Understanding Abusive Head Trauma: A Primer for the General Pediatrician

Abusive head trauma (AHT) refers to a well-recognized constellation of injuries caused by the direct application of force to an infant or young child, resulting in trauma to the head, intracranial contents, and/or neck, with potentially devastating health outcomes. Mechanisms of AHT include impulsive injurious acts, such as violent shaking and impact, often due to caregiver frustration or exhaustion. Subdural and retinal hemorrhage, and associated extracranial injury (fractures, abdominal trauma), are common. Suspected victims require laboratory/diagnostic testing and occult injury screening, as well as protective measures by investigative authorities to ensure safety. Medicolegal controversies persist around AHT diagnosis, including alternative hypotheses proffered in court by skeptics despite advances in scientific understanding, biomechanical research, neuroimaging techniques, and perpetrator confessions. Pediatricians play a key role in prevention and reduction of AHT morbidity and mortality through anticipatory guidance and caregiver education about the risks of shaking, normal infant development and behavior, and encouragement of stress reduction strategies. [Pediatr Ann. 2020;49(8):e347-e353.].

Shaken baby syndrome: what certainty do we have?

BACKGROUND

Shaken baby syndrome is a common and devastating disease in infants. In spite of its frequency, many controversies persist, regarding the pathophysiology, diagnosis, and management.

AIM OF THE STUDY

We reviewed several salient and challenging issues related to SBS, like its pathogenesis, predisposing factors, differential diagnosis, and prevention programs.

MATERIAL AND METHODS

We derive arguments from the literature and from our prospective registry of accidental and non-accidental traumas in infants.

CONCLUSIONS

Much remains to be understood in SBS, and prevention programs for this entirely man-made disaster are still in their infancy. Pediatric neurosurgeons should be involved actively in the medical management and research on SBS.

Development of a computational biomechanical infant model for the investigation of infant head injury by shaking

The inertial loading thresholds for infant head injury are of profound medico-legal and safety-engineering significance. Injurious experimentation with infants is impossible, and physical and computational biomechanical modelling has been frustrated by a paucity of paediatric biomechanical data. This study describes the development of a computational infant model (MD Adams®) by combining radiological, kinematic, mechanical modelling and literature-based data. Previous studies have suggested the neck as critical in determining inertial head loading. The biomechanical effects of varying neck stiffness parameters during simulated shakes were investigated, measuring peak translational and rotational accelerations and rotational velocities at the vertex. A neck quasi-static stiffness of 0.6 Nm/deg and lowest rate-dependent stiffness predisposed the model infant head to the highest accelerations. Plotted against scaled infant injury tolerance curves, simulations produced head accelerations commensurate with those produced during simulated physical model shaking reported in the literature. The model provides a computational platform for the exploitation of improvements in head biofidelity for investigating a wider range of injurious scenarios.

Neuropathological changes in a lamb model of non-accidental head injury (the shaken baby syndrome)

Non-accidental head injury (NAHI), also termed the "shaken baby syndrome", is a major cause of death and severe neurological dysfunction in children under three years of age, but it is debated whether shaking alone is sufficient to produce brain injury and mortality or whether an additional head impact is required. In an attempt to resolve this question, we used a lamb model of NAHI since these animals have a relatively large gyrencephalic brain and weak neck muscles resembling those of a human infant. Three anaesthetised lambs of lower body weight than others in the experimental group died unexpectedly after being shaken, proving that shaking alone can be lethal. In these lambs, axonal injury, neuronal reaction and albumin extravasation were widely distributed in the hemispheric white matter, brainstem and at the craniocervical junction, and of much greater magnitude than in higher body weight lambs which did not die. Moreover, in the eyes of these shaken lambs, there was damage to retinal inner nuclear layer neurons, mild, patchy ganglion cell axonal injury, widespread Muller glial reaction, and uveal albumin extravasation. This study proved that shaking of a subset of lambs can result in death, without an additional head impact being required.

Comparison of system identification techniques in the analysis of a phantom for studying shaken-baby syndrome

This article compares two techniques for estimating the parameters describing the motion of a phantom designed to investigate shaking baby syndrome. Parameters of a simple computational model and an impulse response function for a linear second order system were both fitted using kinematic measurements of the motion of an inverted jointed pendulum. From the two methods respectively, the rotational stiffness of the joint was calculated to be 1.396 kgm(2) s(-2) and 1.355 kgm(2) s(-2) and the damping coefficient was calculated to be 0.0142 kgm(2) s(-1) and 0.0133 kgm(2) s(-1). The parameter estimates were similar demonstrating that the two techniques were comparable. Identifying accurate parameters will allow more complex phantoms to be modeled, and will provide insight into the relationship between the shaking of the torso and the resultant head motion during shaken baby syndrome.

[Shaken baby syndrome]

Nearly all non accidental head injuries of children are shaken baby syndromes. The non accidental head trauma refers to a traumatic encephalopathy inflicted by an adult to a child. The syndrome combines subdural haematoma, retinal haemorrhages and absence of any external lesion. The mortality and morbidity rates of the SBS are high and the SBS is the main cause of death in hospitals handling child abuse. The incidence is not well-known and most probably underestimated. Numerous risk factors linked to the aggressor, to the victim and to the factual context have been identified. The diagnosis remains difficult to make, mainly due to the absence of reliable anamnesis in a majority of cases. It should be envisaged for all infants presenting unexplained acute encephalopathy. Imagery and ophthalmologic examination are the first examinations that are required to make such diagnosis. A cerebral RMI allowed for important progress both on the level of the diagnosis and the prognosis as well as on the level of the understanding of lesions. The physiopathogeny of this syndrome has considerably progressed in recent years which raise promising prospects for therapy. The treatment of babies with SBS requires highly competent teams including paediatric neurosurgeons but also teams specialised in child abuse which can quickly take care of the families. In view of the seriousness of the problem, several communication campaigns directed to young parents and the public have been organized recently in several countries among which Belgium.

Finite element model of ocular injury in abusive head trauma

PURPOSE

To develop a finite element analysis of the eye and orbit that can be subjected to virtual shaking forces.

METHODS

LS-DYNA computer software was used to design a finite element model of the human infant eye, including orbit, fat, sclera, retina, vitreous, and muscles. The orbit was modeled as a rigid solid; the sclera and retina as elastic shells; the vitreous as viscoelastic solid or Newtonian fluid; and fat as elastic or viscoelastic solid. Muscles were modeled as spring-damper systems. Orbit-fat, fat-sclera, sclera-retina, and vitreous nodes-retina interfaces were defined with the use of the tied surface-surface function in LS-DYNA. The model was subjected to angular acceleration pulses obtained from shaking tests of a biofidelic doll (Aprica 2.5 kg dummy). Parametric studies were conducted to evaluate the effect of varying the material properties of vitreous/fat on maximum stress and stress distribution.

RESULTS

With the vitreous modeled as a Newtonian fluid, the repeated acceleration-deceleration oscillatory motion characteristic of abusive head trauma (AHT) causes cumulative increases in the forces experienced at the vitreoretinal interface. Under these vitreous conditions, retinal stress maximums occur at the posterior pole and peripheral retina, where AHT retinal hemorrhage is most often found.

CONCLUSIONS

Our model offers an improvement on dummy and animal models in allowing analysis of the effect of shaking on ocular tissues. It can be used under certain material conditions to demonstrate progressive "stacking" of intraocular stresses in locations corresponding to typical AHT injury patterns, allowing a better understanding of the mechanisms of retinal hemorrhage patterns.

Non-accidental head injury in New Zealand: the outcome of referral to statutory authorities

OBJECTIVES

To describe the outcome of referral to the statutory authorities for infants under 2 years with non-accidental head injury (NAHI), and to establish whether the authorities held sufficient information to develop a risk profile for these cases.

METHODS

Retrospective review of cases admitted to hospital in Auckland, New Zealand from 1988 to 1998. Records from the hospital admission, child protective services and Police were reviewed, up to 19 years from diagnosis.

RESULTS

Of 39 infants, 33 survived to leave hospital. Documentation of risk factors was erratic, and sometimes incongruent between agencies. Inter-agency case conferences took place in 17/39 (44%). The Department of Child, Youth and Family Services (CYF) used an informal family agreement to secure safety in 15/33 survivors (45%). Family Group Conferences occurred in 17/33 (52%). Nine of 33 were placed permanently outside the home (27%), two (6%) with unrelated caregivers. Charges were laid in 18/39 cases (46%). Fifteen cases came to trial, with 14 convictions (36%). Of the survivors, 44% were later renotified to CYF. There was no obvious relationship between type of intervention and re-notification.

CONCLUSIONS

Ensuring the safety of an infant with NAHI, and identifying and taking appropriate action with regard to the offender, are complex tasks. In New Zealand, data collection is often incomplete and inter-agency practice and collaboration is variable. Although the rate of prosecution was relatively high by international standards, many children were later notified again for further concerns of abuse or neglect, suggesting that our interventions have been only partially successful.

PRACTICE IMPLICATIONS

This paper suggests that all infants admitted to hospital with non-accidental head injury should become part of a prospective inter-agency research study, using a standardised data collection instrument. This should include the systematic collection of all data known or suspected to be associated with risk of child abuse, and incorporate long-term prospective follow-up, regardless of child protective or legal outcomes. Without large numbers followed prospectively and according to sound methodology, it is difficult to prove which forms of intervention are better than others at reducing the risk of further abuse.

The physical manifestations of shaken baby syndrome

Shaken baby syndrome (SBS) is a great concern for forensic nurses. Accurate diagnosis and treatment is essential. The purpose of this report is to review the history of SBS, as well as the physical symptoms of a patient suspected of suffering from this form of abuse. Implications of SBS for the forensic nurse will be presented; this will include the education of families and caregivers and methods of prevention.

Infant brain subjected to oscillatory loading: material differentiation, properties, and interface conditions

Past research into brain injury biomechanics has focussed on short duration impulsive events as opposed to the oscillatory loadings associated with Shaken Baby Syndrome (SBS). A series of 2D finite element models of an axial slice of the infant head were created to provide qualitative information on the behaviour of the brain during shaking. The test series explored variations in subarachnoid cerebrospinal fluid (CSF) representation, brain matter stiffness, dissipation, and nonlinearity, and differentiation of brain matter type. A new method of CSF modelling based on Reynolds lubrication theory was included to provide a more realistic brain-CSF interaction. The results indicate that solid CSF representation for this load regime misrepresents the phase lag of displacement, and that the volume of subarachnoid CSF, and inclusion of thickness variations due to gyri, are important to the resultant behavior. Stress concentrations in the deep brain are reduced by fluid redistribution and gyral contact, while inclusion of the pia mater significantly reduces cortex contact strains. These results provide direction for future modelling of SBS.

Finite element analysis of impact and shaking inflicted to a child

This study compares a vigorous shaking and an inflicted impact, defined as the terminal portion of a vigorous shaking, using a finite element model of a 6-month-old child head. Whereas the calculated values in terms of shearing stress and brain pressure remain different and corroborate the previous studies based on angular and linear velocity and acceleration, the calculated relative brain and skull motions that can be considered at the origin of a subdural haematoma show similar results for the two simulated events. Finite element methods appear as an emerging tool in the study of the biomechanics of head injuries in children.

Shaken Baby Syndrome

Unfortunately, head trauma caused by shaken baby syndrome is a common occurrence in infants and young children. The proper treatment and safety of these children can be enhanced by the nurse's ability to recognize features characteristic of this syndrome. If abuse is suspected, appropriate physicians, child-protective, and law-enforcement agencies should be notified immediately. Further research must be done to improve the understanding of the mechanisms associated with this disorder in the ultimate hope of improving the lives and outcome of infants and children.

Unexplained infant and child death: a review of sudden infant death syndrome, sudden unexplained infant death, and child maltreatment fatalities including shaken baby syndrome

PURPOSE OF REVIEW

This review will examine the most recent published literature on Sudden Infant Death, Sudden Unexplained Infant Death, infant and child death due to maltreatment, and Shaken Baby Syndrome.

RECENT FINDINGS

New recommendations from the American Academy of Pediatrics about the evaluation and prevention of possible Sudden Infant Death Syndrome cases were published this year, with a focus not only on the Back to Sleep campaign, but other factors that may contribute to the risk of Sudden Infant Death Syndrome. Additionally, the controversial issue of bed sharing is addressed, with advice given not to bed share in the first 3 months of life. The possibility of a second sudden infant death within a family is discussed. Attention is also paid to the importance of considering inflicted injury in the differential diagnosis of every unexplained infant or child death, and the recent literature on child maltreatment deaths is reviewed.

SUMMARY

The grieving family who has lost an infant should receive immediate attention and support, and a multidisciplinary investigation team should be involved as soon as possible so that a full investigation can take place. Investigation of unexplained infant or child death should always involve a thorough interview with all adults involved, as well as a proper scene investigation and post-mortem examination.

Shaken Baby Syndrome: An Odyssey

Shaken baby syndrome is evaluated in the context of its historical evolution and its veracity in referring to causal injury mechanisms. A rational assessment of the injury causation and consequent pathological states associated with the syndrome is presented. It is now evident that shaken baby syndrome evolved as a result of a faulty application of scientific reasoning and a lack of appreciation of mechanisms of injury. A brief explanation of the commonly understood usage and interface of scientific methodology and reasoning as applied to clinical medicine is given.

Perpetrator accounts in infant abusive head trauma brought about by a shaking event

OBJECTIVE

To analyze perpetrator and medical evidence collected during investigations of infant abusive head trauma (IAHT), with a view to (a) identifying cases where injuries were induced by shaking in the absence of any impact and (b) documenting the response of infant victims to a violent shaking event.

METHOD

A retrospective study was undertaken of IAHT cases investigated by the Queensland Police Service over a 10-year period. Cases of head trauma involving subdural and/or subarachnoid hematoma and retinal hemorrhages, in the absence of any evidence of impact, were defined as shaking-induced. Perpetrator statements were then examined for further evidence to support the shaking hypothesis and for descriptions of the victim's immediate response to a shaking event.

RESULTS

From a total of 52 serious IAHT cases, 13 (25%) were found to have no medical or observer evidence of impact. In 5 of those 13 cases, there was a statement by the perpetrator to the effect that the victim was subjected to a shaking event. In several cases both with and without evidence of associated impact, perpetrator accounts described an immediate neurological response on the part of the victim.

CONCLUSION

The study confirms that IAHT resulting in death or serious neurological impairment can be induced by shaking alone. In cases where the infant's medical condition was adequately described, the symptoms of head injury presented immediately.

Case Analysis of Brain-Injured Admittedly Shaken Infants

The English-language medical case literature was searched for cases of apparent or alleged child abuse between the years 1969 and 2001. Three-hundred and twenty-four cases that contained detailed individual case information were analyzed yielding 54 cases in which someone was recorded as having admitted, in some fashion, to have shaken the injured baby. Individual case findings were tabulated and analyzed with respect to shaking as being the cause for the injuries reported. For all 54 admittedly-shaken-infant cases, the provided details regarding the shaking incidents and other events are reported. Data in the case reports varied widely with respect to important details. Only 11 cases of admittedly shaken babies showed no sign of cranial impact (apparently free-shaken). This small number of cases does not permit valid statistical analysis or support for many of the commonly stated aspects of the so-called shaken baby syndrome.

Shaken baby syndrome: A biomechanics analysis of injury mechanisms

Traumatic infant shaking has been associated with the shaken baby syndrome (SBS) diagnosis without verification of the operative mechanisms of injury. Intensities for SBS have been expressed only in qualitative, unsubstantiated terms usually referring to acceleration/deceleration rotational injury and relating to falls from great heights onto hard surfaces or from severe motor vehicle crashes. We conducted an injury biomechanics analysis of the reported SBS levels of rotational velocity and acceleration of the head for their injury effects on the infant head-neck. Resulting forces were compared with experimental data on the structural failure limits of the cervical spine in several animal models as well as human neonate cadaver models. We have determined that 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 the SBS. These findings are consistent with the physical laws of injury biomechanics as well as our collective understanding of the fragile infant cervical spine from (1) clinical obstetric experience, (2) automotive medicine and crash safety experience, and (3) common parental experience. The findings are not, however, consistent with the current clinical SBS experience and are in stark contradiction with the reported rarity of cervical spine injury in children diagnosed with SBS. In light of the implications of these findings on child protection and their social and medico-legal significance, a re-evaluation of the current diagnostic criteria for the SBS and its application is suggested.

Rigid-body modelling of shaken baby syndrome

Recent reassessment of the literature on the shaken baby syndrome (SBS) has revealed a lack of scientific evidence and understanding of all aspects of the syndrome. In particular, studies have been unable to clarify the mechanisms of injury, indicating that impact, rather than shaking alone, is necessary to cause the type of brain damage observed. Rigid-body modelling (RBM) was used to investigate the effect of neck stiffness on head motion and head-torso impacts as a possible mechanism of injury. Realistic shaking data obtained from an anthropometric test dummy (ATD) was used to simulate shaking. In each study injury levels for concussion were exceeded, though impact-type characteristics were required to do so in the neck stiffness study. Levels for the type of injury associated with the syndrome were not exceeded. It is unlikely that further gross biomechanical investigation of the syndrome will be able to significantly contribute to the understanding of SBS. Current injury criteria are based on high-energy, single-impact studies. Since this is not the type of loading in SBS it is suggested that their application here is inappropriate and that future studies should focus on injury mechanisms in low-energy cyclic loading.

Paroxysmal cough injury, vascular rupture and‘shaken baby syndrome’

It is widely assumed that subdural and retinal haemorrhage in infants can only result from traumatic rupture of vulnerable blood vessels. An alternative aetiology, that of vascular rupture resulting from excessive intraluminal pressure, is presented in three disease conditions. (1) Perlman et al., studying premature neonates requiring mechanical ventilation for respiratory distress syndrome, observed "cough-like" fluctuations in oesophageal pressure greater than 18 cms H2O, whose timing matched fluctuations in anterior cerebral artery flow. When 14 out of 24 neonates were paralysed (to prevent abdominal muscle activity) intraventricular haemorrhage developed in all 10 controls but in only one of the paralysed group during paralysis. (2) New analysis of pressure data extracted from a previous study of prolonged expiratory apnoea showed alveolar collapse induced 100 mmHg intrathoracic cough pressure surges. Superior vena cava pressures up to 50 mmHg were implied, and radial artery systolic pressures over 180 mmHg recorded. (3) Bordetella pertussis bacteria attach to cilia in the airways, but do not invade the underlying tissue. The irritation causes the powerful coughing paroxysms of whooping cough. Brain haemorrhages and retinal detachment have been observed to result from the high intravascular pressures produced. The data suggest that any source of intense airway irritation not easily removed (laryngeal infection, inhalation of regurgitated feed, fluff, smoke etc.) could induce similar bleeding, a paroxysmal cough injury (PCI). Additional objective evidence of inflicted trauma is necessary to distinguish between 'shaken baby syndrome' and PCI.

Shaken baby syndrome masquerading as apparent life threatening event

A variety of diseases and disorders can present as an acute life-threatening event among which shaken baby syndrome has been recently recognized. A high index of suspicion along with an ophthalmologic evaluation and cranial imaging helps to identify this form of child abuse, which needs multidisciplinary management.

Animal models of shaken baby syndrome: revisiting the pathophysiology of this devastating injury

To better understand outcomes after early brain injuries, studies must address multiple variables including age at injury, the mechanisms and severity of injury, environmental factors (before and after injury) and developmental factors. Animal models are helpful for elucidating these different aspects. First, this paper describes a new model of shaken baby syndrome (SBS) in mice, without impact or hypoxia. Mortality was 27%; 75% of survivors had focal brain lesions consisting of haemorrhagic or cystic lesions of the white matter, corpus callosum and cerebellum. All shaken animals, with and without focal lesions, showed delayed white matter atrophy. White matter damage and atrophy were reduced by pre-treatment with an NMDA receptor antagonist, indicating that excess glutamate release contributed to the pathophysiology of the lesions. Secondly, it discusses data on neuroprotection after early brain injuries; drugs targeting the NMDA receptors cannot be used in clinical practice but indirect neuroprotection strategies including anti-NO, anti-free radicals and trophic factors hold promise for limiting the excitotoxic white matter damage induced by early injury, in particular caused by shaking, during brain development. Thirdly, it describes two experimental models in which SBS outcomes are determined when the trauma is combined with environmental influences, namely medications during the acute phase, most notably anti-epileptic drugs and rearing conditions.

Can shaking alone cause fatal brain injury? A biomechanical assessment of the Duhaime shaken baby syndrome model

A biomechanical model of a one-month old baby was designed and tested by Duhaime and co-workers in 1987 in an attempt to assess the biomechanics of the shaken baby syndrome (SBS). The study implied that pure shaking alone cannot cause fatal head injuries, a factor which has been applied in criminal courts. In an attempt to test the validity of the model a preliminary study was undertaken in which a replica was constructed and tested. The broad description of the design and construction of the Duhaime model allowed for variations and therefore uncertainties in its reproduction. It was postulated therefore that differences in certain parameters may increase angular head accelerations. To further investigate this observation, an adjustable replica model was developed and tested. The results indicated that certain parameter changes in the model did in fact lead to an increase in angular head acceleration. When these parameter changes were combined and an injurious shake pattern was employed, using maximum physical effort, the angular head acceleration results exceeded the original Duhaime et al. (1987) results and spanned two scaled tolerance limits for concussion. Additionally, literature suggests that the tolerance limits used to assess the shaking simulation results in the original study may not be reliable. Results from our study were closer to the internal head injury, subdural haematoma, tolerance limits. A series of end point impacts were identified in the shake cycles, therefore, an impact-based head injury measure (Head Injury Criterion - HIC) was utilized to assess their severity. Seven out of ten tests conducted resulted in HIC values exceeding the tolerance limits (critical load value, Stürtz, 1980) suggested for children. At this present stage the authors conclude that it cannot be categorically stated, from a biomechanical perspective, that pure shaking cannot cause fatal head injuries in an infant. Parameters identified in this study require further investigation to assess the accuracy of simulation and increase the biofidelity of the models before further conclusions can be drawn. There must now be sufficient doubt in the reliability of the Duhaime et al. (1987) biomechanical study to warrant the exclusion of such testimony in cases of suspected shaken baby syndrome.

Shaken baby syndrome

Shaken baby syndrome is a significant cause of infant morbidity and mortality and is widely recognized in the medical literature. Classic signs include retinal hemorrhage, subdural or subarachnoid hemorrhage, and associated fractures. Most victims are younger than 6 months old and have been affected by violent shaking with rapid angular deceleration and possible terminal impact. This article summarizes issues related to clinical presentation, diagnosis, risk factors, and interventions for healthcare professionals.

[Lumbar puncture and early neuroimaging in complex febrile seizures. Report of a case of shaken infant syndrome]

INTRODUCTION

Febrile convulsions are one of the most frequent pathologies seen in paediatric emergencies. The diagnosis of febrile seizures is clinico evolutionary and is easily established once the acute process is overcome and a normal state is restored in the child. The differential diagnosis is established with the processes that associate fever and convulsions in children between the ages of 1 month and 6 years, many of which require specific treatment. Certain complementary examinations, essentially a blood test, lumbar puncture and neuroimaging, are needed to identify them. Shaken infant syndrome is a form of physical abuse which includes the presence of intracranial traumatic injury, retinal haemorrhage and, in general, the absence of other physical signs of traumatic injury in the child.

CASE REPORT

An 8 month old infant who presented a convulsive seizure on the left side of the body which coincided with an axillary temperature of 38 C that remitted with intravenous diazepam 40 minutes after onset. An early cranial computerised tomography (CT) scan led to a diagnosis of shaken infant syndrome.

DISCUSSION

This case constitutes an argument in favour of performing an early cranial CT scan in complex febrile convulsions and in prolonged or partial non provoked seizures. We highlight the risks involved in performing a lumbar puncture in the absence of suspected non complicated acute bacterial meningitis. The diagnostic usefulness of an early CT scan in diagnosing such an important problem as shaken infant syndrome must also be noted, due to the risk of repetition and its high morbidity and mortality rates.

Ophthalmology of shaken baby syndrome

Retinal hemorrhages are an important indicator of Shaken Baby syndrome. However, a thorough description which includes the number, type, and distribution pattern of hemorrhages can be useful in determining their specificity. In particular, numerous pre-retinal, intraretinal, and subretinal hemorrhages extending out to the edges of the retina and/or splitting of the retina (traumatic retinoschisis) seem to be particularly indicative of shaking with a very narrow differential diagnosis. Shaking appears to be a key element in creating hemorrhagic retinopathy.