Abstract
Although a proportion of individuals report chronic cognitive difficulties after mild traumatic brain injury (mTBI), results from behavioral testing have been inconsistent. In fact, the variability inherent to the mTBI population may be masking subtle cognitive deficits. We hypothesized that this variability could be reduced by accounting for post-concussion syndrome (PCS) in the sample. Thirty-six participants with mTBI (>1 year post-injury) and 36 non-head injured controls performed information processing speed (Paced Visual Serial Addition Task, PVSAT) and working memory (n-Back) tasks. Both groups were split by PCS diagnosis (4 groups, all n = 18), with categorization of controls based on symptom report. Participants with mTBI and persistent PCS had significantly greater error rates on both the n-Back and PVSAT, at every difficulty level except 0-Back (used as a test of performance validity). There was no difference between any of the other groups. Therefore, a cognitive deficit can be observed in mTBI participants, even 1 year after injury. Correlations between cognitive performance and symptoms were only observed for mTBI participants, with worse performance correlating with lower sleep quality, in addition to a medium effect size association (falling short of statistical significance) with higher PCS symptoms, post-traumatic stress disorder (PTSD), and anxiety. These results suggest that the reduction in cognitive performance is not due to greater symptom report itself, but is associated to some extent with the initial injury. Furthermore, the results validate the utility of our participant grouping, and demonstrate its potential to reduce the variability observed in previous studies.
Highlights
MTBI + post-concussion syndrome (PCS) participants reported a greater number of post-traumatic stress disorder (PTSD) symptoms compared to mild traumatic brain injury (mTBI) − PCS participants (p = 0.009)
Working memory and information processing speed was significantly impaired in mTBI participants with persistent PCS compared to mTBI participants without PCS and all non-head injured participants
Correlations between cognitive performance and symptoms were only observed for mTBI participants, with worse performance correlating with lower sleep quality, in addition to medium effect size associations with higher PCS symptoms, PTSD, and anxiety
Summary
A number of studies report that mild traumatic brain injury (mTBI) participants have reduced cognitive performance, even in the long-term (>3 months) after injury, on tasks that assess attention (Mangels et al, 2002; Chan, 2005; Kumar et al, 2005; Sterr et al, 2006; Catale et al, 2009; Maruta et al, 2010), memory (Vanderploeg et al, 2005; Chen et al, 2007; Catale et al, 2009), executive function (O’Jile et al, 2006; Sterr et al, 2006; Erez et al, 2009; Pontifex et al, 2009), and information processing (O’Jile et al, 2006; Lachapelle et al, 2008; Johansson et al, 2009; Kinnunen et al, 2011). There is research that observes no deficit in cognitive performance in mTBI patients in the long-term (Chen et al, 2004; Perlstein et al, 2004; Solbakk et al, 2005; Broglio et al, 2009; Tellier et al, 2009) or within the 3 months following injury (McAllister et al, 2001; Chen et al, 2004; Jantzen et al, 2004; Lange et al, 2009; Tellier et al, 2009; Slobounov et al, 2010). Of particular utility in this regard are tasks that can be parametrically increased in difficulty (Braver et al, 1997; Pare et al, 2009), enabling an investigation of the effects of enhancing cognitive load
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