Pediatr Radiol (2014) 44 (Suppl 4):S632–S640 DOI 10.1007/s00247-014-3061-6 SPECIAL ISSUE: ABUSIVE HEAD TRAUMA Distinguishing accidental from inflicted head trauma at autopsy Mary E. Case Received: 8 January 2014 /Accepted: 15 May 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract This article will discuss accidental and Introduction inflicted head injuries in infants and young children and how forensic pathologists distinguish between This article will discuss how forensic pathologists distinguish these types of injuries. The article begins with a con- accidental from inflicted head trauma at autopsy. It is imperative sideration of the special and unique features of the that the autopsy findings are considered in conjunction with the anatomy and development of the child’s head and neck medical history, beginning with the birth of the child and coming and then relates these features to the mechanisms of forward to the time of the injury, the family’s medical and social traumatic brain injury and how these unique features services history, the circumstances of the injury event, and all of influence the mechanisms of injury. The article very the investigative information derived from reports from law specifically notes that accidental head injuries in young enforcement and other agencies as well as information from children that occur in and around the home are focal genetic screening and toxicology evaluations. This article will head injuries in distinction to inflicted head injuries, consider the mechanisms of traumatic head injury and how these which are diffuse brain injuries. The article discusses mechanisms create various types of pathological findings seen the mechanisms by which traumatic brain injury causes in either accidental or inflicted head injury. This article will loss of consciousness and relates those mechanisms to further discuss the mechanisms by which consciousness is the differences in the clinical features that occur in affected by neurotrauma and what the differences are between both accidental and inflicted head injury. The article the manner by which focal and diffuse head injuries cause a loss discusses and illustrates the pathological findings in of consciousness. It is important that the process for arriving at accidental head injuries consisting of the crushing head the decision of whether an injury is the result of an accident or is injuries and the head injuries sustained in short falls a homicide is thoughtful, deliberate and well delineated. This including epidural hemorrhage and focal subdural hem- article aims to provide an understanding of the deliberative orrhage. The article discusses and illustrates the patho- process utilized by the forensic pathologist in distinguishing logical findings that occur in inflicted head trauma, accidental from inflicted head trauma. including subdural and subarachnoid hemorrhages and retinal and optic nerve sheath hemorrhages. Anatomical and developmental characteristics Keywords Non-accidental injury . Head injury . of the child’sheadandneck Postmortem . Mechanism of injury . Child Understanding head injuries that occur from either accidental or inflicted trauma in children requires an appreciation of the very unique features of the brain, skull and neck. These structures are in the process of maturing in young children * M. E. Case ( ) and injuries during this period will differ from those injuries St. Louis University Health Sciences Center, 1402 S. Grand Blvd., St. Louis, MO 63104, USA that occur later in life. The differences in these structures e-mail: [email protected] remain until mid-childhood but are most marked in the very Pediatr Radiol (2014) 44 (Suppl 4):S632–S640 S633 young. In early life, the skull is very thin and pliable so that the skull. When acceleration-deceleration of the head causes dif- infant head can pass through the birth canal. Such a skull ferential motion between the brain and the skull, the dura provides little protection against impact and force can pass moves with the skull causing the bridging veins that arise readily through the unossified bones. The human brain is a from the surface of the cerebrum and ascend into the dura to large organ at birth and grows very rapidly in infancy and be stretched and torn resulting in bleeding into the subdural early childhood, yet it is not mature for many years. The space. Rotational inertial motion of the brain results in damage young child’s head is very heavy, 15% to 20% of the body’s to axonal processes, traumatic axonal injury. weight, compared to the adult whose head is 2% to 3% of the A further classification of head injury is into focal and body’s weight. The consistency of the young human brain is diffuse brain injury categories. Impact to the head causes focal very soft due to a high water content, the immaturity of the contact injuries, which include scalp contusion and laceration, glial cells, the lack and immaturity of the myelination of the skull fracture, brain contusions, epidural hemorrhage and axons, and the small size of the axons. These latter features focal subdural hemorrhage. Focal injuries can be seen by the make the brain in the young child more easily damaged by naked eye of the pathologist on gross examination of the brain strains and shearing forces [1]. The subarachnoid space in a and by the radiologist on imaging with CT or MR. Impact, if young child is thinner than later in life [2]. The thickness of the forceful enough, can also create inertial brain movement. subarachnoid space determines how much buttressing effect the Diffuse brain injury is the result of inertial brain motion and subarachnoid space will have, which is obviously much less in includes interhemispheric subdural hemorrhage and traumatic the young brain. Lastly, the strength of the neck muscles of the diffuse axonal injury. Traumatic diffuse brain injury is not young child is much less than that at older ages. Acceleration- visible to either the pathologist on gross inspection at autopsy deceleration of the head is the most common mechanism by or to the radiologist on CT or MR [4–8]. which head injuries occur and these injuries are facilitated by weak neck muscles in support of the heavy head. Neck muscle strength and the ability to prevent head motion on impact or Mechanisms of loss of consciousness in traumatic brain impulse are critical factors in preventing head injury [3]. injury The separation of traumatic brain injury into focal and diffuse Mechanisms of traumatic brain injury brain injuries is helpful in considering how these types of injury result in clinical features, particularly in regards to Fully appreciating distinctions between accidental and levels of consciousness. Focal brain injury results in symp- inflicted head injury in young children requires a consider- toms due to either destruction of brain tissue, which can ation of the mechanisms by which head injury occurs in all happen in a brain contusion, or by creating increased intracra- age groups as well as a consideration of the special anatomical nial pressure through an enlarging hematoma or brain swell- and developmental characteristics of the young human head ing. In an injury in which increasing intracranial pressure and neck. Traumatic head injury can be divided into static and leads to loss of consciousness, there is a progression over time dynamic injuries based upon the rate at which force is loaded of descending levels of consciousness. This is primarily the onto the head. Static injuries occur over longer time periods, progression due to tentorial herniation and takes place in hours greater than 200 ms and eventuate in crushing head injury. or in some cases less time but never abruptly or instantaneous- Such injuries occur when the stationary head is compressed by ly. In cases of diffuse brain injury, the mechanism of loss of a heavy weight and the calvarium, basilar skull and facial consciousness is traumatic axonal injury. In these cases, the skeleton sustain comminuted fractures resulting in the brain change in level of consciousness is abrupt and immediate at sustaining fracture lacerations and fracture contusions. Static the time of the injury. This type of unconsciousness is desig- head injuries are not very common but occur occasionally in nated as “traumatic unconsciousness” [7]. children in certain circumstances that will be further discussed in the following sections. Dynamic head injuries are the most common type of injury at all ages and occur when force is Pathology of accidental head trauma rapidly loaded to the head in less than 200 ms. Dynamic injuries result when the head is caused to move (impulsive To illustrate the numbers of cases of accidental vs. inflicted loading) either by direct impact to the head, which is free to injury occurring in and around the home in children examined move, or by an action to the body that causes the head to move in a large medical examiner’s office, the author gathered data such as a collision with the body or by shaking the body. from the St. Louis metropolitan area with a population of 2 Forceful dynamic loading can create inertial movement of the million during the time periods 1975 to 1985 and 1986 to brain within the cranial cavity. Inertial brain motion occurs 1999. This study excluded children who died from gunshot due to the difference in rigidities between the brain and the wounds, drowning out of the home, house fires and vehicular S634 Pediatr Radiol (2014) 44 (Suppl 4):S632–S640 accidents. From 1975 to 1985, there were 160 deaths studied loss of consciousness or amnesia for the event. In these of which 63 (39%) were accidents, 70 (43%) were homicides injuries, there is no rotational inertial brain motion and con- and 27 (17%) were undetermined. Of the 63 accidental deaths, sciousness is maintained until the brain is markedly distorted 39% were under 1 year old, 28% were between 1 and 2 years and the deep central gray structures are damaged [7, 11].