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When Brain Injury Occurs

by Dennis P. Swiercinsky, Ph.D., ABPN

Traumatic brain injury occurs when a physical force to the head causes the brain to suddenly and violently slam against the interior bony structure of the skull. Trauma to the head can cause nerve cells in the brain to stretch, tear, and pull apart, making them unable to relay messages from one part of the brain to another. The head striking an object (a windshield or the ground) at a fast rate of speed or something striking the head (a flying or falling object) can cause brain injury. 

Brain injury does not have to involve direct trauma to the head. Whiplash injury or violent shaking of the head can also cause brain injury. Injury to brain cells interferes with all sorts of information processing—thinking, remembering, seeing, controlling and coordinating bodily movements, and controlling emotions. Traumatic brain injury can range from relatively mild to catastrophically severe depending on multiple factors including degree of force, multiple trauma, neurological complications, and timeliness of emergency medical treatment.

Mild Traumatic Brain Injury

Clinicians classify head (or, more correctly, brain injury) based on quality or length of change in consciousness and length of amnesia (memory loss). Both loss of consciousness (or even a semi-conscious state) and amnesia are directly caused by the sudden trauma and tearing of nerve cells. When this trauma occurs, the brain simply cannot maintain its normal functioning and shuts down (causing unconsciousness) or partially shuts down (causing a feeling of being dazed), until cellular functioning can recover. "Mild brain injury" refers to the extent of loss of consciousness (30 minutes or less) and length of amnesia (24 hours or less), not to the functional effects. The diagnosis can be made if even one of the following conditions is observed: (1) loss of consciousness of any length, (2) amnesia of any length, (3) altered consciousness (e.g., being "dazed"), or (4) focal neurological deficits (e.g., temporary vision loss, or a seizure). Even a "mild" traumatic brain injury can result in permanent, life-altering consequences.

Effects of Traumatic Brain Injury

Some of the functional consequences of mild traumatic brain injury include slowed thinking, memory and concentration problems, poor judgment, emotional disorder, and difficulty making decisions. These problems are a result of "diffuse axonal injury," or damaged nerve cells. This type of injury impacts the processing of electro-chemical messages within the brain, leading to the destruction of previously existing complex interrelated brain connections. As a result, complex or unfamiliar tasks become frustrating, irritability prevails, and the person attempts to cope with a brain that just seems always to function in a mental fog. A wide variety of complicating cognitive and emotional reactions can evolve—some of which may be permanent.

Effects of traumatic brain injury vary from one person to another. Both the physical nature of the injury and the personal characteristics and resources of the individual contribute to the functional difficulties. Some individuals may recover relatively well while other may experience major life-altering effects.

Diagnosis of Traumatic Brain Injury

X-ray, MRI (magnetic resonance imaging), and CT (computerized tomography) can sometimes diagnose head and brain injuries by showing areas of fracture, hemorrhage, or other kinds of tissue injury. These techniques are usually employed initially in the case of any head trauma to check for life threatening bleeding or swelling in brain tissue. However, traumatic brain injury (especially if mild) often involves scattered disconnection among neurons and supportive tissue, stretched and damaged axon membranes (known as diffuse axonal injury), chemical injury due to neurotransmitter toxicity, and cellular dysfunction due to changes in brain chemistry. These kinds of changes to brain cells often do not result in sufficient change in the tissue density to be detected by conventional imaging techniques. Even if diffuse axonal injury does cause some subtle change in tissue density, the injury is so scattered throughout the brain that there is insufficient focal concentration of injury to yield detection by these procedures. Often, more elaborate imaging techniques such as SPECT (single-photon emission computed tomography) or PET (positron emission tomography) can detect changes due to brain injury because these techniques measure brain cell metabolism, not tissue density. In addition to these imaging techniques, a variety of neurological and behavioral tests are used to diagnose brain injury.

Neuropsychological Assessment

Due to the typically diffuse nature of many cases of brain injury, structural changes may not be easily detected by conventional imaging procedures. However, traumatic brain injury also causes behavioral or functional changes. Assessing functional change is a major procedure for diagnosing brain injury. Objective and scientifically created neuropsychological tests are sensitive to these trauma-induced functional changes and sometimes provide the best—and only—technique for revealing brain dysfunction. By combining data from a thorough interview and results of neuropsychological and sometimes personality tests, the neuropsychologist creates a functional profile that can be compared to the kinds of profiles usually produced by persons with various kinds of brain injury. Neuropsychological examination also differentiates emotional and personality changes (such as depression or posttraumatic stress disorder) from trauma-induced changes.

The Role of the Neuropsychologist

Only specifically trained psychologists who specialize in neuropsychology (the study of brain and behavior relationships) are qualified to administer and interpret neuropsychological tests. Neurologists and neurosurgeons often administer a variety of mental status procedures but these are neither standardized nor sensitive enough to detect subtle dysfunction that can be revealed by objective neuropsychological tests. Neurologists, neurosurgeons, and neuropsychiatrists are medical doctors who rely on physical procedures and trained observations for diagnosis, and medical/surgical techniques for treatment. Neuropsychologists are clinical psychologists who, through the use of standardized behavioral assessments, seek to understand the complex interactions of psychological and biological components that produce dysfunctional behavior.

Neuropsychological Diagnosis

Brain injury is diagnosed by comparing the results of neuropsychological tests that are sensitive to changes caused by brain injury with neuropsychological tests that are not sensitive to changes caused by brain injury. Similarly, some procedures differentiate pre-existing emotional and personality characteristics that existed before injury. "Differential Diagnosis" is the hallmark of a comprehensive neuropsychological examination. The neuropsychologist sorts out the pre-existing emotional and psychological factors from the acquired changes due directly to brain injury.


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