Mild Traumatic Brain Injury
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Definition
The Mild Traumatic Brain Injury Committee of the Head Injury
Interdisciplinary Special Interest Group of the American Congress of
Rehabilitation Medicine (1993) defines mild traumatic brain injury (Mild TBI) as
a traumatically induced physiological disruption of brain function as manifested
by as least one of the following:
- Any period of loss consciousness.
- Any loss of memory for events immediately before or after the accident.
- Any alteration in mental state at the time of accident.
- Focal neurological deficit that may or may not be transient but does not
exceed:
- loss of consciousness of approximately 30 minutes or less,
- an initial Glascow Coma Scale score of 13-15 after 30 minutes
- post traumatic amnesia (PTA) of no more than 24 hours
In the sports medicine literature it is more common to see the term
"concussion" to describe an injury to the head that produces a brief alteration
in consciousness and post traumatic amnesia. In this section the term concussion
will be used interchangeably with "Mild TBI".
It is important to understand that the head does not need to be struck in
order for a person to have sustained a mild traumatic brain injury. For example,
a motor vehicle accident that results in significant "whiplash" injury may
produce a Mild TBI. Similarly a baby may be shaken without having its head
struck and still sustain a brain injury. Also, the term "mild" discribes the
initial insult relative to degree of neurological severity. There may be no
correlation with the degree of short term (see "early symptoms" below and
functional disability). A "mild" TBI may not be necessarily trivial or
insignificant. Some Mild TBI's can result in significant disability (e.g. the
high school quarterback who sustains a mild TBI cannot remember play options to
call and is confused by new information presented in the classroom). Mild TBI
may also be unappreciated or undiagnosed if the patient presents with other,
more significant general medical or othopedic problems. Oftentimes the cognitive
symptoms associated with Mild TBI (see below) are not readily evidenced in the
emergency room, physicians office or hospital because of the lower "demands" on
cognitive functioning in these settings. Instead, the cognitive symptoms may
first be experienced when the person returns to work, school and/or home which
all place a higher "demand" on cognitive functioning.
There are numerous ways a child can sustain a Mild TBI. Reporting on a series
of 937 children, Hahn and Mclone (1993) indicated that the most common cause of
Mild TBI was a fall (N=3), followed by bicycle/pedestrian motor vehicle accident
(N=158), assault (N=17), abuse (N=17) and bicycle (N=8). This data is generally
consistent with national estimates. The incidence of Mild TBI in sports is being
increasing recognized. For example, Powell and Barber-Foss (1999) reported that
of the 23,566 injuries sustained in ten high schools sports (e.g. football,
soccer, hockey, etc)during a three year period, 1219 (5.5%) involved a Mild TBI.
It has been estimated that Mild TBI affects 158 out of 100,000 children per year
with the ratio of boys to girls injured being estimated to be 2:1 (Segalowitz & Brown,
1991).