It should be mentioned again that subarachnoid blood of some degree is very common after all degrees of head injury. A problem that sometimes arises in cases that display both contusions and subarachnoid blood is the possibility that a ruptured aneurysm was the initial event and that a resultant fall caused the contusions. In cases where the subarachnoid blood is concentrated around one of the major vessels of the circle of Willis, an angiogram is justified to exclude the latter possibility. Also in elderly patients, it has been difficult to determine whether a fall had been the cause or the result of a subarachnoid or an intracerebral hemorrhage. These subjects are addressed further in Chap. 33.
This condition is seen in the first hours after injury and may prove rapidly fatal. The CT scan shows enlargement of both hemispheres and compression of the basal cisterns and ventricles. There is usually no papilledema in the early stages, during which the child hyperventilates, vomits, and shows extensor posturing. The assumption has been that this represents a loss of regulation of cerebral blood flow and a massive increase in the blood volume of the brain. The administration of excessive water in intravenous fluids may contribute to the problem and should be avoided. Inappropriate secretion of antidiuretic hormone also exaggerates the swelling in some children. We have not observed this complication in adults. Fear of massive brain swelling from a second impact after a concussion has been raised as a rationale for keeping youngsters from returning to athletic activity, but there is only limited evidence for the existence of this entity in adults as noted by McCrory and Berkovic.
This form of craniocerebral trauma in infants is known in large emergency practices and is now missed less frequently than in the past as practitioners have been sensitized to consider it as a form of child abuse when an infant or child is injured. As the name implies, the inciting trauma is typically violent shaking of the body or head of an infant, resulting in rapid acceleration and deceleration of the cranium. The presence of this type of injury is inferred from the distribution and types of lesions on imaging studies or autopsy examination, but precision in examination is paramount because of its forensic and legal implications. The diagnosis is suspected from the combination of subdural hematomas and retinal hemorrhages, as summarized by Bonnier and colleagues. Sometimes there are occult skull fractures, but more often, there is little or no direct cranial trauma. Additional lesions may be evident on diffusion-weighted MRI, particularly in the white matter of the corpus callosum and the temporo-occipito-parietal region. This syndrome confers a high risk for slowing of cognitive development; in extreme cases there may be acquired microcephaly reflecting brain atrophy consequent to both contusions and infarctions. A low initial Glasgow Coma Scale score, retinal hemorrhages, and skull fractures are associated with poor outcomes. Old and recent fractures in other parts of the body should arouse suspicion of this syndrome.
The descriptions in the preceding pages apply to blunt, nonpenetrating injuries of the skull and their effects on the brain. In the past, the care of penetrating craniocerebral injuries was mainly the interest of the military surgeon, but—with the persistence of violent crime in society—such cases have also become commonplace on the emergency wards of general hospitals.
In civilian life, missile injuries are essentially caused by bullets fired from rifles or handguns at high velocities. Air is compressed in front of the bullet so that it has an explosive effect on entering tissue and causes damage for a considerable distance around the missile track. Missile fragments, or shrapnel, from exploding shells, mines, grenades, or bombs are the usual causes of penetrating cranial injuries in wartime. The cranial wounds that result from missiles and shrapnel have been classified by Purvis as tangential, with scalp lacerations, depressed skull fractures, and meningeal and cerebral lacerations; penetrating, with in-driven metal particles, hair, skin, and bone fragments; and through-and-through wounds.