No visible differences appeared when viewing the results in FSLview. T tests were performed using the previously mentioned contrast images as statistical maps, overlaid across the brain template. Based on the t tests performed, there was no evidence to support differences in cortical thickness between TBI and OI groups in either direction (p = 0.05).
Discussion
The results failed to support the hypothesis, and cortices of TBI participants were not, in fact, significantly thinner than those of OI control participants. These findings stand in contrast to conclusions drawn from previous studies. Several confounding variables may exist, however, and could have reasonably made contributions to the null effect observed here. For example, injury severity has been identified as a key factor in some brain structure outcomes. One study found that the severity of injury strongly predicted not only short term structural damage, but also long term recovery of white matter among pediatric participants (Genc et al, 2017). Perhaps a similar phenomenon could occur in recovery of cortical thickness, and thus a lack of injury severity may be hindering the ability to differentiate between OI and TBI patients. In future studies, a wider spectrum of injury severities should be examined.
Elapsed time since the incidence of injury also seems to be a critical factor in pediatric cortical thickness. In one study comparing pediatric TBI and OI patients, for example, TBI patients exhibited cortical thinning at 3 months post injury in superior frontal, dorsolateral frontal, orbital frontal, and anterior cingulate regions of the cortex. At an 18 month follow up, additional regions of cortical thinning emerged. However, some regions originally identified as exhibiting cortical thickness now no longer were statistically different from controls (Wilde, 2012). It is possible that images in the present study were merely obtained at a time where cortical thickness had rebounded to some degree in TBI patients, and naturally thinned among OI patients. The respective thickness of both participant groups is subject to fluctuate however, and may feasibly cross over at some points. This could contribute to the null effect currently observed, which may be obscuring a significant effect that can only be tracked longitudinally. The acute nature of this study, therefore, may be a serious limitation.
While no effect was observed in this study, the literature remains inconclusive. Extensions of this study, including more severely injured patients followed longitudinally, may prove useful in establishing the true relationship between TBI and cortical thickness.
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