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:
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.
