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Forensic Neuropathology

Overview

Head injuries are very common injuries and the cause of more than one half of all traumatic deaths. A great variety of injuries may affect the scalp, skull, and brain. Head injuries can be classified into 2 major categories of brain damage, primary and secondary damages. The primary damages are those that occur at the moment of the injury and include scalp lacerations, skull fractures, contusions and lacerations of the brain, diffuse axonal injury, and the intracranial hemorrhages. The secondary damages are those produced by complications arising from the primary damages and include the lesions produced by increased intracranial pressure, ischemia, brain swelling, and infection.

An alternative method of classifying the pathology of head injury is into focal and diffuse injuries. Focal injuries are those which can be seen by the naked eye or by imaging studies; these injuries result from direct impact to the head (eg, scalp laceration and contusion, skull fracture, epidural hemorrhage, subdural hemorrhage, brain contusion). Diffuse injuries are those which cannot be fully appreciated by the naked eye, although some imaging techniques may provide evidence of these injuries; these injuries result from inertial loading of the head and include interhemispheric subdural hemorrhage and diffuse axonal injury.

History

Head injury or traumatic brain injury traumatic brain injury (TBI) has been a large contributor to mortality and morbidity throughout the ages, but a number of developments of modern living have served to increase the number of cases of TBI in the present day. One of these developments is the proliferation of motor vehicles, which are common causes of TBI. Another commonality in the modern world is the continuing violence from gunshot wounds (GSWs). Even the increased longevity of the population has contributed to TBI from falls in the elderly and infirm.

Epidemiology

Head injuries cause up to one half of all traumatic deaths and comprise a significant portion of the cases examined by medical examiners. These injuries occur in a variety of circumstances, including vehicular accidents, gunshot wounds, falls, assaults, and child abuse. Head injury rates are greatest in urban areas, with as many as 32 per 100,000 population, of which 50% are from vehicular accidents, 20-40% from gunshot wounds, 10% from falls, and 5-10% from assaults.

Overview of the Entity

Traumatic brain injury (TBI) can be classified into static and dynamic injuries, depending on the rate with which force is loaded to the head. Static injuries occur over longer time periods—usually greater than 200 milliseconds (msec)—and cause crushing head injury. Crushing head injuries are relatively rare and are caused when a massive weight crushes the stationary head and results in comminuted fractures of the calvarium, facial skeleton, and skull base, with fracture contusions and fracture lacerations of the brain.

Dynamic head injuries account for the great majority of head injuries at all ages. These injuries occur when force is rapidly loaded to the head in less than 200 msec. Dynamic head injury can be caused by impulsive loading that causes the head to move, either by direct impact to the head, which is free to move, or by an action to the body that causes the head to move. Impulsive loading will impart inertial movement of the brain within the cranial cavity. The unsupported head will rotate at some point where it joins the cervical spine, and the rotational movement of the head will create differential movement of the brain and skull because of the different rigidities of the 2 structures.

Because the dura is attached to the skull, differential movement between the skull and the brain may strain and tear bridging veins to the point of failure and cause bleeding into the subdural space. The inertial movement of the brain is maximal in the cortex but extends into the brain with greater forces. It is this inertial movement of the brain that results in traumatic diffuse axonal injury.

Impact loading produces several effects to the head; it causes contact injuries that include scalp laceration and skull fracture; creates pressure wave propagation into the cranial cavity and brain; and causes brain contusions. Impact loading also causes inertial brain movement that may be either translational or rotational.

Indications for the Procedure

Examination of the head is carried out in most autopsies, although a few autopsies omit the head when interest is focused on only a heart, lung, or abdominal issue. Sometimes families ask that the head be spared when an autopsy is being carried out. In most autopsies, however, the examination of the head is of vital importance.

Hospital autopsies are significantly different in their approach and interests than autopsies done by medical examiners and forensic pathologists. Hospital autopsies are primarily focused on determining why the patient has died, evaluating the effects of therapeutic efforts, and determining the accuracy of diagnostic procedures.

Forensic autopsies are carried out to determine the cause of death and the manner of death (natural, accident, suicide, homicide, undetermined), as well as to carry out other functions relating to identification of the body, obtaining evidence and toxicology specimens from the body, evaluation of injury patterns, documentation of disease states, evaluating mechanisms of injury, retrieval and protection of personal property, and consideration of forensic issues, such as time of death.

In determining the manner of death, the pathologist needs to have additional information regarding the circumstances surrounding the death and may also need other information, such as past medical history. The autopsy findings are then considered along with all the additional information before decisions are made about manner of death.

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