Altered Relationship between Working Memory and Brain Microstructure after Mild Traumatic Brain Injury.

BACKGROUND AND PURPOSE: Working memory impairment is one of the most troubling and persistent symptoms after mild traumatic brain injury (MTBI). Here we investigate how working memory deficits relate to detectable WM microstructural injuries to discover robust biomarkers that allow early identification of patients with MTBI at the highest risk of working memory impairment. MATERIALS AND METHODS: Multi-shell diffusion MR imaging was performed on a 3T scanner with 5 b-values. Diffusion metrics of fractional anisotropy, diffusivity and kurtosis (mean, radial, axial), and WM tract integrity were calculated. Auditory-verbal working memory was assessed using the Wechsler Adult Intelligence Scale, 4th ed, subtests: 1) Digit Span including Forward, Backward, and Sequencing; and 2) Letter-Number Sequencing. We studied 19 patients with MTBI within 4 weeks of injury and 20 healthy controls. Tract-Based Spatial Statistics and ROI analyses were performed to reveal possible correlations between diffusion metrics and working memory performance, with age and sex as covariates. RESULTS: ROI analysis found a significant positive correlation between axial kurtosis and Digit Span Backward in MTBI (Pearson r = 0.69, corrected P = .04), mainly present in the right superior longitudinal fasciculus, which was not observed in healthy controls. Patients with MTBI also appeared to lose the normal associations typically seen in fractional anisotropy and axonal water fraction with Letter-Number Sequencing. Tract-Based Spatial Statistics results also support our findings. CONCLUSIONS: Differences between patients with MTBI and healthy controls with regard to the relationship between microstructure measures and working memory performance may relate to known axonal perturbations occurring after injury.

Measurement of problem-solving deficits in adults with acquired brain damage.

OBJECTIVE: To compare the relative utility of conventional neuropsychological and social problem-solving approaches to measuring functional problem solving deficits in individuals with acquired brain damage (ABD). DESIGN: In Study I, scores for individuals with ABD were compared to scores for control and normative samples. In Study II, pre- and posttest scores were compared for individuals with ABD who completed a program of outpatient cognitive rehabilitation. PARTICIPANTS: In Study I, individuals with ABD were compared to healthy controls. In Study II, pre- and posttreatment assessments were obtained for 34 individuals with ABD. MAIN OUTCOME MEASURES: Two approaches were used, conventional neuropsychological (WAIS-R/II Comprehension subtest and Wisconsin Card Sorting Test) and social problem solving (Problem Solving Inventory and Rusk Problem Solving Role Play Test). RESULTS: In Study I, the ABD group demonstrated significant deficits on both social problem solving measures; however, neither conventional neuropsychological measure detected significant deficits in the ABD group, relative to control and normative groups. In Study II, significant treatment gains were demonstrated on both social problem-solving measures, however neither conventional neuropsychological measure was sensitive to improvements in functional problem-solving ability. CONCLUSIONS: In higher-level cognitive rehabilitation settings, the evaluation of functional problem-solving deficits in individuals with ABD can be facilitated by augmenting neuropsychological test data with results from social problem-solving measures.