Know how to recognize head injuries

Donya Betancourt, Pediatrician, drdonya@hotmail.com

Head injuries can range from relatively minor damage to the scalp and face, such as lacerations, abrasions and bruising, to more serious consequences, involving damage to the brain.

The brain, rather soft tissue with a consistency somewhere between egg white and jello, is covered by three membranous layers. The outermost, the dura mater, is connected to the inside of the skull at various suture points that serve to suspend the brain within the skull.

The brain sits atop the brain stem, an extension of the spinal cord which passes out through the base of the skull via a hole known as the foramen magnum.

Brain injuries arise from three characteristics of this brain- skull anatomy: * The rigidity and internal contours of the skull (the age and shape of the skull) * The incompressibility of brain tissue (the inelasticity of the brain) * The susceptibility of the brain to shearing forces.

The first two give rise to contusions or hematomas (i.e. bleeding) on the surface of the brain, one of the most common injuries. The third, susceptibility to shearing forces, plays a role primarily in injuries that involve rapid and forceful movements of the head, such as in motor vehicle accidents.

In these situations rotational forces, such as in whiplash- type injuries, are particularly important. These forces, associated with the rapid acceleration and deceleration of the head, are smallest at the point of rotation of the brain near the lower end of the brain stem and successively increase at increasing distances from this point. The resulting shearing forces cause different levels in the brain to move relative to one another. This movement produces stretching and tearing of axons (nerve) and the insulating myelin sheath (nerve sheath), injuries that are the major cause of loss of consciousness in a head trauma.

Small blood vessels are also damaged, causing bleeding (petechial hemorrhages) deep within the brain. Collectively, these injuries can result in swelling of the brain. If the pressure within the skull is not relieved through surgery, cooling or medication, the brain will gradually be pushed down through the foramen magnum. Nuclei in the brain stem controlling breathing and cardiac (heart) function will eventually be compressed, resulting in death.

Returning now to the symptoms of head injury, a great deal of work has been directed toward using these symptoms to classify the severity of head injury.

While traumatic brain injury occurs much less frequently, it is important to know how it is identified and what to do for the person. Loss of consciousness, even for a very brief period, is one of the clearest indications that the brain may have been affected by a blow to the head. A confusional state, involving uncertainty about time, date and location, and/or a period of memory loss of the events surrounding the head injury, are also indicators of trauma to the brain.

The Glasgow Coma Scale is very useful for predicting early outcome from a head injury. The effects of head injury most often observed in these assessments can be classified generally into three categories: physical, cognitive and behavioral. The physical effects of head injuries include symptoms such as seizures, loss of motor speed and coordination and the presence of abnormal movement such as tremors and spasticity.

Cognitive changes involve disorders of attention, concentration and memory, problems with understanding or producing speech, difficulties with initiating and planning daily activities and poor reasoning and judgement. The behavioral effects include agitation and irritability, verbal and physical aggressiveness, impulsivity, depression and suicidal thoughts, and an egocentric or self-centered orientation in interpersonal relationships.

Identification of these effects of head injury is a very important first step in helping the person and his family. Too often, though, this assessment and early treatment stage is where the process stops.