include an assessment of cognitive and emotional
functioning, as well as effort or motivation. Because
these patients are commonly seen in forensic evalua-
tions, where malingering is more likely, specific cog-
nitive tests of effort should be administered. Symptom
exaggeration or suboptimal performance can also be
assessed on measures of emotional functioning.Nature, Symptoms, and
Outcomes From mTBI
Mild traumatic brain injury is a trauma to the brain
that results in a brief loss of consciousness; a loss of
memory for events immediately before or after the
event, but not greater than 24 hours; or an alteration in
mental status (e.g., feeling dazed, disoriented, or
confused). When evaluated immediately postinjury,
mTBIs are characterized by a high Glasgow Coma
Scale score (between 13 and 15), which is a measure
of the ability to follow eye-opening, motor-response,
and verbal-response commands. When these injury
characteristics are present, and there is no evidence of
neurological damage, such as hemorrhage or contu-
sion on neuroimaging (e.g., CT or MRI scan) of the
brain, the mTBI is considered to be uncomplicated. A
mild complicated TBI has not only a similarly short
loss of consciousness and posttraumatic amnesia but
also evidence of brain damage on neuroimaging (e.g.,
skull fracture), thus making it a more severe injury.
Uncomplicated mTBIs can be contrasted with moder-
ate or severe TBIs in which loss of consciousness and
posttraumatic amnesia are significantly longer, typi-
cally measured in days or weeks, and are often accom-
panied by neuroimaging evidence of brain damage.
Common causes of mTBIs include the head being
struck by an object, the head striking an object, or the
brain undergoing an acceleration/deceleration move-
ment, or whiplash, without direct external trauma to the
head. The latter injury is common in motor vehicle
accidents. The term mTBIis synonymous with concus-
sion,with the latter term often used to describe the
injury in athletics. These can be graded on their level of
severity and are most common in contact sports such as
football and hockey. Of the different levels of brain
injury severity, mTBIs are by far the most common,
accounting for more than 75% of all TBIs.
Common symptoms in the initial days and weeks
post-mTBI can include a range of physical, cognitive,
and psychological changes. Common physical symp-
toms include headache, nausea, vomiting, dizziness,blurred vision, and sleep disturbance; common cogni-
tive deficits include attention and memory deficits.
Psychologically, symptoms such as anxiety, irritabil-
ity, or depression may be present. Depending on
severity, these symptoms can interfere with an indi-
vidual’s ability to function effectively. These acute
symptoms are due to temporary dysfunction of the
brain, such as metabolic changes, diminished cerebral
blood flow, and impaired neurotransmission sec-
ondary to the injury. Although most neurons recover,
a small number of neurons may degenerate and die.
Nevertheless, the brain tends to recover quite quickly
and naturally in an uncomplicated mTBI and there is
typically significant improvement in symptoms within
the first few days postinjury. Moreover, research has
demonstrated that the vast majority of individuals are
essentially symptom free and return to baseline levels
of functioning within a few days to weeks, and some-
times a few months, after their injury. Recovery in
athletes tends to be even more rapid, as these individ-
uals are often highly motivated to recover and return
to play. Nevertheless, a small number of individuals,
fewer than approximately 5%, have prolonged and, at
times, disabling symptoms postinjury that present a
more complex clinical picture. Historically, various
terms have been used to describe these patients, but
today they are typically diagnosed with postconcus-
sion syndrome. Not surprisingly, these individuals
tend to seek continued psychological and medical
treatment and may seek legal redress for their injury.
There is controversy about individuals with poor
outcomes after uncomplicated mTBI and the cause of
their persisting symptoms. While some have argued
that these symptoms may be due to undetected and
persisting brain abnormalities, most clinicians and
researchers argue that other factors besides mTBI must
be considered. For instance, many of these patients are
in litigation and thus have external incentives to com-
plain of persisting symptoms, even years after injury.
Research has also demonstrated that those individuals
who have had previous psychological or neurological
problems or other life stressors tend to recover more
poorly. Older age does not appear to be a risk factor for
poor outcome after a single mTBI, although this is
controversial, and the impact of repeated mTBIs and
age (i.e., NFL players or boxers) may increase the
chances of developing dementia in later life. Clearly,
ongoing psychological or substance abuse postinjury,
medical or pain complications from other injuries sus-
tained in the accident (e.g., orthopedic), or additional500 ———Mild Traumatic Brain Injury, Assessment ofM-Cutler (Encyc)-45463.qxd 11/18/2007 12:43 PM Page 500