Nutrition in Combat Sports

100 P. McCrory et al.
Neuropsychological tests were also completed at baseline and again at 6-month
follow-up, and again no evidence of brain damage was apparent at either timepoint,
or when compared to age-matched controls. Other prospective studies have
also not demonstrated any MR abnormalities related to boxing. [72, 73]
One of the earliest studies using MRI in boxers was by Cabanis et al., who noted
abnormalities in 20% of scans. [74] No correlative clinical data were presented, and
technical limitations were likely to limit any conclusions that may be drawn from
their findings.
A major limitation of all studies using imaging techniques to detect and assess
brain injury is that they were all cross-sectional, and it cannot be determined
whether any abnormalities present were as a result of or preceded participation in
boxing. Further, the findings of studies in young, active boxers, appears to indicate
that evidence of neurological damage as a result of boxing in these younger age
groups is limited (potentially due to the smaller amounts of exposure experienced
by these samples). [70, 71]
6.10.2 Biochemical Markers of CTE
Three studies have concentrated on measuring the concentrations of particular substrates
in the blood before and after an exercise bout. One of the most commonly
measured substrates is creatine kinase isoenzyme BB (CK-BB), which is found in
high concentration in the brain, but blood levels are normally quite low. The hypothesis
was that if higher levels of this substrate were found in the blood after boxingrelated
activities, it may indicate brain injury through disruption of the blood–brain
barrier. Other markers that have been measured include cardiac muscle-specific
creatine kinase (CK-MB); neuron-specific enolase (NSE); and N -acetylaspartate
(NAA) concentrations. When compared to cyclists and oarsmen, serum levels of
CK-BB and NSE were significantly increased in boxers after a bout ( p < 0.01, and
p < 0.02, respectively). [75, 76[ This was shown in one study to be significantly
correlated with an increasing number of blows to the head ( p < 0.05). [75] No elevation
in CK-MB levels was found. [76] For NAA concentration, all three boxers’
studies showed reductions in the absolution concentration compared with both
Parkinson’s patients and age-matched controls. [77]
6.10.3 Neurophysiological Evidence of CTE
Neurophysiological studies have shown variable results. EEG is commonly used as
a diagnostic tool for assessment of brain injury in boxers. [25] EEG assessments,
while often used as part of a pre-participation screening tool by boxing authorities,
have not been shown to be a consistent measure of boxing-related CTE. [46]