Neuropathology and Ophthalmological Pathology of Fatal Central Nervous System Injuries in Young Children: Forensic Neuropathology of Deaths of Children Under Age 2, 2008-2016, in Central Missouri

Nonaccidental head injuries are significant causes of morbidity and mortality among young children. Despite broad agreement among medical experts, controversies remain over diagnostic criteria, including from autopsies, because of opinions expressed by a small group of expert witnesses who testify for defendants in suspected child homicide cases. We reviewed 249 autopsies in children 2 years old and younger from the files of our Medical Examiner office in the University of Missouri School of Medicine done between January 1, 2008 and December, 31, 2016. Because of gradually instituted mandatory examination of spinal cords and retinas, we had 127 autopsies with brain examinations by a neuropathologist plus retinal examinations of which 67 also had spinal cord examinations. Results were correlated with clinical records, police and EMS reports, and imaging. We found that subdural hematomas, cerebral edema, and retinal hemorrhages were mostly limited to autopsy findings in children who suffered from fatal head trauma, whether accidental (3 cases) or inflicted (14); they were not encountered in cases of homicide by other mechanisms or from natural diseases including infections, brain tumors, SIDS/SUID, or SUDC. Two cases with no other evidence of head trauma had focal retinal hemorrhages. We advocate for examination of retinas and spinal cords in all autopsies of children in this age group.

Characteristics associated with spine injury on magnetic resonance imaging in children evaluated for abusive head trauma

BACKGROUND

Spine injuries are increasingly common in the evaluation for abusive head trauma (AHT), but additional information is needed to explore the utility of spine MRI in AHT evaluations and to ensure an accurate understanding of injury mechanism.

OBJECTIVE

To assess the incidence of spine injury on MRI in children evaluated for AHT, and to correlate spine MRI findings with clinical characteristics.

MATERIALS AND METHODS

We identified children younger than 5 years who were evaluated for AHT with spine MRI. Abuse likelihood was determined a priori by expert consensus. We blindly reviewed spine MRIs and compared spinal injury, abuse likelihood, patient demographics, severity of brain injury, presence of retinal hemorrhages, and pattern of head injury between children with and without spine injury.

RESULTS

Forty-five of 76 (59.2%) children had spine injury. Spine injury was associated with more severe injury (longer intensive care stays [P<0.001], lower initial mental status [P=0.01] and longer ventilation times [P=0.001]). Overall abuse likelihood and spine injury were not associated. Spinal subdural hemorrhage was the only finding associated with a combination of retinal hemorrhages (P=0.01), noncontact head injuries (P=0.008) and a diagnosis of AHT (P<0.05). Spinal subdural hemorrhage was associated with other spine injury (P=0.004) but not with intracranial hemorrhage (P=0.28).

CONCLUSION

Spinal injury is seen in most children evaluated for AHT and might be clinically and forensically valuable. Spinal subdural hemorrhage might support a mechanism of severe acceleration/deceleration head injury and a diagnosis of AHT.

Development of a Model of Hemispheric Hypodensity ("Big Black Brain")

Subdural hematoma (SDH) is the most common finding after abusive head trauma (AHT). Hemispheric hypodensity (HH) is a radiological indicator of severe brain damage that encompasses multiple vascular territories, and may develop in the hemisphere(s) underlying the SDH. In some instances where the SDH is predominantly unilateral, the widespread damage is unilateral underlying the SDH. To date, no animal model has successfully replicated this pattern of injury. We combined escalating severities of the injuries and insults commonly associated with HH including SDH, impact, mass effect, seizures, apnea, and hypoventilation to create an experimental model of HH in piglets aged 1 week (comparable to human infants) to 1 month (comparable to human toddlers). Unilateral HH evolved over 24 h when kainic acid was applied ipsilateral to the SDH to induce seizures. Pathological examination revealed a hypoxic-ischemic injury-type pattern with vasogenic edema through much of the cortical ribbon with relative sparing of deep gray matter. The percentage of the hemisphere that was damaged was greater on the ipsilateral versus contralateral side and was positively correlated with SDH area and estimated seizure duration. Further studies are needed to parse out the pathophysiology of this injury and to determine if multiple injuries and insults act synergistically to induce a metabolic mismatch or if the mechanism of trauma induces severe seizures that drive this distinctive pattern of injury.

En Bloc Examination of the Neck in Pediatric Homicide Cases: A Proper Way for Complete Assessment of Neck Trauma

The necks of infants and young children are not only anatomically different from adults, but are also supported by much weaker musculoskeletal systems and are therefore prone to trauma as a result of extension/flexion (shaking) or contact trauma to the head. Shaking cervical spine injuries can occur at much lower levels of head velocity and acceleration than those reported for shaken baby syndrome. The proper method for a comprehensive and detailed examination of the neck in pediatric homicide and suspected homicide cases is the en bloc examination of the neck, because the standard examination of the spinal cord not only distorts the anatomical relationship of the cord and osteocartilagenous structures, but also excludes the cervical nerves, ganglia, and the vertebral arteries from being evaluated. Interpretation of gross and microscopic findings using this method requires experience and knowledge of the anatomical relationship and common artifacts, such as epidural, focal intradural, or even isolated nerve hemorrhage to avoid misinterpretation. It is our opinion that this method should be applied to all pediatric homicide or suspected homicide cases, but is not suited for routine or nonsuspicious cases as it will add to the time and cost of medical examiner's operations.

A Conceptual Overview of Axonopathy in Infants and Children with Allegedly Inflicted Head Trauma

Fatal, allegedly inflicted pediatric head trauma remains a controversial topic in forensic pathology. Recommendations for systematic neuropathologic evaluation of the brains of supposedly injured infants and children usually include the assessment of long white matter tracts in search of axonopathy - specifically, diffuse axonal injury. The ability to recognize, document, and interpret injuries to axons has significant academic and medicolegal implications. For example, more than two decades of inconsistent nosology have resulted in confusion about the definition of diffuse axonal injury between various medical disciplines including radiology, neurosurgery, pediatrics, neuropathology, and forensic pathology. Furthermore, in the pediatric setting, acceptance that "pure" shaking can cause axonal shearing in infants and young children is not widespread. Additionally, controversy abounds whether or not axonal trauma can be identified within regions of white matter ischemia - a debate with very significant implications. Immunohistochemistry is often used not only to document axonal injury, but also to estimate the time since injury. As a result, the estimated post-injury interval may then be used by law enforcement officers and prosecutors to narrow "exclusive opportunity" and thus, identify potential suspects. Fundamental to these highly complicated and controversial topics is a philosophical understanding of the diffuse axonal injury spectrum disorders.

Demystifying the Medical Literature

The published literature is not just the ongoing record of current medical and scientific knowledge; it is a record of the past and can give an eye toward future knowledge. Reading the published literature can give a view of the evolution of knowledge on a particular question, the growth of a discipline, the identification of new diseases, and the refinement of diagnostic tests. The reality is that most busy physicians read only the abstract of an article. The purpose of this article is to place published medical literature into a context and to provide some considerations for critically evaluating articles. This paper will provide historic background of evidence-based medicine and medical publications. Specific strategies for critical literature appraisal are highlights and pitfalls to avoid are outlined.

The Value of Anthropology in Medicolegal Death Investigation of Pediatric Nonaccidental Injury

Forensic anthropologists have made remarkable contributions to the medicolegal investigation of nonaccidental injury in pediatric cases. They have created standard nomenclature for fracture descriptions. Anthropologists have developed novel techniques that increase the sensitivity of the pediatric autopsy. They have performed biomechanical research that enables reconstruction of events surrounding death. Also, anthropology practitioners have developed several reference guides on the subject of nonaccidental injury that are of value to forensic pathologists. These advancements assist forensic pathologists in the accurate classification of cause and manner of death in pediatric cases.

The Evolution of the Autopsy

Contrary to claims that the autopsy has not significantly changed over the past 150 years, this article will demonstrate the remarkable evolution of the autopsy at the hands of its practitioners since the 15th century and into the 21st. A solid understanding of the ongoing evolution of autopsy technique helps provide a firm argument for the continued utilization of the autopsy in daily practice and for the advancement of medicine.

Cervical Ganglia and Nerve Root Injury: Evidence for Respiratory Arrest as Initiating Injury in Pediatric Head Trauma

Cervical ganglia and nerve root injury with resultant paralysis of the phrenic nerve is proposed as a mechanism of injury in “shaken baby syndrome” or nonaccidental head injury of children. We report autopsy findings of a 22-month-old girl in which cervical ganglia and nerve hemorrhage was present along with the triad of encephalopathy, bilateral retinal hemorrhage, and bilateral subdural, intradural, and subarachnoid hemorrhages. Clear evidence of near immediate respiratory arrest was documented from first responder medical reports, juvenile witness statements, and perpetrator confession. The narrowing of time of injury from the anatomic findings at autopsy allowed investigative efforts to focus on a single individual and cleared several other adults with access to the child. Additional technical notes based on our experience are provided for users of cervical neck dissection. Hemorrhage in the tissues surrounding the vertebral artery raises a potential additional injury site in cases of neck injury.

Assessment and Diagnosis of Trauma in the High Cervical Spine Using Dissection, Radiography, Computed Tomography and Magnetic Resonance Imaging

Cervical spine trauma, particularly that occurring at the craniocervical junction (CCJ), is the cause of a significant number of deaths each year. Although some forms of injury within the high cervical spine will be obvious during routine external and internal examination procedures, others cannot be diagnosed without advanced methods. The anatomy of the CCJ is complex and notoriously difficult to evaluate at autopsy. While specialized autopsy techniques allow thorough evaluation of this region, they are inconsistently understood and performed. Furthermore, although radiography has long been a mainstay of forensic pathology practice, it is not routinely utilized to assess for cervical spine trauma. As advanced radiology techniques become more regularly available in a postmortem setting (computed tomography [CT] and magnetic resonance [MR] imaging), forensic pathologists are offered additional tools that facilitate accurate diagnoses in the high cervical spine. Fundamental to the appropriate use and interpretation of autopsy and radiologic techniques is an understanding of the involved anatomy. The structures within the CCJ, advanced dissection methods, and fundamentals of cervical spine radiology are reviewed in this manuscript. Where available, autopsy evaluation of the CCJ will be complemented by radiography, CT, and MR imaging. In some circumstances, dissection and/or autopsy could be supplanted by the use of postmortem CT and MR scanning.

Investigation of Sudden Unexpected Infant Deaths

The investigation of infant death is complex and requires synergy between multiple agencies including law enforcement, Child Protective Services, medicolegal death investigators, and forensic pathologists. Prior to the forensic pediatric autopsy, the death investigator must identify the types of death scenes involved (e.g., hospital, residence, daycare) and document the details of the scene. Interviews must be conducted with the caregivers and other family members (including doll reenactments), law enforcement, pediatricians, and emergency medical personnel. The forensic pathologist must be able to conduct a comprehensive pediatric forensic autopsy and be aware of the specific challenges related to cases of sudden unexpected infant deaths. This article provides an overview of infant death investigation, discussing the roles and responsibilities of the medicolegal death investigator and the forensic pathologist.

Imaging of spinal injury in abusive head trauma: a retrospective study

BACKGROUND

Spinal imaging has been a neglected part of abusive head trauma (AHT) imaging. As most of the radiographs and CT spine are negative in AHT in infants, the cervical spine is assumed to be normal. There is increasing evidence in the role of injury to brainstem and cervical cord in the pathogenesis of AHT. In addition, in courts of law, there is fierce debate about AHT, its mimics and other disparate nontraumatic diagnoses explaining the neuroradiological and skeletal findings. However, this discussion ignores the evidence and significance of spinal injury. We sought to study the cervical spine in an AHT cohort to understand the true prevalence of spinal injuries in AHT and contrast it with cohorts of accidental and nontraumatic groups to give the clinicians a robust diagnostic tool in evaluating AHT.

OBJECTIVE

The purpose of this study is to compare the relative incidence of spinal ligamentous and soft-tissue abnormalities on spinal MRI among three groups of children ages <48 months: 1) those with AHT, 2) those with accidental trauma, and 3) those with nontraumatic conditions.

MATERIALS AND METHODS

This comparative study included 183 children who underwent spine MRI: 67 with AHT, 46 with accidental trauma and a clinical suspicion of spinal injury, and 70 with nontraumatic conditions. Clinical and radiographic findings were collected in all cases and were analyzed retrospectively to identify MRI evidence of traumatic spinal injuries. The incidence of spinal injuries among the three groups was compared. The incidence of spinal ligamentous injuries was calculated for those with and without radiographic evidence of hypoxic-ischemic encephalopathy. All comparisons were performed using Fisher exact test with P < 0.05 considered statistically significant.

RESULTS

Cervical spine ligamentous injuries (predominantly the nuchal, atlanto-occipital and atlanto-axial ligaments) were present in 78% of the AHT group, 46% of the accidental trauma group and 1% of the nontraumatic group; all of these differences were statistically significant. Among the AHT group, ligamentous injuries were statistically correlated with evidence of brain ischemia.

CONCLUSION

Injury to the cervical spinal posterior ligamentous complex is common in AHT and even more prevalent than in clinically symptomatic traumatic cases. The high correlation between the radiographic findings of occipitocervical ligamentous injuries and hypoxic-ischemic brain injury is consistent with an interpretation that transient upper occipitocervical spinal cord injury in AHT leads to disordered breathing and results in hypoxic-ischemic encephalopathy. We recommend imaging the entire spine in AHT to properly identify and classify these injuries.

National Association of Medical Examiners Position Paper: Recommendations for the Postmortem Assessment of Suspected Head Trauma in Infants and Young Children

The National Association of Medical Examiners convened a panel to create a position paper for recommendations for the investigation of infant deaths due to inflicted head trauma. The correct certification of both the cause and manner of death is dependent upon an evaluation of all available data including information derived from the investigation, scene, postmortem examination, and ancillary studies. This paper provides recommendations for the forensic pathologist on what constitutes the dataset to be produced during the postmortem examination of infants who have died of, or have apparently died of, inflicted head trauma. Specifically, this paper describes 1) procedures, 2) ancillary laboratory tests, and 3) forms of documentation that are important in the investigation of these deaths. The evaluation and documentation of such infant deaths involves the production of a detail oriented and thoroughly documented examination that is independently reviewable to support the multitude of inquiries that may follow from the public and the criminal justice system.

Subdural Hemorrhage and Hypoxia in Children Less than Two Years Old

The majority of subdural hemorrhages (SDH) are due to acceleration-deceleration forces associated with blunt head injury. So-called spontaneous subdural hemorrhages are described with coagulopathies, hemodialysis, hemophilia, and as extensions of hemorrhages due to other causes such as ruptured cerebral artery aneurysms. Recently, some have proposed that hypoxia causes subdural hemorrhage in infants and children.

Materials and Methods

Of 1,190 deaths of children younger than two years of age, we analyzed 366 that were due to asphyxial mechanisms, respiratory disease, prematurity, seizures, and perinatal hypoxic-ischemic encephalopathy. All underwent autopsy and 97% included a consultant neuropathology examination.

Results

Of the 366 decedents, hypoxic-ischemic encephalopathy (HIE) was diagnosed in 73 (20%) and evidence of subdural hemorrhage in 34 (9%). Of the 73 HIE deaths, 14 (19%) had SDH. Among these 14, 12 involved prematurity and/or perinatal HIE. Among the 20 fatalities with SDHs but without HIE, all were premature infants and/or had a SDH that pathologically pre-dated the putative hypoxic-ischemic event. Of the 34 SDHs, 24 were organized neomembranes and ten were organizing hemorrhages.

Discussion

SDHs that are not caused by acceleration-deceleration forces are routinely recognized in infants and children. Usually, they are clinically silent and may be associated with prematurity and perinatal birth events. At autopsy, subdural neomembranes frequently are incidental findings in infants and children who die from a variety of causes. This study does not support the theory that hypoxic-ischemic injury in infants and children causes subdural hemorrhage.

The "Shaken Baby" syndrome: pathology and mechanisms

The "Shaken Baby" syndrome (SBS) is the subject of intense controversy; the diagnosis has in the past depended on the triad of subdural haemorrhage (SDH), retinal haemorrhage and encephalopathy. While there is no doubt that infants do suffer abusive injury at the hands of their carers and that impact can cause catastrophic intracranial damage, research has repeatedly undermined the hypothesis that shaking per se can cause this triad. The term non-accidental head injury has therefore been widely adopted. This review will focus on the pathology and mechanisms of the three physiologically associated findings which constitute the "triad" and are seen in infants suffering from a wide range of non-traumatic as well as traumatic conditions. "Sub" dural bleeding in fact originates within the deep layers of the dura. The potential sources of SDH include: the bridging veins, small vessels within the dura itself, a granulating haemorrhagic membrane and ruptured intracranial aneurysm. Most neuropathologists do not routinely examine eyes, but the significance of this second arm of the triad in the diagnosis of Shaken Baby syndrome is such that it merits consideration in the context of this review. While retinal haemorrhage can be seen clinically, dural and subarachnoid optic nerve sheath haemorrhage is usually seen exclusively by the pathologist and only rarely described by the neuroradiologist. The term encephalopathy is used loosely in the context of SBS. It may encompass anything from vomiting, irritability, feeding difficulties or floppiness to seizures, apnoea and fulminant brain swelling. The spectrum of brain pathology associated with retinal and subdural bleeding from a variety of causes is described. The most important cerebral pathology is swelling and hypoxic-ischaemic injury. Mechanical shearing injury is rare and contusions, the hallmark of adult traumatic brain damage, are vanishingly rare in infants under 1 year of age. Clefts and haemorrhages in the immediate subcortical white matter have been assumed to be due to trauma but factors specific to this age group offer other explanations. Finally, examples of the most common causes of the triad encountered in clinical diagnostic and forensic practice are briefly annotated.

Inference in Forensic Pathology

Forensic pathologists make inferences about cause and manner of death. Those inferences have come under increasing scrutiny by the courts, by social critics of our findings, and by society at large. Much of this criticism is due to our inability to explain our inferential process. Forensic pathologists should be able to cogently explain the reasoning behind their findings, and express it in terms useful to stakeholders. This requires that we have a basic understanding of different kinds of inference and the scientific method, how they are used and their limitations. Medical diagnosis is not a simple matter of application of cookbook-style inferential laws, but involves a combination of deduction, induction, abduction, dialectic, and informal inference. There are significant differences between the way physicians make inferences compared to how they justify them. A discussion of different kinds of inference, inferential fallacies, evaluation of evidence, causation, and the scientific method is provided, with illustrations from the practice of forensic pathology.