Glenn Curtiss

Factors moderating neuropsychological outcomes following mild traumatic brain injury: A meta-analysis

There continues to be debate about the long-term neuropsychological impact of mild traumatic brain injury (MTBI). A meta-analysis of the relevant literature was conducted to determine the impact of MTBI across nine cognitive domains. The analysis was based on 39 studies involving 1463 cases of MTBI and 1191 control cases. The overall effect of MTBI on neuropsychological functioning was moderate (d = .54). However, findings were moderated by cognitive domain, time since injury, patient characteristics, and sampling methods. Acute effects (less than 3 months postinjury) of MTBI were greatest for delayed memory and fluency (d = 1.03 and .89, respectively). In unselected or prospective samples, the overall analysis revealed no residual neuropsychological impairment by 3 months postinjury (d = .04). In contrast, clinic-based samples and samples including participants in litigation were associated with greater cognitive sequelae of MTBI (d = .74 and .78, respectively at 3 months or greater). Indeed, litigation was associated with stable or worsening of cognitive functioning over time. The implications and limitations of these findings are discussed.

Long-term neuropsychological outcomes following mild traumatic brain injury.

Mild traumatic brain injury (MTBI) is common, yet few studies have examined neuropsychological outcomes more than 1 year postinjury. Studies of nonreferred individuals with MTBI or studies with appropriate control groups are lacking, but necessary to draw conclusions regarding natural recovery from MTBI. We examined the long-term neuropsychological outcomes of a self-reported MTBI an average of 8 years postinjury in a nonreferred community-dwelling sample of male veterans. This was a cross-sectional cohort study derived from the Vietnam Experience Study. Three groups matched on premorbid cognitive ability were examined, those who (1) had not been injured in a MVA nor had a head injury (Normal Control; n = 3214), (2) had been injured in a motor vehicle accident (MVA) but did not have a head injury (MVA Control; n = 539), and (3) had a head injury with altered consciousness (MTBI; n = 254). A MANOVA found no group differences on a standard neuropsychological test battery of 15 measures. Across 15 measures, the average neuropsychological effect size of MTBI compared with either control group was -.03. Subtle aspects of attention and working memory also were examined by comparing groups on Paced Auditory Serial Addition Test (PASAT) continuation rate and California Verbal Learning Test (CVLT) proactive interference (PI). Compared with normal controls, the MTBI group evidenced attention problems in their lower rate of continuation to completion on the PASAT (odds ratio = 1.32, CI = 1.0-1.73) and in excessive PI (odds ratio = 1.66, CI = 1.11-2.47). Unique to the MTBI group, PASAT continuation problems were associated with left-sided visual imperceptions and excessive PI was associated with impaired tandem gait. These results show that MTBI can have adverse long-term neuropsychological outcomes on subtle aspects of complex attention and working memory.

Long-term morbidities following self-reported mild traumatic brain injury.

The objective of this study was to examine the prevalence of long-term psychiatric, neurologic, and psychosocial morbidities of self-reported mild traumatic brain injury (MTBI). A cross-sectional cohort sample of three groups was examined: those who had not been injured in a motor vehicle accident nor had a MTBI (n = 3,214); those who had been injured in an accident but did not have a MTBI (n = 539); and those who had a MTBI with altered consciousness (n = 254). Logistic regression analyses were used to model odds ratios for the association between group and outcome variables while controlling demographic characteristics, comorbid medical conditions, and early-life psychiatric problems. Compared with uninjured controls, MTBI increased the likelihood of depression and postconcussion syndrome. MTBI also was associated with peripheral visual imperceptions and impaired tandem gait. Similarly, the MTBI group had poorer psychosocial outcomes including an increased likelihood of self-reported disability, underemployment, low income, and marital problems. Results suggest that MTBI can have adverse long-term psychiatric, neurologic, and psychosocial morbidities.

The effects of depression and anxiety on memory performance

The effects of depression and anxiety, as assessed by MMPI D and Pt scales, on memory performance was examined in 3999 veterans who completed the California Verbal Learning Test (CVLT). Depressive symptoms (without anxiety) had an adverse effect on immediate recall of new information and the total amount (but not rate) of acquisition; however, retrieval and retention were unaffected. On the other hand, high levels of anxiety did not have significant detrimental effects on any aspect of memory functioning assessed including immediate recall, total amount acquired, retention, and retrieval of novel information. However, when depression was compounded by anxiety, there was not only an adverse effect on immediate recall and amount (but not rate) of acquisition, but also on the retrieval of newly learned information. We conclude that the presence of comorbid anxiety may, in part, account for the variability in previous research findings regarding the effects of depression on memory functioning.

Rehabilitation of traumatic brain injury in active duty military personnel and veterans: Defense and Veterans Brain Injury Center randomized controlled trial of two rehabilitation approaches.

OBJECTIVES To determine the relative efficacy of 2 different acute traumatic brain injury (TBI) rehabilitation approaches: cognitive didactic versus functional-experiential, and secondarily to determine relative efficacy for different patient subpopulations. DESIGN Randomized, controlled, intent-to-treat trial comparing 2 alternative TBI treatment approaches. SETTING Four Veterans Administration acute inpatient TBI rehabilitation programs. PARTICIPANTS Adult veterans or active duty military service members (N=360) with moderate to severe TBI. INTERVENTIONS One and a half to 2.5 hours of protocol-specific cognitive-didactic versus functional-experiential rehabilitation therapy integrated into interdisciplinary acute Commission for Accreditation of Rehabilitation Facilities-accredited inpatient TBI rehabilitation programs with another 2 to 2.5 hours daily of occupational and physical therapy. Duration of protocol treatment varied from 20 to 60 days depending on the clinical needs and progress of each participant. MAIN OUTCOME MEASURES The 2 primary outcome measures were functional independence in living and return to work and/or school assessed by independent evaluators at 1-year follow-up. Secondary outcome measures consisted of the FIM, Disability Rating Scale score, and items from the Present State Exam, Apathy Evaluation Scale, and Neurobehavioral Rating Scale. RESULTS The cognitive-didactic and functional-experiential treatments did not result in overall group differences in the broad 1-year primary outcomes. However, analysis of secondary outcomes found differentially better immediate posttreatment cognitive function (mean+/-SD cognitive FIM) in participants randomized to cognitive-didactic treatment (27.3+/-6.2) than to functional treatment (25.6+/-6.0, t332=2.56, P=.01). Exploratory subgroup analyses found that younger participants in the cognitive arm had a higher rate of returning to work or school than younger patients in the functional arm, whereas participants older than 30 years and those with more years of education in the functional arm had higher rates of independent living status at 1 year posttreatment than similar patients in the cognitive arm. CONCLUSIONS Results from this large multicenter randomized controlled trial comparing cognitive-didactic and functional-experiential approaches to brain injury rehabilitation indicated improved but similar long-term global functional outcome. Participants in the cognitive treatment arm achieved better short-term functional cognitive performance than patients in the functional treatment arm. The current increase in war-related brain injuries provides added urgency for rigorous study of rehabilitation treatments. (http://ClinicalTrials.gov ID# NCT00540020.).

Verbal Learning and Memory Deficits in Traumatic Brain Injury: Encoding, Consolidation, and Retrieval

The present study examined the nature of verbal memory deficits in individuals with traumatic brain injury (TBI) compared to healthy controls. The study was designed to control for methodological shortcomings of previous related research. Three groups of participants were used: (a) a head injured sample with moderate to severe traumatic brain injuries (N=55), (b) a control sample matched on age and initial performance on CVLT Trial 5 and Sum of Trials 1 to 5 (N=55), and (c) a control sample matched on age, education, and race, but not on initial CVLT learning performance (N=55). Current findings indicate that: (a) rate of learning was comparable across groups, consistent with no encoding differences, (b) TBI patients have a significantly more rapid rate of forgetting of new information than either acquisition-matched or demographic-matched controls, consistent with consolidation problems in TBI, (c) TBI patients have less proactive interference than demographic-matched control participants, consistent with a consolidation problem in the TBI group, (d) TBI patients and acquisition-matched controls have comparably low rates of proactive interference, consistent with impaired acquisition in both of these groups, and (e) TBI patients and controls do not differ in the benefit experienced from semantic or recognition retrieval cues, consistent with no differences in retrieval processes. These data support an impaired consolidation hypothesis, rather than encoding or retrieval deficits, as the primary deficit underlying memory impairment in TBI.

Construct validity of various verbal and visual memory tests

Factor analysis was conducted on attention, information processing, verbal and visual memory scores of 112 patients. Factor structure did not vary as a function of age. The Expanded Paired Associates Test, Verbal Selective Reminding Test, Continuous Recognition Memory Test, and Continuous Visual Memory Test defined a general memory factor. The PASAT, WMS Mental Control, and WAIS-R Digit Span defined an attention/information processing factor. Immediate Visual Reproduction (VR) loaded primarily on visual/nonverbal intelligence, whereas delayed VR loaded primarily with the memory factor. The Trail Making Test, Part B was more closely associated with visual/nonverbal intelligence than with attention/information processing. Serial Digit Learning was more closely associated with attention/information processing than with general memory.

The Components of Executive Functioning in Traumatic Brain Injury

Theorists have proposed models of executive functioning, and functional neuroimaging and factor analytic studies have attempted to examine the components of executive functioning. These studies have arrived at different conclusions and many empirical studies are wrought with methodological confounds. The purpose of this exploratory study was to investigate the subcomponents of executive abilities while addressing some of the limitations common in previous studies. Neuropsychological test data were obtained from a sample of individuals with a history of TBI seen at one-year follow-up (n=104). Principal components factor analysis was conducted and yielded three factors that accounted for 52.7% of the variance. The first factor included higher-order executive functions with two components: self-generative behavior and cognitive flexibility/set shifting. The second factor appeared to represent mental control, particularly of ongoing working memory. The third factor consisted of memory errors, representing failure to inhibit reporting of inaccurate information. Although the results are not entirely consistent with any of the current theoretical models of executive function, they appear to be most consistent with the 1986 model of Stuss and Benson. This research was supported in part by the Department of Veterans’ Affairs and by the Defense and Veterans’ Brain Injury Center. Portions of this paper were presented at the 111th Annual Meeting of the American Psychological Association, Toronto, August, 2003. The first author, Robyn Busch, Ph.D., is now at The Cleveland Clinic Foundation, Department of Psychiatry and Psychology, Cleveland, OH and the second author, Angela McBride, Ph.D., is now at the University of South Florida, Department of Psychiatry.

Predictors of postconcussion symptom complex in community dwelling male veterans.

The presence of a persistent postconcussion symptom complex (PPCSC) was examined in a non-referred sample of male veterans with a history of mild head injury and a comparison group without a history of head injury. Hierarchical logistic regression procedures were used to determine possible predictors of PPCSC using variables supported by previous research (i.e., preexisting psychiatric difficulties, demographic and social support variables, and history of an accidental injurious event). Although PPCSC was common in all groups (23% of the total sample), a significantly greater proportion of individuals in the mild head injury with loss of consciousness group (37.2%) had PPCSC compared with three other groups (head injury without loss of consciousness = 26.1%; motor vehicle accident without head injury = 23%; and control = 17.3%). However, the most salient predictors of PPCSC were early life psychiatric difficulties such as anxiety or depression, limited social support, lower intelligence, and interactions among these variables. The predictive value of loss of consciousness was significant, but low (1.4% of unique variance). The findings provide support for the premise that PPCSC is mediated in part by individual resilience, preexisting psychological status, and psychosocial support.

Discriminability of the Wisconsin Card Sorting Test using the standardization sample.

The four neurological patient groups and the normals from the Wisconsin Card Sorting Test (WCST) standardization sample were used to examine the discriminability of the WCSTs indices. Results reveal consistent differentiation of normals from the patient groups on all WCST variables, with classification rates averaging 71% accuracy. However, patient groups with frontal, diffuse, and nonfrontal lesions were not consistently discriminable from each other. The results suggest that the WCST is most usefully conceptualized as a measure of executive abilities that involves the frontal lobes, but should not be considered solely as a marker of isolated frontal lobe pathology.