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.].

Thresholds for the assessment of inflicted head injury by shaking trauma in infants: a systematic review.

In order to investigate potential causal relations between the shaking of infants and injuries, biomechanical studies compare brain and skull dynamic behavior during shaking to injury thresholds. However, performing shaking tolerance research on infants, either in vivo or ex vivo, is extremely difficult, if not impossible. Therefore, infant injury thresholds are usually estimated by scaling or extrapolating adult or animal data obtained from crash tests or whiplash experiments. However, it is doubtful whether such data accurately matches the biomechanics of shaking in an infant. Hence some thresholds may be inappropriate to be used for the assessment of inflicted head injury by shaking trauma in infants. A systematic literature review was conducted to 1) provide an overview of existing thresholds for head- and neck injuries related to violent shaking, and 2) to identify and discuss which thresholds have been used or could be used for the assessment of inflicted head injury by shaking trauma in infants. Key findings: The majority of studies establishing or proposing injury thresholds were found to be based on loading cycle durations and loading cycle repetitions that did not resemble those occurring during shaking, or had experimental conditions that were insufficiently documented in order to evaluate the applicability of such thresholds. Injury thresholds that were applied in studies aimed at assessing whether an injury could occur under certain shaking conditions were all based on experiments that did not properly replicate the loading characteristics of shaking. Somewhat validated threshold scaling methods only exist for scaling concussive injury thresholds from adult primate to adult human. Scaling methods that have been used for scaling other injuries, or for scaling adult injury thresholds to infants were not validated. There is a clear and urgent need for new injury thresholds established by accurately replicating the loading characteristics of shaking.

Modeling of inflicted head injury by shaking trauma in children: what can we learn? : Part II: A systematic review of mathematical and physical models.

Various types of complex biomechanical models have been published in the literature to better understand processes related to inflicted head injury by shaking trauma (IHI-ST) in infants. In this systematic review, a comprehensive overview of these models is provided. A systematic review was performed in MEDLINE and Scopus for articles using physical (e.g. dolls) and mathematical (e.g. computer simulations) biomechanical models for IHI-ST. After deduplication, the studies were independently screened by two researchers using PRISMA methodology and data extracted from the papers is represented in a "7-steps description", addressing the different processes occurring during IHI-ST. Eleven papers on physical models and 23 papers on mathematical models were included after the selection process. In both categories, some models focus on describing gross head kinematics during IHI-ST events, while others address the behavior of internal head- and eye structures in various levels of detail. In virtually all physical and mathematical models analyzed, injury thresholds are derived from scaled non-infant data. Studies focusing on head kinematics often use injury thresholds derived from impact studies. It remains unclear to what extent these thresholds reflect the failure thresholds of infant biological material. Future research should therefore focus on investigating failure thresholds of infant biological material as well as on possible alternative injury mechanism and alternative injury criteria for IHI-ST.

[Trauma craneal no accidental en niños: costo económico directo de la atención médica en un hospital de tercer nivel].

INTRODUCTION: Abusive head trauma (AHT) is an extreme form of physical abuse that is produced by abruptly shaking an infant or toddler. OBJECTIVE: To describe the direct economic cost of care during hospitalization of 14 children with confirmed diagnosis of AHT in a pediatric hospital. METHOD: Analysis of the cost of disease in patients with AHT attended to between 2001 and 2010. Partial direct economic cost of medical care (days of hospital stay, laboratory tests and imaging studies, surgical procedures and subspecialist consultations) was calculated adjusting for inflation, with year 2001 taken as base year. Patients were classified in three groups (moderate, severe and fatal AHT). Descriptive and sensitivity analysis was carried out. RESULTS: Patients with severe AHT generated higher medical care costs ($105,794.88 ± 33,201.91) in comparison with the group of moderate ($37,012.95, ± 7,154.87) and fatal AHT ($18,595.04 ± 6424.47) (p <0.05). Total cost was $665,467.98 Mexican pesos ($71,249.25 international dollars). CONCLUSIONS: Total cost for the 14 patients was an elevated figure, as in other parts of the world. The direct economic cost is closely related to the severity of the clinical presentation.

INTRODUCCIÓN: El trauma craneal no accidental (TCNA) es una forma extrema de abuso físico que se produce por la sacudida brusca de un lactante o preescolar. OBJETIVO: Describir el costo económico directo de la atención durante la hospitalización de 14 niños con diagnóstico confirmado de TCNA en un hospital pediátrico. MÉTODO: Análisis del costo de la enfermedad en pacientes con TCNA, atendidos entre 2001 y 2010. Se realizó análisis descriptivo y de sensibilidad. Se calculó costo económico directo parcial de la atención médica (días de estancia hospitalaria, exámenes de laboratorio y gabinete, procedimientos quirúrgicos y consultas por subespecialista), ajustado por la inflación, se tomó como año base 2001. Los pacientes se clasificaron en tres grupos: TCNA moderado, severo y fatal. RESULTADOS: Los pacientes con TCNA severo generaron mayor costo en la atención médica ($105 794.88 ± 33 201.91), en comparación con el grupo con TCNA moderado ($37 012.95 ± 7154.87) y fatal ($18 595.04 ± 6424.47) (p < 0.05). El costo total fue de 665 467.98 pesos mexicanos (71 249.25 dólares internacionales). CONCLUSIONES: El costo total de los 14 pacientes fue una cifra elevada como en otras partes del mundo. El costo económico directo se relaciona estrechamente con la gravedad del cuadro clínico.

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.

Cyclic Head Rotations Produce Modest Brain Injury in Infant Piglets.

Repetitive back-and-forth head rotation from vigorous shaking is purported to be a central mechanism responsible for diffuse white matter injury, subdural hemorrhage, and retinal hemorrhage in some cases of abusive head trauma (AHT) in young children. Although animal studies have identified mechanisms of traumatic brain injury (TBI) associated with single rapid head acceleration-decelerations at levels experienced in a motor vehicle crash, few experimental studies have investigated TBI from repetitive head rotations. The objective of this study was to systematically investigate the post-injury pathological time-course after cyclic, low-velocity head rotations in the piglet and compare them with single head rotations. Injury metrics were the occurrence and extent of axonal injury (AI), extra-axial hemorrhage (EAH), red cell neuronal/axonal change (RCNAC), and ocular injury (OI). Hyperflexion/extension of the neck were purposefully avoided in the study, resulting in unscaled angular accelerations at the lower end of reported infant surrogate shaking kinematics. All findings were at the mild end of the injury spectrum, with no significant findings at 6 h post-injury. Cyclic head rotations, however, produced modest AI that significantly increased with time post-injury (p < 0.035) and had significantly greater amounts of RCNAC and EAH than noncyclic head rotations after 24 h post-injury (p < 0.05). No OI was observed. Future studies should investigate the contributions of additional physiological and mechanical features associated with AHT (e.g., hyperflexion/extension, increased intracranial pressure from crying or thoracic compression, and more than two cyclic episodes) to enhance our understanding of the causality between proposed mechanistic factors and AHT in infants.

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.

Update on injury mechanisms in abusive head trauma--shaken baby syndrome.

Violently shaking a baby leads to clinical presentations ranging from seizures to cardiopulmonary arrest. The main injuries sustained are retinal hemorrhages, subdural hemorrhages, and sometimes fractures and spine injury. It is important to have a global view of the injuries sustained by the infant to correctly discuss the biomechanical aspects of abusive head trauma. Recent works based on finite element models have shown that whiplash-shaking alone is enough to generate vitreo-retinal traction leading to retinal hemorrhage and to cause the rupture of bridging veins leading to subdural hemorrhage. We will review the main papers dealing with the mechanisms of shaken baby syndrome and present the most relevant hypothesis concerning the biomechanical aspects of injuries related to shaken baby syndrome.

Biomechanical studies in an ovine model of non-accidental head injury.

This paper presents the head kinematics of a novel ovine model of non-accidental head injury (NAHI) that consists only of a naturalistic oscillating insult. Nine, 7-to-10-day-old anesthetized and ventilated lambs were subjected to manual shaking. Two six-axis motion sensors tracked the position of the head and torso, and a triaxial accelerometer measured head acceleration. Animals experienced 10 episodes of shaking over 30 min, and then remained under anesthesia for 6h until killed by perfusion fixation of the brain. Each shaking episode lasted for 20s resulting in about 40 cycles per episode. Each cycle typically consisted of three impulsive events that corresponded to specific phases of the head's motion; the most substantial of these were interactions typically with the lamb's own torso, and these generated accelerations of 30-70 g. Impulsive loading was not considered severe. Other kinematic parameters recorded included estimates of head power transfer, head-torso flexion, and rate of flexion. Several styles of shaking were also identified across episodes and subjects. Axonal injury, neuronal reaction and albumin extravasation were widely distributed in the hemispheric white matter, brainstem and at the craniocervical junction and to a much greater magnitude in lower body weight lambs that died. This is the first biomechanical description of a large animal model of NAHI in which repetitive naturalistic insults were applied, and that reproduced a spectrum of injury associated with NAHI.

Experimental analyses of the retinal and subretinal haemorrhages accompanied by shaken baby syndrome/abusive head trauma using a dummy doll.

INTRODUCTION: We explored several modes of violent shaking using a dummy doll with an eyeball model to reproduce abusive events that lead to retinal haemorrhages (RH) seen in shaken baby syndrome or abusive head trauma (SBS/AHT). MATERIALS AND METHODS: A dummy doll equipped with an eyeball model was prepared. The eyeball model was filled with a model of vitreous body, i.e. agar gel or water, and was with a pressure sensor to measure normal stress. RESULTS: The modes of shaking were classified into three patterns, i.e. fast shaking with the fore arms, fast shaking with the whole arms and synchronized shaking with the whole arms. The frequency of the cyclic acceleration-deceleration history experienced by the head of the dummy doll was 5.0, 4.0 and 2.2 Hz, respectively, with the maximum acceleration of 20, 20 and 60 m/s(2), respectively. We considered the last of these three modes of shaking as possibly corresponding to the worst case of violent shaking. This mode of shaking could be instructed to volunteers who acted as imitate perpetrators, and resulted in both increased peak intensities of the acceleration experienced by the head of the dummy doll and increased stresses on the retina at the posterior pole of the eyeball model. DISCUSSION: The time integral of the stress through a single cycle of shaking was 107 Pa·s, much larger than that of a single event of fall, which resulted in 60-73 Pa·s. Taking into account that abusive shaking is likely to include multiple cycles, the time integral of the stress due to abusive shaking can be even larger. This clear difference may explain why RH in SBS/AHT is frequent, while RH in accidental falls is rare.

Development of a finite element/multi-body model of a newborn infant for restraint analysis and design.

A finite element/multi-body model of a newborn infant has been developed by researchers at the University of Windsor. The geometry of this model is derived from a Nita newborn hospital training mannequin. It consists of 17 parts: eight upper and lower limb segments, the torso, head, and a seven-segment neck with seven translational and eight rotational joints. Anthropometry is consistent with hospital growth charts, measurements requested from health professionals and data from the open literature. The biomechanical properties of the model (i.e. joint stiffnesses) are implementations of data identified in the open literature. The model has been validated with respect to studies of the biomechanics of shaken baby syndrome, infant falls and the Q0 anthropomorphic testing device. A significant conclusion of this study is that the kinetics of the Q0 neck is not biofidelic. This model is currently used in an analysis of airway patency for infants in modern automotive child restraints.

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.

Study of an infant brain subjected to periodic motion via a custom experimental apparatus design and finite element modelling.

This paper presents a rig that was specifically designed to simulate the shaking of mechanical models of biological systems, especially those related to shaken baby syndrome (SBS). The scope of this paper includes the testing of an anthropomorphic model that simulates an infant head and provides validation data for complex finite element (FE) modelling using three numerical methods (Lagrangian, Arbitrary-Lagrangian-Eulerian (ALE) and Eulerian method) for fluid structure coupling. The experiments for this study aim to provide an understanding of the influence of two factors on intracranial brain movement of the infant head during violent shaking: (1) the specific paediatric head structure: the anterior fontanelle and (2) the brain-skull interface. The results show that the Eulerian analysis method has significant advantages for the FSI modelling of brain-CSF-skull interactions over the more commonly used methods, e.g. the Lagrangian method. To the knowledge of the authors, this methodology has not been discussed in previous publication. The results indicate that the biomechanical investigation of SBS can provide more accurate results only if the skull with paediatric features and the brain-skull interface are correctly represented, which were overlooked in previous SBS studies.

Retinal haemorrhage in abusive head trauma.

Paediatric abusive head injury may have grave consequences, especially when characterized by repetitive acceleration-deceleration forces (shaken baby syndrome). Death occurs in approximately 30% and permanent neurologic damage in up to 80% of the victims. Retinal haemorrhages are a cardinal sign seen in approximately 85% of cases. In most cases haemorrhages are preretinal, intraretinal and subretinal, too numerous to count, and involving the entire retinal surface extending to the ora serrata. Traumatic macular retinoschisis is a lesion with important diagnostic significance. Vitreoretinal traction appears to be the mechanism of haemorrhage and schisis formation along with a possible role of orbital tissue trauma from repetitive acceleration-deceleration forces. Ophthalmologists must carefully document ocular findings. Appropriate autopsy examination should include ocular and orbital tissue removal. Although there is a wide differential diagnosis for retinal haemorrhages, clinical appearance, when considered in the context of systemic and laboratory findings, usually leads to the correct diagnosis.