Adult Brain Injuries

Traumatic Brain Injury
Traumatic brain injury (TBI), also called acquired brain injury or simply head injury, occurs when a sudden trauma causes damage to the brain. TBI can result when the head suddenly and violently hits an object, or when an object pierces the skull and enters brain tissue. Symptoms of a TBI can be mild, moderate, or severe, depending on the extent of the damage to the brain. A person with a mild TBI may remain conscious or may experience a loss of consciousness for a few seconds or minutes. Other symptoms of mild TBI include headache, confusion, lightheadedness, dizziness, blurred vision or tired eyes, ringing in the ears, bad taste in the mouth, fatigue or lethargy, a change in sleep patterns, behavioral or mood changes, and trouble with memory, concentration, attention, or thinking. A person with a moderate or severe TBI may show these same symptoms, but may also have a headache that gets worse or does not go away, repeated vomiting or nausea, convulsions or seizures, an inability to awaken from sleep, dilation of one or both pupils of the eyes, slurred speech, weakness or numbness in the extremities, loss of coordination, and increased confusion, restlessness, or agitation.

Introduction & Defintion
Oxygen is required for normal brain functioning. Hypoxic-anoxic injuries result when there is a substantial (partial, or hypoxic) or a complete (total, or anoxic) lack of oxygen supplied to the brain. This diminished oxygen supply to the brain may produce profound cognitive (thinking), physical (movement), and affective (emotional) impairments which may be slow to recover. As a result, hypoxic-anoxic injury (HAI) can have a catastrophic impact, both in terms of functional (what a person can do) deficits as well as the costs involved in treatment and the disruption it can cause among associated families. One of the problems that has plagued affected individuals and their families is the relative lack of easy-to-read, accessible information to answer their questions. This fact sheet will help answer some of these questions.

If oxygen is not available, a cascade-effect of problems occurs. Oxygen and glucose are responsible, either directly or indirectly, for a variety of chemical reactions which are involved in the production of important chemical-like brain neurotransmitters (e.g., dopamine, norepinephrine, and serotonin). Such neurotransmitters act to regulate the brain's many complex functions. One particular neurotransmitter, acetylcholine (Ach), seems to play a direct role in memory.

HAI can be caused by a variety of disease processes and injuries. Although there are several possible reasons for anoxic injury, hypoxic-ischemic injury (HII) is the most common.

Stagnant (ischemic) anoxia (also called hypoxic-ischemic injury, or HII)--not enough cerebral blood flow to carry blood to the brain. Injury can be localized (such as ischemic strokes) or generalized (circulatory collapse secondary to cardiac arrhythmias or cardiac arrest). This type of injury causes general, diffuse damage to the cerebral cortex and cerebellum. Areas of the brain that are very sensitive to lack of oxygen include the hippocampus (a region critical for memory), borderzone areas of the cerebral cortex (the parieto-occipital and frontoparietal regions), cerebellum, basal ganglia, and spinal cord (thoracic region).

Below is a summary of the more frequent causes of cardiac arrest, perhaps the most common cause of ischemic anoxia: