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CME/CE: Neurology
Table 1
Definition of Mild Traumatic Brain Injury 7
A patient with mild traumatic brain injury has experienced a traumatically induced physiologic disruption of brain function, as
manifested by at least one of the following:
1. Any loss of consciousness
2. Any loss of memory about events immediately before or after the accident
3. Any alteration in mental state at the time of the accident (feeling dazed, confused, seeing stars)
4. Focal neurologic deficits that may or may not be transient but in which the severity of the injury does not exceed the following:
loss of consciousness for 30 minutes or less; after 30 minutes, an initial Glasgow Coma Scale score of 13 to 15; posttraumatic
amnesia lasting not more than 24 hours
This definition includes:
1. The head being struck
2. The head striking an object
3. The brain undergoing an acceleration/deceleration movement (i.e., whiplash) without direct external trauma to the head
Developed by the American Congress of Rehabilitation Medicine, http://www.acrm.org/pdf/TBIDef_English_Oct2010.pdf
Blast-related events are the leading
cause of head injury in the military,
followed in order by the other events
mentioned above. 4 As a result of several
factors, the number of concussions
reported is lower than the number of
actual occurrences.
Many patients who experience concussion
and receive medical care do not
have a TBI diagnosis recorded, especially
when multiple injuries are present. 5 In
addition, up to 25% of patients with a
concussion do not seek medical care. 6
Reasons include lack of outward physical
injury, symptom resolution before
they can seek medical care, and lack of
awareness that they should seek care.
In 2007, the Department of Defense
(DoD) started TBI screening programs
for service members who returned from
war zones, in order to identify soldiers
who may have sustained a concussive
event while deployed. Today, screening
is performed on all service members at
the end of deployment or when evacuated
from theater due to injury. Because
so many service members and former
service members are seen outside the
military healthcare system, providers
in civilian settings should be aware of
the incidence and causes of concussion
in this population.
Mechanisms of Injury
The mechanisms of injury in an mTBI
encompass one or more of the following:
• Direct contact, such as something
hitting the head while the head is at rest,
causing focal damage.
• Acceleration in combination with
deceleration, also known as coup–contrecoup,
in which the brain moves within
the skull. This can cause damage to multiple
areas, depending on how the brain
slides. This can occur in a car accident
that produces a forward and backward
motion of the head, causing the brain
to slide. The frontal and occipital lobes
absorb this impact.
• Rotational forces that cause shearing
of the cerebral white matter axons.
• A blast overpressure wave, followed
by possible further concussive forces, such
as being hit by debris, being thrown or
inhaling fumes.
Diagnostic Criteria
The American Congress of Rehabilitation
Medicine established criteria for mTBI 7
(Table 1) in 1993, defining it as a traumatically
induced physiologic disruption of
brain function. The diagnosis of mTBI
does not mean the symptoms are mild;
at times these symptoms can be disabling.
In 1997, the American Academy of
Neurology published a sports concussion
grading system (Table 2). 8
An essential common element in the
two sets of criteria is a traumatic blow or
jolt to the head that causes an inability
for the brain to function normally, even
if it is for seconds.
In our current state of heightened
awareness of TBI, especially among
military personnel, it is not uncommon
for providers and patients to diagnose a
concussion based on symptoms alone.
But if alteration of consciousness (AOC)
or greater has not occurred, a concussion
diagnosis is not appropriate. In addition
to being inaccurate, a symptom-based
diagnosis may delay treatment of the
real diagnosis.
The natural history of a concussion
involves resolution within minutes to
several months. 9-11 In patients older than
40 and in patients with preexisting conditions,
recovery may take longer. 10 When
symptoms last more than 3 months, the
diagnosis of post-concussion syndrome
may apply.
The percentage of patients who have
unrelenting symptoms ranges from 5%
to 15%. 12,13 Influencing factors include
pre-existing conditions, psychiatric conditions,
chronic pain, substance abuse,
secondary gain, unemployment and lack
of support systems. 14
Repetitive Injury
Education about the prevention of repeat
brain injury is vital yet often overlooked.
A patient with a concussion may not be
thinking clearly and may put himself or
herself at risk for additional head injuries.
In addition, the patient’s reaction time
may be slowed.
Several studies have documented the
consequences of repeat concussions.
Repetitive brain injury can lead to longer
lasting symptoms, chronic headaches,
slower response time and decreased academic
scores. 15
Recent studies of football players who
sustained multiple concussions identified
changes to brain pathology, known
as chronic traumatic encephalopathy, 16
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