of age [9]. AHT is among the leading causes of child maltreatment fatalities, and there is some evidence that fatality rates have decreased [19]. Most fatal head injuries in children less than two years old are secondary to abuse [20]. Head-injured infants frequently present with nonspecific clinical features and no history of trauma. As a result, as many as 30 percent of children with inflicted head injuries may be misdiagnosed at the initial evaluation [21].

Early identification of AHT can be lifesaving. In one retrospective review describing missed cases of abusive head injury, four of five deaths may have been prevented if the inflicted mechanisms had been recognized during prior medical evaluations for symptoms related to undisclosed head trauma [21]. The probability of AHT increases with each associated high risk physical finding as discussed separately [22]. (See "Child abuse: Evaluation and diagnosis of abusive head trauma in infants and children", section on 'Children with intracranial injury'.)

Age — Most cases of AHT occur during the first year of life [14,23-27]. In three studies comparing children with AHT to those with an unintentional mechanism, the median age of those who had been abused was four months [13,14,28]. Children with unintentional head injury were significantly older. Abusive head injury in older children has been reported [29,30].

Prior history of abuse — Identified victims may have clinical evidence of previous abuse at the time of diagnosis and others may have evidence in past records or by family history of previous injury. In one large series describing children with inflicted head injury, a history and/or clinical evidence of previous maltreatment was noted in 60 percent of cases [23]. Child welfare agencies had been previously involved with 22 percent of families. In another study of AHT involving perpetrator confessions, repeated episodes of shaking were reported in 55 percent of cases and ranged from 2 to 30 events [1]. Children diagnosed with AHT often have a history of prior red flag injuries (visible skin or mouth injuries or previous fractures) (table 1) that are known by the parents/primary caregivers and at times, by medical providers [31].

Limited evidence suggests that it is not unusual for clinicians to initially misinterpret nonspecific signs and symptoms of AHT (as an example, vomiting or irritability), leading to a delay in diagnosis. In one retrospective series, the diagnosis of AHT was missed in 31 percent of children [21]. The most frequent diagnoses applied to children with missed AHT included viral gastroenteritis or influenza, accidental head injury, and "rule out sepsis." Of those whose injuries were not recognized as inflicted, 28 percent were reinjured before the correct diagnosis was made. Four of these children died as the result of their subsequent injuries.

Perpetrators — The perpetrators of AHT are usually male and typically the father of the infant [23,32-34]. In one retrospective study, the perpetrator was identified in 240 cases (66 percent); in decreasing order of frequency, the perpetrator was the father (50 percent), stepfather or male partner of the mother (20 percent), and mother (12 percent) [23]. Similar results were found in another review of 151 cases; in addition, female babysitters were identified as perpetrators in 17 percent of cases [32].

Risk factors — Risk factors associated with child abuse generally include young and/or single parents/primary caregiver, those with lower levels of education; unstable family situations; stress factors within the family including perceived financial, food and/or housing stresses; domestic violence, alcohol/drug abuse, and parental depression. One study of household composition in child maltreatment fatalities showed that the increased risk in single-parent households was present only when other unrelated adults also resided in the home, particularly stepfathers and maternal boyfriends [35]. (See "Physical child abuse: Recognition", section on 'Epidemiology'.)

Observational studies have identified the following risk factors as being associated specifically with AHT:

●Infant factors

•Perinatal illness (prematurity, obstructed labor and/or hospitalization after birth) and major congenital anomalies [36,37].

•Incessant crying is a common trigger for inflicted injury [1,38-40]. Thus, "colicky" babies or those infants whose caregivers have limited ability to tolerate crying may be at increased risk for AHT. In one study, perpetrators often reported shaking the infant as an effective way to make the baby stop crying [1].

•Male sex [37].

●Family risk factors

•Antecedents of familial dysfunction (ie, drug or alcohol abuse, history of violence, police involvement, or a psychiatric illness) [36,41]

•Young maternal age [37]

•Family disruption and separation [34], including maternal military service [37]

•Prior history of abuse of the index child or other family members [34]

In addition, economic factors at a population level may have an impact on the frequency of AHT. As an example, an increase in AHT coincident with the economic recession beginning in 2007 was observed in a trauma database analysis. The mean monthly incidence of AHT increased by 101 percent from the pre-recession to the recession period, while the rate of unintentional head trauma decreased by 3.5 percent over the same time period [42,43]. Conversely, rates of AHT declined across 49 United States children's hospitals during the coronavirus 2019 pandemic [44].

AHT primarily occurs in private homes and uncommonly occurs in day care centers [45].

MECHANISMS OF INJURY — Children with abusive head trauma (AHT) may have severe brain injury, often in the absence of a history of significant trauma and with minimal or no signs of external injury [2,46]. In comparison, patients with unintentional mechanisms more commonly present with a history of trauma and external signs of injury around the head [12,47]. However, on occasion, infants and young toddlers with accidental blunt head trauma can have intracranial bleeding without evidence of skull or soft tissue injury [48]. (See "Child abuse: Evaluation and diagnosis of abusive head trauma in infants and children", section on 'Clinical features'.)

Specific injuries that are associated with abuse include subdural hemorrhage (typically diffuse, thin-layered, and often along the falx and/or over the cerebral convexities), diffuse multilayered retinal hemorrhages, and diffuse brain injury. Mechanisms involving shaking and/or impact have been proposed to explain this pattern [1,4,36,49]. Spinal cord injuries, as well as ligamentous, vertebral and paraspinal soft tissue injuries may also be seen in AHT [50,51]. (See 'Spinal and paraspinal injuries' below.)

Susceptibility — Evidence suggests that the brains of infants are more vulnerable to injury as the result of angular (rotational) deceleration than are those of adults [52]. In addition, experimental evidence from studies with neonatal piglets suggests that brain injury increases with repetitive rotational events in comparison to a single event [53]. Particular features that may contribute to this susceptibility include the following [4,24,54]:

●The base of the infant skull is relatively flat, permitting the brain to move more readily in response to deceleration forces.

●The infant skull is thin and pliable. Because of this, forces are transferred more effectively across the shallow subarachnoid space to the brain.

●The head of an infant is relatively large, heavy, and unstable. The brain of an average two-year-old child is approximately 75 percent the weight of an average adult brain. The large head and weak neck musculature (particularly prominent in young infants) permit greater movement when the head is acted upon by acceleration-deceleration force.

●Infants and young children have relatively soft brains with high-water content. In addition, the newborn central nervous system is not completely myelinated and the infant is less able to autoregulate blood flow after injury than older children [55,56]. These features make the developing brain more susceptible to injury.

Primary injury — In general, the types and severity of head injuries sustained by an infant or child are related to the relative contributions of rotational and translational forces, and it should be noted that most head injuries result from combinations of these forces. Evidence from biomechanical models is controversial. Experimental models suggest that angular deceleration forces (that cause rotation of the head on its axis, with differential movement of the skull/dura and intracranial contents) cause primary parenchymal injury, including traumatic axonal injury [57]. Subdural and retinal hemorrhages have been difficult to model in the biomechanical lab. Biomechanical forces have been shown to be greater with shaking and impact than with shaking alone [24].

In comparison with shaking, injury from a short fall (ie, from a changing table or bed to the floor) is primarily the result of translational deceleration (movement of the head in a straight line) and cranial impact [58]. Injuries from this unintentional mechanism are typically focal and mild, although rare exceptions exist [59,60]. As an example, multifocal hypodensities on computed tomography (CT) occurred within one hour after a well-documented fall from a stool in a two-year-old child who developed rapid onset of coma after the injury and subsequently died [61].

Secondary injury — In addition to direct injury from traumatic forces, the brain can also be injured by secondary hypoxia, ischemia, and/or unmet metabolic needs [62,63]. Both clinical and neuropathologic studies support the importance of secondary hypoxic-ischemic injury in the pathogenesis of cerebral injury in abused children [50,62,64,65]. This may be the result of various mechanisms, including central apnea from injury to the brainstem and cervical spinal cord during shaking, prolonged seizure activity, aspiration from loss of airway protective reflexes, changes in cerebral blood flow, and other contributors. Hypoxic ischemic cerebral injury occurs significantly more frequently following AHT than after serious unintentional head trauma [62]. (See "Severe traumatic brain injury (TBI) in children: Initial evaluation and management", section on 'Pathophysiology' and "Child abuse: Evaluation and diagnosis of abusive head trauma in infants and children", section on 'Unstable patients'.)

The minimal amount of force required to produce the pattern typically associated with inflicted injury (diffuse subdural hemorrhage, extensive retinal hemorrhages, and diffuse brain damage) is unknown and obvious ethical considerations preclude experimental studies to address this question. Experts generally agree, however, that normal handling and minor trauma do not cause this pattern of serious injury, and that significant forces are involved [6,66]. Repeated use of violent forces have been confirmed by perpetrator confessions of AHT [1].

TYPES OF INJURY — Injuries associated with inflicted head trauma in infants and children include retinal hemorrhages, intracranial bleeding, skull fractures, skeletal fractures, bruising, and other injuries [2]. Some or all of these injures may be present in any given child. The probability of an abusive mechanism of injury increases with increasing combinations of these associated clinical findings [22].

Retinal hemorrhages — Retinal hemorrhages are frequently noted in children with abusive head trauma (AHT), including fatal cases [2]. In comparison, they occur much less commonly among those with unintentional head injury [46]. As an example, in a review of the literature from 1950 to 2009, the odds ratio of AHT in a child with head injury and retinal hemorrhages was 14.7 with a probability of 91 percent [67]. Retinal hemorrhages associated with AHT are characteristically numerous, involve multiple layers of the retina, extend beyond the posterior pole, and sometimes include the peripheral retina (picture 1 and figure 1 and figure 2) [68]. Less severe retinal hemorrhages are less specific for abuse and are occasionally identified after unintentional injury and in a variety of other medical conditions. Retinal hemorrhages as a result of AHT and the differential diagnosis of retinal hemorrhages are discussed in greater detail separately. (See "Child abuse: Eye findings in children with abusive head trauma (AHT)", section on 'Retinal hemorrhages' and "Child abuse: Eye findings in children with abusive head trauma (AHT)", section on 'Differential diagnosis'.)

Intracranial bleeding — Intracranial hemorrhage (ICH) is one of the characteristic features of abusive head trauma (AHT) and may include subdural hemorrhage (SDH), intraparenchymal bleeding, subarachnoid hemorrhage (SAH), epidural hemorrhage (EDH), or a combination of these. Concomitant skull fracture may or may not be present.

Significant intracranial injury rarely occurs as the result of low-impact trauma, such as a short vertical fall. Several studies of short falls in infants and young children confirm the rarity of serious intracranial injury [69-71]. According to a review of published data, including literature reviews and multiple databases, the annual risk of death from short falls involving infants and young children is less than 0.48 deaths per one million young children per year [72]. On rare occasions, a short fall can result in serious or even fatal injury, requiring careful inquiry and investigation in all such cases.

One retrospective series evaluated the injuries sustained by 167 infants (less than 10 months of age) in short vertical falls (4 feet or less) [73]. The following findings were noted:

●The majority of patients (85 percent) had no or only minor injuries (without fracture or loss of consciousness).

●Twelve children (7 percent) had skull fractures, all of which were isolated and linear.

●Two infants who had intracranial bleeding were later confirmed to have inflicted injuries.

Subdural hemorrhage — SDH is an unusual accidental injury in children, except when significant forces are involved (eg, a motor vehicle collision or fall from significant height) or the SDH is small and localized to the site of cranial impact [11,74-79]. They are occasionally identified after occipital impacts [59]. Subdural hemorrhages are significantly associated with AHT, occurring almost three times more frequently in abused children than patients with serious unintentional head trauma (image 1 and image 2). Additional characteristics of subdural hemorrhages seen in inflicted head trauma include multiple hemorrhages with differing density or susceptibility on imaging, interhemispheric or posterior location, and extension over the convexity of the brain. (See "Child abuse: Evaluation and diagnosis of abusive head trauma in infants and children", section on 'Unstable patients'.)

Clinically silent SDH may occur in term neonates as the result of birth trauma. In a prospective study in which 111 newborn infants underwent magnetic resonance imaging (MRI) within 48 hours of birth, subdural hemorrhage was present in nine (8 percent) (three vaginal deliveries, five forceps deliveries, and one traumatic vacuum-assisted delivery) [80]. None of the infants required intervention, and SDH was resolved in all cases by the time of follow-up MRI at four weeks of age. Another study yielded a 26 percent rate of intracranial hemorrhage among 88 neonates undergoing MRI after vaginal delivery [81]. Of the 17 infants with intracranial hemorrhage, 16 had SDH. Thus, limited evidence suggests that the majority of SDHs related to birth resolve within a few weeks, but this does not exclude the possibility of progression to chronic subdural hemorrhage in some cases. Additional data is necessary to clarify this issue.

In most cases of AHT, the subdural hemorrhage is eventually resorbed, but in some, the hyperdense blood seen on CT evolves into a hypodense fluid collection, which may gradually increase in size. The time required for this evolution varies from a few days to weeks [82]. A sizable proportion of abused infants with head injury present with chronic subdural collections with or without additional acute or healing injuries. Such findings raise the possibility of prior episodes of abuse, which should prompt additional investigation [75,82,83].

Epidural hemorrhage — Epidural hemorrhage (EDH) denotes bleeding into the space between the dura and the inner surface of the skull (image 3). EDH occurs significantly more frequently following unintentional head trauma than after AHT. Falls are the typical mechanism of injury for EDH in children with unintentional head injury and the hemorrhages that result are typically small (1 cm thick and isolated) and without associated injuries [75,84]. Of note, retinal hemorrhages can occur in conjunction with epidural hemorrhage. As an example, sparse retinal hemorrhages were described in five infants with epidural hematoma that required evacuation [85]. None of these patients were determined to have been abused by the institutional child protection team. (See "Child abuse: Evaluation and diagnosis of abusive head trauma in infants and children", section on 'Unstable patients'.)

Subarachnoid hemorrhage — Although subarachnoid hemorrhage (SAH) is present in nearly all fatal cases of inflicted head trauma, it may be difficult to detect when small in size or located on the interhemispheric surfaces of the brain and does not occur more frequently after inflicted head trauma than following unintentional head trauma. (See "Child abuse: Evaluation and diagnosis of abusive head trauma in infants and children", section on 'Unstable patients'.)

Parenchymal injuries — The type and severity of parenchymal injury in AHT varies with the mechanism of injury and magnitude of forces involved. Parenchymal damage can occur as the result of contact forces, inertial forces, and/or as a consequence of secondary brain injury from global hypoxia/ischemia.

Contact forces may cause small cerebral contusions from deformation of the overlying skull. Massive contact forces may cause extensive underlying cerebral contusion and laceration. Crush injuries often lead to parenchymal contusions and lacerations [86]. Other parenchymal changes associated with contact forces may result from compression by an enlarging extra-axial mass lesion (EDH or SDH) compromising blood flow to the underlying parenchyma and leading to focal parenchymal ischemia.

Inertial forces with angular (rotational) deceleration can cause traumatic axonal injury (either focal or diffuse), gliding contusions, and/or focal parenchymal tears. Such injuries are especially common in the subcortical white matter, corpus callosum, periventricular regions, and dorsolateral aspect of the rostral brainstem [54,58,87,88].

Global hypoxia/ischemia, as the result of AHT, can also cause parenchymal brain injury and is believed to be an important contributor to poor outcome [62]. Axonal injury from hypoxia has been noted in series of fatal inflicted neurotrauma, suggesting that local traumatic damage to the corticospinal tracts of the lower pons, medulla, and cervical spine may be responsible for the apnea, respiratory distress, and resultant hypoxia so often encountered in children with AHT [64,65,89,90]. Thus, severe AHT may cause primary damage to the brainstem, including the respiratory centers that initiate widespread secondary hypoxia, leading to global hypoxic/anoxic changes and brain swelling [90]. In one study of infants with AHT and accidental head injury, cervical ligamentous injury was positively associated with hypoxic-ischemic brain injury. The ligamentous injuries were predominantly posteriorly located, suggesting that severe neck flexion may be an important mechanism of injury [50]. Hypoxic/ischemic changes may also result from secondary hypotension, prolonged seizure activity, and other mechanisms.

Subacute and chronic parenchymal changes associated with inflicted head injury include infarction, atrophy, and encephalomalacia with ventriculomegaly [5,89,90].

Cerebral sinovenous thrombosis — Cerebral sinovenous thrombosis is uncommon in children with abusive head trauma, accounting for 7 percent of patients in one study [91]. All patients with cerebral sinovenous thrombosis in this series had other extra-cranial injuries consistent with child abuse such as fractures, cutaneous injuries, retinal hemorrhages, or abdominal injuries.

Spinal and paraspinal injuries — Infants are vulnerable to spinal injury due to developmental anatomical characteristics, including greater elasticity of the infant spine, horizontal orientation of the cervical facet joints, underdeveloped intervertebral joints, and low tone of the infant neck muscles [92].

Based upon retrospective observational studies, many victims of AHT demonstrate spinal injury, such as extra-axial hemorrhage, ligamentous injury, trauma to the paraspinal soft tissues, and/or spinal cord injury. Such injuries are reported in a significant proportion of such patients who undergo spinal MRI, although rates vary widely [50,92-95]. Spinal hemorrhage and other injuries are also found at the time of autopsy in victims of AHT [96]. Many injuries occur in the cervical region, but thoracic and lumbar injuries are also found. In some cases, spinal subdural hemorrhage is related to blood that has tracked down from the posterior fossa. The findings are not usually accompanied by clinical signs or symptoms of spinal trauma (or they are masked by altered mental status). As an example, in one study of infants with AHT and spinal neuroimaging, 44 percent were found to have subdural hemorrhages in the spine and all of these were clinically occult [97].

Infants with unintentional trauma and suspicion for spinal injury also have a high frequency of spinal injury. By contrast, the frequency of such injuries in infants with nontraumatic conditions who undergo spinal MRI is low. Thus, clinicians should have a low threshold for spinal imaging in victims of AHT and should be alert for other signs of child abuse in children who have spinal injuries without a history of trauma. (See "Child abuse: Evaluation and diagnosis of abusive head trauma in infants and children", section on 'Associated injuries'.)

Skull fractures — Skull fractures are frequently seen in children with AHT, but are also common in those with unintentional head injury. For example, in an observational study of 218 children with traumatic brain injury (54 with AHT), skull fractures were reported in 57 and 30 percent of children with unintentional head injury and AHT, respectively [78]. In a systematic review of seven studies that reported skull fractures in 520 children (predominantly infants and toddlers), the probability of abuse in children with a skull fracture was 30 percent (95% CI 19-46 percent) [98]. In children with a clear history of trauma, no extracranial injuries and no social concerns, most skull fractures are unintentional [99].

Linear, parietal skull fractures are the most common type of skull injury following both unintentional and inflicted trauma (image 4) [100-102]. Given the similar clinical features of unintentional and abusive skull fractures, these injuries should be evaluated in the context of the history that is provided by the child's caregiver(s) [99]. Abusive injury should be suspected if the history is inconsistent with the physical examination findings. If the mechanism of injury is a fall, it is important to determine the height of the fall and the type of surface of impact (eg, concrete, wood, carpet). In general, falls from two feet or less are unlikely to produce head injuries more serious than linear skull fractures [103].

Complicated skull fractures (ie, complex [eg, stellate, branching], multiple, bilateral, crossing suture lines, depressed, or diastatic) are reported by some to be suggestive of AHT. However, the specificity of complicated skull fractures as an indicator of child abuse varies as illustrated by the following studies:

●In one observational study of skull fractures in 89 children younger than two years (29 with AHT), fractures that crossed suture lines or were multiple, diastatic, growing, depressed, complex (eg, stellate, branching), or bilateral were much more common among children who were abused than those who had unintentional injuries (83 versus 22 percent) [104]. The majority of unintentionally injured children had single linear fractures (78 percent).

●Another observational study of 134 young children (39 with AHT), who in general, had injuries of minor severity, found no significant difference between abusive and unintentional trauma in the incidence of complex, diastatic, or depressed fractures (39 versus 42 percent); however, fractures that were multiple, bilateral, or crossed suture lines were significantly more common in abused children (52 versus 22 percent) [101].

●In another review of 94 children with skull fractures (26 with AHT), the parietal region was the most common fracture site in cases of abuse and unintentional injury (81 and 77 percent, respectively) [100]. Linear fractures were found in a majority (54 percent) of the abuse cases. Complicated fractures (eg, multiple, bilateral, diastatic, or depressed) were more common in the abuse than the accidental group (46 versus 26 percent). In addition, among the 14 children who sustained a complicated skull fracture after unintentional falls, six were injured in falls from relatively short heights (60 to 119 cm [two to four feet]).

●Bilateral, symmetrical parietal skull fractures were reported in a six-week old infant who had midline head impact after a short witnessed fall onto concrete; the midline impact was felt to be responsible for the bilateral fractures [105].

Taken together, these studies indicate that the clinician should suspect abuse in infants and young children with complicated skull fractures when the history of injury is absent or implausible, but should recognize that unintentional trauma may cause such injuries.

The clinical manifestations, radiologic evaluation, and management of skull fractures in children are discussed in greater detail separately. (See "Skull fractures in children: Clinical manifestations, diagnosis, and management", section on 'Clinical manifestations' and "Skull fractures in children: Clinical manifestations, diagnosis, and management", section on 'Diagnosis and radiologic evaluation' and "Skull fractures in children: Clinical manifestations, diagnosis, and management", section on 'Management'.)

Skeletal fractures — Approximately 20 to 50 percent of victims of AHT have extracranial skeletal fractures [14,23,106]. In a prospective study comparing young children with serious AHT versus unintentional head injury, the abused patients were more likely to have rib, long-bone, and metaphyseal fractures than those who had sustained accidental trauma [28]. Two types of fracture are associated with inflicted head trauma, although they are not always identified in abused infants [46]:

●Classic metaphyseal lesions of the long bones were one of the early injuries described in infants with AHT and are strongly associated with child abuse (figure 3 and image 5 and image 6). (See "Orthopedic aspects of child abuse", section on 'Location and type of fracture'.)

●Rib fractures in infants with normal bones are also strongly associated with child abuse and may occur when the torso is grasped and compressed during shaking (image 7). In one literature review where the prevalence of AHT was 47 percent, the presence of rib fractures in an infant with intracranial injury had a positive predictive value of 73 percent for AHT [107]. Inflicted rib fractures usually are nondisplaced and may involve single or multiple sequential ribs, and may occur unilaterally or bilaterally. Rib fractures are often difficult to detect clinically and radiographically when they are acute. (See "Child abuse: Evaluation and diagnosis of abusive head trauma in infants and children", section on 'Diagnosis' and "Orthopedic aspects of child abuse", section on 'Rib fractures'.)

Other orthopedic injuries associated with child abuse are discussed separately. (See "Orthopedic aspects of child abuse", section on 'Fracture patterns'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Child abuse and neglect".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topic (see "Patient education: Head injury in babies and children under 2 years (The Basics)")

SUMMARY

●Epidemiology – Abusive head trauma (AHT) is an important cause of morbidity and mortality in young children, particularly among those younger than 12 months of age. Cranial injury may be the result of direct blows or shaking (particularly of an infant), dropping, throwing the child, or a combination of mechanisms. The injury pattern that is associated with shaking includes subdural hemorrhage, retinal hemorrhage, and brain injury. (See 'Epidemiology' above.)

AHT occurs most often in the first year of life. The incidence of inflicted traumatic brain injury among children is similar in the United States and Europe. Many victims have a history of previous abuse, and the diagnosis is frequently delayed. The perpetrators of AHT are usually male and most commonly, the father of the infant. (See 'Age' above and 'Prior history of abuse' above and 'Perpetrators' above.)

●Mechanism of injury – Angular deceleration, with or without impact, results in differential movement of intracranial contents that may cause axonal injury and intracranial bleeding. The infant brain is more susceptible to this type of injury. Normal handling and minor trauma do not typically generate sufficient force to cause serious injury. (See 'Susceptibility' above and 'Primary injury' above.)

Hypoxic-ischemic injury is also an important contributor to the types of brain injury seen after AHT. (See 'Secondary injury' above.)

●Associated injuries – Injuries associated with AHT include skull (image 4), metaphyseal (image 6), and rib fractures (image 7); retinal hemorrhages (figure 2); and intracranial bleeding, especially subdural hemorrhage (image 1). (See 'Types of injury' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges V Jordan Greenbaum, MD, who contributed to earlier versions of this topic review.