Patterns of neuropsychological test performance in subpopulations of mild traumatic brain injury

The purpose of the present study was to expand upon the somewhat limited literature and mixed findings reported regarding the neuropsychological profiles of individuals with complicated mild traumatic brain injury (mTBI). Performance of individuals with complicated and uncomplicated mTBI was compared with neurologically normal controls while controlling for response effort and demographic variables. ^ Participants included in the mTBI groups were seen through a trauma service clinical pathway. Individuals included in the neurologically normal control group were provided by the Psychological Corporation and derived from data obtained during the normative procedure for the Wechsler Adult Intelligence Scale, Third Edition, and the Wechsler Memory Scale, Third Edition. All data is archival in nature. mTBI participants were divided into two groups on the basis of having a normal or abnormal CT scan, and then matched on age, education, ethnicity, and gender with normal control participants. The final sample consisted of 99 patients, with 21 individuals in the uncomplicated mTBI group, 28 individuals in the complicated mTBI group, and 50 individuals in the control group. ^ All groups demonstrated similar patterns of performance on most aspects of intellectual and memory testing. No WMS-III variable and only the Perceptual Organization Index score and the Matrix Reasoning subtest of the WAIS-III distinguished individuals with complicated mTBI from individuals with uncomplicated mTBI and normal control participants. An unusual finding included a superiority of performance by the uncomplicated mTBI individuals, as compared to the control and complicated mTBI groups, on the Matrix Reasoning subtest. The relatively poorer performance on the POI was maintained when effort was controlled. However, the effect sizes were small three groups could not be differentiated using discriminant function analysis. ^ Results of the current study are consistent with recent literature suggesting similar recovery trajectories for complicated and uncomplicated mild brain injury on several neuropsychological variables, and argue against incorporation of new sub-group classification of complicated or high risk mild traumatic brain injury, given similar outcomes.