Cognitive test performances related to early and late computed tomography findings after closed-head injury

Cross-validation of incidental learning tasks from the WAIS-IV as a measure of memory

Although incidental learning (IL) routinely occurs in everyday life, it is infrequently assessed during neuropsychological evaluations. This study aimed to further examine the concurrent validity of IL measures based on the Vocabulary and Similarities subtests from the Wechsler Adult Intelligence Test-Fourth Edition (WAIS-IV). Participants included 43 Veterans referred for outpatient neuropsychological testing. Performances on the IL procedures correlated strongly with performances on the Repeatable Battery for the Assessment of Neuropsychological Status Immediate and Delayed Recall Indices (r = .48 to r = .78). These results indicate that the IL procedures from selected WAIS-IV subtests provided an efficient and valid measure of memory. In particular, the task based on the Similarities subtest provided exceptionally high value as a screen for memory problems. These IL procedures, which require minimal additional administration time, capitalize on the semantic encoding that is inherent in completing the Vocabulary and Similarities subtests, and offer a complementary approach to standard memory assessment.

An exploratory study of the use of the Wechsler Digit-Symbol Incidental Learning procedure with the WAIS-IV

The Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV) does not include the optional Incidental Learning procedure for the Digit-Symbol subtest (now simply called Coding) that had been available in the WAIS-Third Edition (WAIS-III). However, the procedure itself has been shown to have some utility in assessment of incidental memory processes. The current study of a mixed clinical outpatient sample (n = 75) sought to identify salient characteristics of the Incidental Learning tasks as applied to WAIS-IV Coding. Findings showed that the Pairing procedure, when applied to the WAIS-IV, has different characteristics than it did with the WAIS-III; it is more difficult overall, and different items tend to be more prominently recalled than others. The Free Recall procedure for the WAIS-IV is comparable to the WAIS-III version in overall difficulty. Implications and implementation of the current findings are discussed.

Attentional control and slowness of information processing after severe traumatic brain injury

Attention is a basic cognitive function and a prerequisite for other cognitive processes and is frequently impaired after traumatic brain injury. In the present study, 29 severe traumatic brain injury patients and 30 control subjects completed a battery of three neuropsychological tests of attention (WCST, TMT, Stroop). The aim was to clarify the attentional mechanisms underlying tests performance and to explore the types of attentional impairment after severe traumatic brain injury. Significant differences were found between the control and clinical groups in almost all measures. However, some of these differences disappeared when the speed of information processing was controlled using covariance analysis. In addition, a factor analysis revealed a four-factor solution explaining 89.6% of the variance in the data, i.e. cognitive flexibility, speed of processing, interference and working memory. This result supports the view of at least four different subprocesses of attentional control underlie test performance and allows one to differentiate between high- and low-level processes. The implications for neuropsychological assessment and rehabilitation are discussed.

Relationship of the Met allele of the brain-derived neurotrophic factor Val66Met polymorphism to memory after aneurysmal subarachnoid hemorrhage

OBJECTIVE

The brain-derived neurotrophic factor (BDNF) Val66Met polymorphism has been shown to be related to variability in episodic memory. We studied whether the Met allele is associated with poor learning and memory in survivors of aneurysmal subarachnoid hemorrhage (SAH).

METHODS

Ninety-six patients were examined with a neuropsychological test battery approximately 1 year after SAH. Their deoxyribonucleic acid samples were genotyped for the BDNF Val66Met polymorphism. The Met carriers were compared to the Val/Val homozygous patients on the test performances.

RESULTS

In the total sample, there was no difference between the genotype groups. However, among the patients with no cerebral infarction, the Met carriers had inferior learning and memory performance than the Val/Val homozygotes, but the groups did not differ on the nonmemory test performances. The patients with left and bilateral infarctions had deficits in verbal memory, which may have concealed the effect of the BDNF Val66Met polymorphism on memory in the total sample.

CONCLUSION

As a whole, the BDNF Val66Met polymorphism was not associated with learning and memory performance in patients recovering from SAH. However, the Met allele might predict poor memory function among patients with SAH not complicated by a cerebral infarction. These findings support earlier reports of an association between the Met allele and low memory performance. Longitudinal studies comparing functional recovery from SAH between Met and Val/Val patients without cerebral infarctions are warranted.

Memory functions in recreational pistol sport shooters: does lead matter?

OBJECTIVE

The aim of our study was to examine the memory functions of pistol sport shooters using powder charges when exposure to lead is expected to be considerably lower than in occupational circumstances.

METHODS

A neuropsychological battery of memory and intelligence tests was administered to 20 sport shooters and 20 controls whose mean ages (SDs) were 55 (9.6) and 54 (9.3) years respectively. Memory functions were evaluated with three subtests of the Wechsler Memory Scale - Revised (WMS-R) and an incidental memory test. Intelligence was assessed with four subtests of the Wechsler Adult Intelligence Scale - Revised (WAIS-R). The level of alcohol consumption and depression were examined in both groups. Blood lead level was determined among the shooters.

RESULTS

The shooters performed worse than the controls in the tests of incidental and logical memory. The groups did not differ in intelligence, mood or alcohol consumption. The mean (SD) blood lead level of the sport shooters was 0.52 mumol/L (0.40), responding 10.76 mug/dl (8.28).

CONCLUSIONS

Low lead exposure in recreational shooting conditions may impair verbal memory. Therefore it is important to ensure that lead exposure is prevented among those shooting for sport.

Computed tomography findings and early cognitive outcome after traumatic brain injury

PRIMARY OBJECTIVE

To examine the relationship between CT abnormalities and early neuropsychological outcome following traumatic brain injury (TBI) using quantitative CT analyses, data reduction methods for neuropsychological results and specific hypotheses based on literature review.

RESEARCH DESIGN

Observational, prospective cohort study using acute (emergency) CT data and neuropsychological test data from 89 participants with TBI who were hospitalized for rehabilitation.

METHODS AND PROCEDURES

Principal components analysis with varimax rotation was used to reduce data from a standard battery of eight neuropsychological tests administered after clearance of post-traumatic amnesia (1 month post-TBI on average). Bivariate correlations were used to examine relationships of three factors (verbal memory, cognitive processing speed and verbal working memory) to quantitative volumetric analysis of CT scan abnormalities (size, number and location). Specific hypotheses as to CT predictors of poor performance on each factor were tested using multivariable linear regression that included injury severity and demographic variables.

MAIN RESULTS

Eighty-nine per cent of participants had some pathology on initial CT. Age, education and time to follow commands (TFC), an index of overall injury severity, were significantly associated with the neuropsychological factors. However, none of the specific hypotheses about CT scan variables and cognitive outcome were strongly supported by the data. There was a trend for any CT abnormality to predict slower speed of processing and for higher number of brain lesions to predict worse memory performance.

CONCLUSIONS

Despite the precision added by quantitative CT analysis, CT findings did not improve on demographic factors and TFC in predicting early cognitive outcome of TBI. Imaging methods that are more sensitive to white matter integrity may be needed to develop pathophysiologic predictors of TBI outcome.

Relationship of Local Infarctions to Cognitive and Psychosocial Impairments after Aneurysmal Subarachnoid Hemorrhage

OBJECTIVE:

Previous studies suggest that cognitive and psychosocial impairments after subarachnoid hemorrhage (SAH) result from diffuse brain damage caused by the initial bleeding rather than from focal lesions. We describe the relationship of local infarctions to these impairments and explore how well test and questionnaire results explain psychosocial outcome.

METHODS:

A total of 170 patients, selected from a consecutive series of patients with aneurysmal SAH, underwent neurological and neuroradiological examinations, and 138 of them were assessed with neuropsychological tests and questionnaires 1 year after SAH.

RESULTS:

Patients with left and bilateral infarctions performed worse on verbal memory tests than the other patients, and patients with left infarctions had more impaired working capacity than those with no infarction. The indices of the severity of SAH were related to reductions in both working capacity and social activity but less clearly to poor test performances. Whereas the modified Rankin scale was the most important correlate of working capacity, performance on cognitive tests was associated with return to work, and questionnaire ratings of mental impairments correlated with reduced working capacity and decreased social activity.

CONCLUSION:

Left-hemisphere infarctions cause deficits in verbal memory and working capacity. The severity of SAH is associated with impairments in working capacity and social activity rather than with specific cognitive deficits. Patients' and partners' opinions on patients' mental impairments could provide complementary information to clinical grades and cognitive tests in the evaluation of outcome after SAH.

The role of prefrontal cortex in working-memory capacity, executive attention, and general fluid intelligence: an individual-differences perspective

We provide an "executive-attention" framework for organizing the cognitive neuroscience research on the constructs of working-memory capacity (WMC), general fluid intelligence, and prefrontal cortex (PFC) function. Rather than provide a novel theory of PFC function, we synthesize a wealth of single-cell, brain-imaging, and neuropsychological research through the lens of our theory of normal individual differences in WMC and attention control (Engle, Kane, & Tuholski, 1999; Engle, Tuholski, Laughlin, & Conway, 1999). Our critical review confirms the prevalent view that dorsolateral PFC circuitry is critical to executive-attention functions. Moreover, although the dorsolateral PFC is but one critical structure in a network of anterior and posterior "attention control" areas, it does have a unique executive-attention role in actively maintaining access to stimulus representations and goals in interference-rich contexts. Our review suggests the utility of an executive-attention framework for guiding future research on both PFC function and cognitive control.

Current concepts: diffuse axonal injury-associated traumatic brain injury

OBJECTIVES

To review the probable physical, physiologic mechanisms that result in the medical and neuropsychologic complications of diffuse axonal injury (DAI)-associated traumatic brain injury (TBI).

DATA SOURCES

Various materials were accessed: MEDLINE, textbooks, scientific presentations, and current ongoing research that has been recently reported.

STUDY SELECTION

Included were scientific studies involving TBI, particularly direct injury to the axons and glia of the central nervous system (CNS) in both in vitro and in vivo models. These studies include pathologic findings in humans as well as the medical complications and behavioral outcomes of DAI. Studies that addressed animal models of DAI as well as cellular and/or tissue models of neuronal injury were emphasized. The review also covered work on the physical properties of materials involved in the transmission of energy associated with prolonged acceleration-deceleration injuries.

DATA EXTRACTION

Studies were selected with regard to those that addressed the mechanism of TBI associated with DAI and direct injury to the axon within the CNS. The material was generally the emphasis of the article and was extracted by multiple observers. Studies that correlate the above findings with the clinical picture of DAI were included.

DATA SYNTHESIS

Concepts were developed by the authors based on the current scientific findings and theories of DAI. The synthesis of these concepts involves expertise in physical science, basic science concepts of cellular injury to the CNS, acute medical indicators of DAI, neuropsychologic indicators of DAI, and rehabilitation outcomes from TBI.

CONCLUSIONS

The term DAI is a misnomer. It is not a diffuse injury to the whole brain, rather it is predominant in discrete regions of the brain following high-speed, long-duration deceleration injuries. DAI is a consistent feature of TBI from transportation-related injuries as well as some sports injuries. The pathology of DAI in humans is characterized histologically by widespread damage to the axons of the brainstem, parasagittal white matter of the cerebral cortex, corpus callosum, and the gray-white matter junctions of the cerebral cortex. Computed tomography and magnetic resonance imaging scans taken initially after injury are often normal. The deformation of the brain due to plastic flow of the neural structures associated with DAI explains the micropathologic findings, radiologic findings, and medical and neuropsychologic complications from this type of injury mechanism. There is evidence that the types of cellular injury in TBI (DAI, anoxic, contusion, hemorrhagic, perfusion-reperfusion) should be differentiated, as all may involve different receptors and biochemical pathways that impact recovery. These differing mechanisms of cellular injury involving specific biochemical pathways and locations of injury may, in part, explain the lack of success in drug trials to ameliorate TBI.

Wechsler Adult Intelligence Scale-Revised Block Design broken configuration errors in nonpenetrating traumatic brain injury

Final broken configuration errors on the Wechsler Adult Intelligence Scale-Revised (WAIS-R; Wechsler, 1981) Block Design subtest were examined in 50 moderate and severe nonpenetrating traumatically brain injured adults. Patients were divided into left (n = 15) and right hemisphere (n = 19) groups based on a history of unilateral craniotomy for treatment of an intracranial lesion and were compared to a group with diffuse or negative brain CT scan findings and no history of neurosurgery (n = 16). The percentage of final broken configuration errors was related to injury severity, Benton Visual Form Discrimination Test (VFD; Benton, Hamsher, Varney, & Spreen, 1983) total score and the number of VFD rotation and peripheral errors. The percentage of final broken configuration errors was higher in the patients with right craniotomies than in the left or no craniotomy groups, which did not differ. Broken configuration errors did not occur more frequently on designs without an embedded grid pattern. Right craniotomy patients did not show a greater percentage of broken configuration errors on nongrid designs as compared to grid designs.

Early predictors of mortality and morbidity after severe closed head injury

Mortality and morbidity of 158 patients with severe head injury were studied in relation to age, and early (24-h) clinical and computed tomography data. For comparison of outcome data in survivors, a group of 32 patients with traumatic injuries to parts of the body other than the head was used as controls. Within the head-injured group, the mortality rate was 51%. Logistic regression analyses combined 13 out of 16 predictors into a model with an accuracy of 93%, a sensitivity of 90%, and a specificity of 95%. These include age, Glasgow Coma Scale (GCS) score, pupillary reactivity, blood pressure, intracranial pressure, blood glucose, platelet count, body temperature, cerebral lactate, and subdural, intracranial, subarachnoid, and ventricular hemorrhage. At 6 months postinjury, head-injury survivors and trauma controls were evaluated with the Glasgow Outcome Scale (GOS), a neuropsychological test battery and the Sickness Impact Profile (SIP). Head-injury survivors had a higher proportion of disabilities and neuropsychological dysfunctions than trauma controls. They also report more quality of life-related functional limitations on the SIP scales for mobility, intellectual behavior, communication, home management, eating, and work. Linear regression analysis resulted in age being the only important predictor of outcome on the GOS, the GCS score being the best predictor of neuropsychological functioning, and pupillary reactivity being the most predictive for self-reported quality of life as measured by SIP. Those factors important for predicting mortality (clinical variables such as ICP or blood glucose level, and CT observations) failed to show any significant relationship with morbidity.

Extracellular lactate and glucose alterations in the brain after head injury measured by microdialysis

OBJECTIVE

To study cerebral glucose and lactate metabolism in head-injured patients using microdialysis.

DESIGN

Prospective, nonrandomized, clinical study.

SETTING

Neurosurgical intensive care unit in a university-affiliated county hospital.

PATIENTS

One hundred twenty-six head-injured patients.

INTERVENTIONS

Cerebral cortical neurochemical monitoring using microdialysis coupled with systemic hemodynamic and oxygenation monitoring, measurement of cerebral perfusion pressure and intracranial pressure, and measurement of global cerebral oxygenation using jugular venous oxygen saturation in all 126 patients. In selected cases, cerebral blood flow was also measured using cortical thermodilution probes in 33 patients, and regional cerebral oxygenation was measured using PO2 probes in 65 patients.

MEASUREMENTS AND MAIN RESULTS

Elevated extracellular lactate, reduced glucose, and an elevated lactate/glucose ratio were observed with cerebral hypoxia and ischemia. Elevated lactate and an increased lactate/glucose ratio strongly correlated with death. Other more subtle alterations of lactate and glucose were seen early after injury that may reflect compensatory alterations in cerebral metabolism.

CONCLUSIONS

Clinical neurochemical monitoring of glucose and lactate levels in the extracellular space of the cerebral cortex is technically feasible and provides insight into the bioenergetic status of the brain. Increased lactate and decreased glucose, indicating accelerated glycolysis, commonly occurred with cerebral ischemia or hypoxia, and increased anaerobic glycolysis in this setting is associated with a poor outcome.

Procedural learning is impaired in patients with prefrontal lesions

OBJECTIVES

To 1) determine the effect of prefrontal cortex lesions on procedural learning (PL), measured by a serial reaction-time task (SRTT); 2) confirm whether visuomotor PL is lateralized to one hemisphere; and 3) clarify the relation between visuomotor sequence learning and verbal sequence learning, working memory, and executive functions.

BACKGROUND

Previous cognitive neuroscience research has implicated the prefrontal cortex in visuomotor PL but there is a lack of studies examining patients with prefrontal cortex lesions.

METHODS

We studied 22 patients with strictly unilateral prefrontal cortex lesions (traumatic, ischemic, hemorrhagic, or tumors) and 52 cognitively intact controls matched for age, sex, and educational level. We administered to subjects long (10-item sequence) and short (4-item sequence) versions of the SRTT. With the long version, each hand was evaluated separately. Learning was indicated by the shortening of response times (RT) and decrease in errors across the sequential blocks and, most importantly, the rebound increase in RTs and errors when comparing the last sequence block with the next random block. Frontal lobe functions and verbal sequence learning were also assessed.

RESULTS

Patients with unilateral prefrontal cortex lesions show PL impairment that involves both hands, although more errors were observed when the hand contralateral to the lesion was performing. Only those patients whose lesions were >2 cm in diameter were impaired. Neuropsychologic evaluation indicated impaired verbal sequence learning and executive function deficits. Patients with poorer working memory and verbal sequence learning were also more impaired in visuomotor sequence learning.

CONCLUSIONS

The prefrontal cortex has a role in PL and is part of the neural circuit that mediates this type of learning.

Executive dysfunction and characterological changes after traumatic brain injury: two sides of the same coin?

This study examined the capacity of neuropsychological variables indicative of dysfunction in the regulation of executive abilities (e.g. noncompliance with rules) to reflect changes in character associated with disturbances in regulatory abilities (e.g. impulsivity). A close relative of 30 participants with traumatic brain injury (TBI) was administered the Current Behaviour Scale (CBS) at admission (rating premorbid character) and six months posttrauma (rating current character). The TBI group was examined neuropsychologically at six months posttrauma, along with 30 nonbrain-damaged (NBD) participants. Significant increases in CBS factors, Loss of Emotional Control and Loss of Motivation, occurred in the TBI group posttrauma. Differences between TBI and NBD groups were found for most executive variables. Those TBI participants with impairments on the neuropsychological Rule Breaking variable showed significant posttrauma increases in Loss of Emotional Control. There was also a trend for individuals with frontal lesions to make rule-breaking and perseverative errors.

Cognitive-linguistic subgroups in closed-head injury

This study examined variability in the interrelationship between language skill and neuropsychological function within a group of 25 severe closed head injury (CHI) subjects and 23 matched controls. All subjects underwent a battery of standardized language and neuropsychological tests. Cluster analyses were conducted to determine whether the CHI sample was universally or differentially impaired. Further subgroup analysis using a Q-type factor analysis outlined the differences in performance profiles within the group of CHI subjects. Results support the hypothesis that while some deficits were common to all CHI subjects, impairments delineated by whole group analysis do not necessarily represent universal impairments. In particular, ability to perform tasks involving auditory comprehension, naming, verbal memory, visual memory and visuospatial skills appeared to be important components in group differentiation. The cognitive-linguistic impairments which were common to all CHI subjects and considered to be the 'cardinal' cognitive-linguistic deficits following severe CHI were deficits in lexical-semantic and sentential semantic skills, verbal fluency, complex auditory comprehension, and attentional operations. Profile analysis revealed the existence of a double dissociation between performances on naming and verbal memory tasks and performances on visually related cognitive tasks. Results are discussed with reference to findings on previous studies of subgroups in the CHI population.

Extent of cognitive decline in traumatic brain injury based on estimates of premorbid intelligence

Global cognitive impairment following traumatic brain injury (TBI) is common, with some abilities more significantly affected than others. However, due to difficulties in estimating premorbid intelligence, there has been no systematic evaluation of the extent of decline in different cognitive abilities following TBI. Recent studies indicate that the Wide Range Achievement Test-Revised (WRAT-R) Reading subtest is an accurate estimate of premorbid intelligence, suggesting that post-TBI cognitive test scores can be compared to the WRAT-R to estimate the extent of decline that occurs in specific cognitive abilities. The current study estimated the extent of deficit in intelligence, memory, attention, speed of processing, and cognitive flexibility for 97 outpatients with TBI. Extent of decline was calculated by subtracting WRAT-R z-scores from cognitive test z-scores to determine a z-difference score (ZDiff) for each cognitive ability. The results suggest that intelligence is least declined following TBI (WAIS-R 3-4-point decline; VIQ ZDiff = -0.23: FIQ ZDiff = -0.27), followed by attention (WMS-R 5-point decline; ZDiff = -0.31), memory (WMS-R 6-9-point decline; Verbal Memory ZDiff = -0.41; General Memory ZDiff = -0.51; Delay Memory ZDiff = -0.57), speed of processing (Trails A 15-16 second decline; ZDiff = -1.90) and cognitive flexibility (Trails B 35-52 second decline; ZDiff = -2.65). Implications for provision of feedback to individuals with TBI and their families are discussed.

Neuropsychological outcome and quantitative image analysis of acute haemorrhage in traumatic brain injury: preliminary findings

The effect on neuropsychological outcome of the number of acute haemorrhages, lesion volume, and lesion location in traumatic brain injury (TBI) was evaluated. Haemorrhagic lesion volume was associated with severity of injury. However, the number of petechial haemorrhages was not reliably associated with any of the clinical outcome measures. Likewise, despite the use of detailed morphometric methods to quantify volume, the acute lesion size did not significantly relate to neuropsychological sequelae. Furthermore, brain quadrant localization methods did not enhance outcome prediction. These results are discussed in the context of acute lesion analysis contrasted with chronic TBI-induced neuropathological changes associated with neuropsychological outcome.

Prediction of psychosocial recovery after head injury with cognitive tests and neurobehavioral ratings

A series of 53 patients was studied using a battery of tests and a neurobehavioral rating scale on average 4 months after closed-head injury (CHI). Social outcome was assessed 1 year after injury by interviewing a family member. The results supported the hypothesis that tests of flexibility and programming rather than tests of cognitive skills predict psychosocial recovery after CHI. Spatial Learning with Self-Set Goals and Sorting were measures of flexibility and programming. Contrary to expectation, word fluency performance was unrelated to these measures, but was associated with conventional intelligence tests, which did not predict psychosocial recovery. Cognition/Energy deficit on the Neurobehavioral Rating Scale and increased age were useful predictors of poor psychosocial outcome, whereas computed tomography findings or the Glasgow Coma Score were weakly related to the outcome indices. Evidently, cognitive flexibility and mental programming are very important psychological prerequisites of social recovery after CHI.

Day of injury CT scan as an index to pre-injury brain morphology

This study compared the ventricle-to-brain ratio (VBR) of the day-of-injury (DOI) computerized tomogram (CT) in traumatic brain-injured (TBI) patients with post-injury (2 months or greater) magnetic resonance (MR) VBRs in the same patients and in medical control subjects. The DOI VBR did not differ significantly from the medical controls, but both (DOI and medical control VBR) differed significantly from post-injury VBR. Additionally, a case study is presented wherein MR imaging studies were obtained prior to TBI so that a direct comparison of pre-injury to DOI to post-injury changes could be made. In this case the pre-injury and DOI VBRs were within approximately 9% of each other. In contrast, the post-injury VBR demonstrated over a 100% increase in comparison to either the pre-injury or DOI scan. This case and another case are illustrated using three-dimensional image analysis to represent ventricular change over time. These cases, along with the similarity of the DOI VBR with the medical controls, suggests that the DOI VBR can be utilized as an estimate or index of pre-injury ventricle/brain morphology. This will permit the use of DOI CT data for within-subject designs in TBI research that examines the course of degenerative changes over time.

Cognitive flexibility and mental programming after closed head injuries and anterior or posterior cerebral excisions

Cognitive inflexibility and deficient mental programming are specifically related to frontal lobe lesions. The aim was to demonstrate that closed head injury (CHI) patients with brain lesions verified by computed tomography have such cognitive deficits, and are inferior in these respects to patients with posterior cerebral excisions mainly for tumours. This hypothesis was confirmed using a Category Identification and Sorting test as well as a measure of mental programming in a Spatial Learning task. Furthermore, CHI patients who had non-frontal parenchymal lesions were inferior by these measures to patients with posterior excisions. This result suggests that diffuse axonal lesion in CHI causes the deficits similar to those following frontal lobe excision.