NEW YORK (Reuters Health) –– A mild blow to the head may
cause more brain damage than previously thought. California
researchers have found that head injuries that cause concussion can
lead to changes that resemble brain damage in the comatose, and
these changes can last for weeks.
The finding is important for athletes, especially those in contact
sports such as football and ice hockey, who may be at risk for
repeated concussions in short frames of time if they continue to
“We were very surprised,” said Dr. Marvin Bergsneider from the
University of California, Los Angeles, lead author of the study
published in the Journal of Neurotrauma. “It really defies standard
The researchers took positron emission tomography (PET) scans
that show glucose uptake indicating brain activity of 42 people
who had suffered mild head injuries such as concussion within the
previous month. Most of the head injuries were due to motor
vehicle accidents or falls. The results of the study showed that 84% of
the patients (36) had a reduction in the metabolic rate of glucose uptake
in the brain.
The investigators performed Glasgow Coma Scale (GCS) tests on
these study participants. The GCS assesses a person's ability to
answer simple questions, such as who and where they are,
Bergsneider explained. A level of 3 is deeply comatose, while 15 is
the best score.
The team found that 22 of the 36 patients had comatose–level GCS
scores (3 to 8). Of the 14 that had higher scores, six had initial
scores that were likely lower than 8 but had improved by the time
of the PET scan, Bergsneider said.
These patients may have appeared to have mild concussions but
truly had more severe injury since small blood clots could be
detected on the scan, Bergsneider noted.
It was remarkable that these people functioned as well as they did
with such low GCS scores, he said. “They were awake” and able
to answer simple questions, but had really intense testing been
done, “we would probably find deficits,” Bergsneider said.
It seems that the brain shuts off some functions in order to heal, he
suggested, although more research needs to be conducted to confirm that
this is what is happening. The changes in glucose use by the brain seen on
the PET resolved itself in all patients by the end of the month, he noted.
The significance of this finding lies in the fact that many people,
particularly athletes, suffer repeated concussions and may be
severely damaging their brain, Bergsneider told Reuters Health.
Furthermore, they often put themselves at risk by continuing to
play after a period of unconsciousness.
Once the brain has been injured, it “just can't respond to another
injury or insult.... There's not a lot of knowledge about this
vulnerability to a second concussion,” he said. “We're raising a
little alarm. This needs to be studied better.”
Dissociation of Cerebral Glucose Metabolism and Level of Consciousness
During the Period of Metabolic Depression Following Human Traumatic Brain Injury
J Neurotrauma 2000; 17 (5) May: 389–401