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Biomedical subjects

John Whyte

Publications and source records attributed to John Whyte.

At least 19 recordsLinked to original sources
PubMed2006

Measuring sustained attention after traumatic brain injury: differences in key findings from the sustained attention to response task (SART).

Clinical reports after traumatic brain injury (TBI) suggest frequent difficulties with sustained attention, but their objective measurement has proved difficult. In 1997, Robertson and colleagues reported on a new sustained attention assessment tool, the sustained attention to response task (SART). Individuals with TBI were reported to produce more errors of commission on the SART than control participants, and both groups showed a relationship between SART errors and everyday lapses of attention as measured by the cognitive failures questionnaire (CFQ). Although few direct replications of these findings have been reported, the SART has been used widely as a measure of sustained attention in TBI, in normal controls, and in various other clinical samples. As part of a program of research on attention in TBI, we administered the SART and the CFQ to a sample of 34 survivors of moderate to severe TBI and to 35 control participants. CFQ scores reported by significant others showed clear group differences in everyday lapses of attention. Despite this, group differences in SART errors of commission were small and non-significant, and the correlations between SART errors and CFQ scores were small within both groups. Further analyses excluding participants with invalid score profiles, or restricting the analysis to the first performance of the SART failed to alter the results. These findings suggest that more research is needed to establish the validity of the SART as a measure of sustained attention after TBI, and to determine under what circumstances the original findings hold.

Adolescent↗
PubMed2006

Continuous ASL perfusion fMRI investigation of higher cognition: quantification of tonic CBF changes during sustained attention and working memory tasks.

Arterial spin labeling (ASL) perfusion fMRI is an emerging method in clinical neuroimaging. Its non-invasiveness, absence of low frequency noise, and ability to quantify the absolute level of cerebral blood flow (CBF) make the method ideal for longitudinal designs or low frequency paradigms. Despite the usefulness in the study of cognitive dysfunctions in clinical populations, perfusion activation studies to date have been conducted for simple sensorimotor paradigms or with single-slice acquisition, mainly due to technical challenges. Using our recently developed amplitude-modulated continuous ASL (CASL) perfusion fMRI protocol, we assessed the feasibility of a higher level cognitive activation study in twelve healthy subjects. Taking advantage of the ASL noise properties, we were able to study tonic CBF changes during uninterrupted 6-min continuous performance of working memory and sustained attention tasks. For the visual sustained attention task, regional CBF increases (6-12 ml/100 g/min) were detected in the right middle frontal gyrus, the bilateral occipital gyri, and the anterior cingulate/medial frontal gyri. During the 2-back working memory task, significantly increased activations (7-11 ml/100 g/min) were found in the left inferior frontal/precentral gyri, the left inferior parietal lobule, the anterior cingulate/medial frontal gyri, and the left occipital gyrus. Locations of activated and deactivated areas largely concur with previous PET and BOLD fMRI studies utilizing similar paradigms. These results demonstrate that CASL perfusion fMRI can be successfully utilized for the investigation of the tonic CBF changes associated with high level cognitive operations. Increased applications of the method to the investigation of cognitively impaired populations are expected to follow.

Adult↗
PubMed2006

Dimensions of disordered attention in traumatic brain injury: further validation of the Moss Attention Rating Scale.

OBJECTIVES: To investigate the factor structure of disordered attention in moderate to severe, acute traumatic brain injury (TBI) and to use factor analysis and item response theory to further validate and refine an observational rating scale of attention for clinical and research purposes. DESIGN: Multicenter inception cohort. SETTING: Inpatient rehabilitation units. PARTICIPANTS: Patients with TBI (N=372) consecutively admitted to 8 Traumatic Brain Injury Model System centers within 2 weeks prior to observation, who consistently followed commands and who were on stable doses of all psychotropic medications for a 3-day rating period. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: Participants were rated independently by treating occupational and physical therapists at an average of 1 month postinjury on the Moss Attention Rating Scale (MARS), a 45-item, Likert-type scale of attention-related behavior. RESULTS: Exploratory and confirmatory factor analyses revealed 3 correlated factors of disordered attention, interpreted as restlessness/distractibility, initiation, and sustained/consistent attention. Item response (Rasch) analysis was used to eliminate redundant items and to fill gaps in item difficulty. The resulting MARS consists of 22 items that can produce 3 factor scores and a total score that covers the broad construct of disordered attention. CONCLUSIONS: The factor-scored MARS has potential utility as a quantitative observational method with which to assess and study different dimensions of disordered attention in acute TBI, and to monitor change over time and treatment response within these dimensions.

Adolescent↗
PubMed2006

Guidelines for the pharmacologic treatment of neurobehavioral sequelae of traumatic brain injury.

There is currently a lack of evidence-based guidelines to guide the pharmacological treatment of neurobehavioral problems that commonly occur after traumatic brain injury (TBI). It was our objective to review the current literature on the pharmacological treatment of neurobehavioral problems after traumatic brain injury in three key areas: aggression, cognitive disorders, and affective disorders/anxiety/ psychosis. Three panels of leading researchers in the field of brain injury were formed to review the current literature on pharmacological treatment for TBI sequelae in the topic areas of affective/anxiety/ psychotic disorders, cognitive disorders, and aggression. A comprehensive Medline literature search was performed by each group to establish the groups of pertinent articles. Additional articles were obtained from bibliography searches of the primary articles. Group members then independently reviewed the articles and established a consensus rating. Despite reviewing a significant number of studies on drug treatment of neurobehavioral sequelae after TBI, the quality of evidence did not support any treatment standards and few guidelines due to a number of recurrent methodological problems. Guidelines were established for the use of methylphenidate in the treatment of deficits in attention and speed of information processing, as well as for the use of beta-blockers for the treatment of aggression following TBI. Options were recommended in the treatment of depression, bipolar disorder/mania, psychosis, aggression, general cognitive functions, and deficits in attention, speed of processing, and memory after TBI. The evidence-based guidelines and options established by this working group may help to guide the pharmacological treatment of the person experiencing neurobehavioral sequelae following TBI. There is a clear need for well-designed randomized controlled trials in the treatment of these common problems after TBI in order to establish definitive treatment standards for this patient population.

Aggression↗
PubMed2006

Applying evidence standards to rehabilitation research.

OBJECTIVE: To describe evidence grading methods employed in the systematic reviews in this special series of articles. To provide an overview of results of these reviews to critique the quality of rehabilitation research. To identify issues in the application of evidence grading methods to rehabilitation. DESIGN: Conceptual review of evidence-based practice and evidence grading methods. English-language research studies on rehabilitation of persons with spinal cord injury, traumatic brain injury, and burn for the 5-yr period of 1999-2004 were reviewed using methods of the American Academy of Neurology supplemented by Cochrane criteria and summarized. RESULTS: Rehabilitation has a shortage of high-level studies. The number of level 1 treatment studies was quite limited (five in spinal cord injury, 15 in traumatic brain injury, 12 in burn rehabilitation), as was the number of level 2 studies (26, 4, and 2, respectively). Despite the large number of correlational studies published, the number of high-level (1 or 2) diagnostic and prognostic studies was surprisingly limited (34, 11, and 5, respectively). The rate of production of high-level studies is rapidly increasing. Problems were encountered in applying standard evidence criteria to complex issues encountered in some studies, suggesting limitations and issues in evidence grading methodology. CONCLUSIONS: Rehabilitation needs more high-level studies. Some improvements in research methodology are relatively affordable (e.g., improved blinding), whereas others are expensive (e.g., large randomized controlled trials). Lower-level investigations reporting promising results need to be followed by more definitive, higher-level trials.

Brain Injuries↗
PubMed2006

Cognitive rehabilitation interventions for executive function: moving from bench to bedside in patients with traumatic brain injury.

Executive function mediated by prefrontally driven distributed networks is frequently impaired by traumatic brain injury (TBI) as a result of diffuse axonal injury and focal lesions. In addition to executive cognitive functions such as planning and working memory, the effects of TBI impact social cognition and motivation processes. To encourage application of cognitive neuroscience methods to studying recovery from TBI, associated reorganization of function, and development of interventions, this article reviews the pathophysiology of TBI, critiques currently employed methods of assessing executive function, and evaluates promising interventions that reflect advances in cognitive neuroscience. Brain imaging to identify neural mechanisms mediating executive dysfunction and response to interventions following TBI is also discussed.

Animals↗
PubMed2005

Predictors of outcome in prolonged posttraumatic disorders of consciousness and assessment of medication effects: A multicenter study.

OBJECTIVES: To develop predictive models of recovery from the vegetative state (VS) and minimally conscious state (MCS) after traumatic brain injury (TBI) and to gather preliminary evidence on the impact of various psychotropic medications on the recovery process to support future randomized controlled trials. Design Longitudinal observational cohort design, in which demographic information, injury and acute care history, neuroimaging data, and an initial Disability Rating Scale (DRS) score were collected at the time of study enrollment. Weekly follow-up data, consisting of DRS score, current psychoactive medications, and medical complications, were gathered until discharge from inpatient rehabilitation. SETTING: Seven acute inpatient rehabilitation facilities in the United States and Europe with specialized programs for treating patients in the VS and MCS. PARTICIPANTS: People with TBI (N=124) who were in the VS or MCS 4 to 16 weeks after injury. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: DRS score at 16 weeks after injury and time until commands were first followed (among those participants demonstrating no command following at study enrollment). Results DRS score at enrollment, time between injury and enrollment, and rate of DRS change during the first 2 weeks of poststudy observation were all highly predictive of both outcomes. No variables related to injury characteristics or lesions on neuroimaging were significant predictors. Of the psychoactive medications, amantadine hydrochloride was associated with greater recovery and dantrolene sodium was associated with less recovery, in terms of the DRS score at 16 weeks but not the time until commands were followed. More detailed analysis of the timing of functional improvement, with respect to the initiation of amantadine provided suggestive, but not definitive, evidence of the drug's causal role. CONCLUSIONS: These findings show the feasibility of improving outcome prediction from the VS and MCS using readily available clinical variables and provide suggestive evidence for the effects of amantadine and dantrolene, but these results require confirmation through randomized controlled trials.

Adult↗
PubMed2005

A patient registry for cognitive rehabilitation research: a strategy for balancing patients' privacy rights with researchers' need for access.

OBJECTIVE: To describe a consent-based Patient Research Registry designed to improve the quality and efficiency of cognitive rehabilitation research by balancing patients' privacy rights with researchers' need for access to research participants. DESIGN: Description of a protocol for a Patient Research Registry. SETTING: Three rehabilitation hospitals. PARTICIPANTS: Inpatients with stroke or traumatic brain injury (TBI) at the 3 participating hospitals. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Percentages of eligible patients with stroke or TBI who consented to be enrolled in the Registry, were subsequently contacted about a study, and ultimately participated in a study. A survey examined satisfaction with the Registry among researchers who used it for recruitment. RESULTS: After 36 months of operation, 58% of patients approached have consented to be in the Registry (N=1256). Eighty-seven percent of those later identified as potential subjects for research studies expressed interest, and 63% eventually participated. Researchers reported satisfaction with the recruitment opportunities afforded by the Registry. CONCLUSIONS: The Registry succeeded in identifying eligible patients interested in participating in research studies, while safeguarding their privacy rights. We identify its strengths and limitations and characterize the type of facility that would most profit from adopting this recruitment model.

Brain Injuries↗
PubMed2005

Executive function as a predictor of inattentive behavior after traumatic brain injury.

Emerging evidence from recent studies using laboratory and naturalistic attention tasks suggests that individuals with traumatic brain injury (TBI) may have a deficit mainly in strategic control of attention. In the present study, we tested the hypothesis that inattentive behavior after TBI could be predicted by performance on psychometric measures of executive function. A group of 37 individuals with moderate to severe TBI were assessed with previously validated naturalistic measures of attention. A battery of neuropsychological tests was also administered to assess various aspects of executive function. Seven measures of executive function and 10 variables reflecting inattentive behavior were combined to form 1 executive and 3 inattentive behavior (IB) composite scores. Three predictors (executive composite, current disability scores, and age) were associated, at the univariate level, with one of the IB composites reflecting frequency and duration of off-task episodes. A stepwise multiple regression procedure indicated that the executive composite was the only significant predictor of the IB composite. Additional post-hoc regression analyses suggested that the relationship was not likely to be mediated by processing speed. The current study supports the hypothesis that executive function, measured by commonly used neuropsychological tests, significantly predicts certain aspects of inattentive behavior in real-world tasks after TBI.

Adolescent↗
PubMed2004

Awareness of behavioral, cognitive, and physical deficits in acute traumatic brain injury.

OBJECTIVE: To compare awareness of deficit in 3 domains of function (physical, cognitive, behavioral/emotional) in acute traumatic brain injury (TBI), controlling for severity of impairment in the different domains. DESIGN: Inception cohort. SETTING: Three inpatient rehabilitation programs. PARTICIPANTS: People with acute TBI (N=161), tested as soon as feasible after posttraumatic amnesia. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Awareness Questionnaire (AQ) completed by the person with TBI and the treating neuropsychologist; and self- and clinician-rating scores calculated in the 3 domains. RESULTS: For participants who were rated by clinicians as more impaired in at least 1 domain (ie, scored lower on the AQ), self-ratings differed significantly from one another in all 3 domains, with behavioral self-ratings highest, physical self-ratings lowest, and cognitive self-ratings intermediate. In subgroups of participants rated at the same level by clinicians in all 3 domains, physical self-ratings were also lowest, that is, more consonant with clinician ratings. Participants tended to rate themselves as relatively unchanged in cognitive and behavioral domains regardless of the level of clinician ratings on these factors. CONCLUSIONS: Patterns of discrepant awareness of deficit in different functional areas seen in postacute TBI also appear to be present acutely and are not entirely related to differential severity of deficit. We discuss several possible reasons for discrepant awareness of deficit, including differences in internal and external feedback, cultural and psychologic factors, and different levels of ambiguity inherent in causal explanations for different types of problems.

Activities of Daily Living↗
PubMed2004

The JFK Coma Recovery Scale-Revised: measurement characteristics and diagnostic utility.

OBJECTIVE: To determine the measurement properties and diagnostic utility of the JFK Coma Recovery Scale-Revised (CRS-R). DESIGN: Analysis of interrater and test-retest reliability, internal consistency, concurrent validity, and diagnostic accuracy. SETTING: Acute inpatient brain injury rehabilitation hospital. PARTICIPANTS: Convenience sample of 80 patients with severe acquired brain injury admitted to an inpatient Coma Intervention Program with a diagnosis of either vegetative state (VS) or minimally conscious state (MCS). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The CRS-R, the JFK Coma Recovery Scale (CRS), and the Disability Rating Scale (DRS). RESULTS: Interrater and test-retest reliability were high for CRS-R total scores. Subscale analysis showed moderate to high interrater and test-retest agreement although systematic differences in scoring were noted on the visual and oromotor/verbal subscales. CRS-R total scores correlated significantly with total scores on the CRS and DRS indicating acceptable concurrent validity. The CRS-R was able to distinguish 10 patients in an MCS who were otherwise misclassified as in a VS by the DRS. CONCLUSIONS: The CRS-R can be administered reliably by trained examiners and repeated measurements yield stable estimates of patient status. CRS-R subscale scores demonstrated good agreement across raters and ratings but should be used cautiously because some scores were underrepresented in the current study. The CRS-R appears capable of differentiating patients in an MCS from those in a VS.

Adolescent↗
PubMed2004

Effect of methylphenidate on vital signs and adverse effects in adults with traumatic brain injury.

OBJECTIVE: To study methylphenidate's adverse effects and impact on vital signs within the adult traumatic brain injury population. DESIGN: Thirty-five adults with traumatic brain injury enrolled in a double-blind, placebo-controlled, 6-wk crossover study of methylphenidate, given in a dose of 0.3 mg/kg/dose, twice a day. Vital signs were taken by trained clinicians and research assistants. Participants filled out weekly questionnaires pertaining to the adverse effects. RESULTS: Poor appetite was the only adverse effect related to methylphenidate. Other adverse effects commonly associated with methylphenidate, such as insomnia, rapid heart rate, and anxiety, were not found to be significantly related to the medication. The average rise in mean arterial pressure on methylphenidate was 2.5 mm. Methylphenidate showed a stronger impact on pulse, with an average increase of 7 beats/min. Baseline vital signs did not predict the degree of increase on methylphenidate. CONCLUSION: Methylphenidate appears to be safe for the adult population with traumatic brain injury. However, because a few individuals experienced significant changes in vital signs and adverse effects, all patients should be monitored.

Adult↗
PubMed2004

Effects of methylphenidate on attention deficits after traumatic brain injury: a multidimensional, randomized, controlled trial.

OBJECTIVE: To evaluate the effects of methylphenidate on a variety of aspects of attention, ranging from laboratory-based impairment measures to caregiver ratings and work productivity, in individuals after traumatic brain injury. DESIGN: A total of 34 adults with moderate to severe traumatic brain injury and attention complaints in the postacute phase of recovery were enrolled in a 6-wk, double-blind, placebo-controlled, repeated crossover study of methylphenidate, administered in a dose of 0.3 mg/kg/dose, twice a day. A wide range of attentional measures was gathered weekly, including computerized and paper-and-pencil tests of attention, videotaped records of individual work in a distracting environment, real-time observational scoring of attentiveness in a classroom environment, and caregiver and clinician rating scales of attentiveness. Participants also attempted to guess their drug condition each week. Data from the first ten participants were used for pilot purposes, to develop attentional factors for composite scoring, and to identify attentional dimensions suggestive of a treatment effect for independent replication. The remaining 24 participants' results were used to confirm potential treatment effects seen in the pilot sample, using Wilcoxon's signed-ranks test on composite factor scores and individual variables. RESULTS: A total of 54 dependent variables were reduced to 13 composite factors and 13 remaining individual variables. Of the 13 attentional factors, five showed suggestive treatment effects in the pilot sample. Of these, three showed statistically significant treatment effects in the replication sample: speed of information processing (effect sizes, -0.06 to 0.48; P < 0.001), attentiveness during individual work tasks (effect sizes, 0.15-0.62; P = 0.01), and caregiver ratings of attention (effect sizes, 0.44-0.50; P = 0.01). Of the individual variables, four showed suggestive treatment effects in the pilot sample, but only one showed significant treatment effects in the replication sample: reaction time before errors in the Sustained Attention to Response Task (effect size, 0.20; P = 0.03). No treatment-related improvement was seen in divided attention, sustained attention, or susceptibility to distraction. None of the variables showed suggestive or definite negative treatment effects. Effect sizes for those performance measures positively affected by methylphenidate were in the small to medium range and included both impairment and activity level measures. Improvements in processing speed did not seem to come at the expense of accuracy. CONCLUSIONS: Methylphenidate, at 0.3 mg/kg/dose, given twice a day to individuals with attentional complaints after traumatic brain injury, seems to have clinically significant positive effects on speed of processing, caregiver ratings of attention, and some aspects of on-task behavior in naturalistic tasks. Further research is needed to identify the optimal dose and to extend these findings to less carefully selected individuals.

Adult↗
PubMed2004

Investigation of ethnic differences in willingness to enroll in a rehabilitation research registry: a study of the Northeast Cognitive Rehabilitation Research Network.

OBJECTIVE: To investigate differences between African American and white respondents in willingness to enroll in a rehabilitation research registry for future research and to determine if reasons for consenting and refusing to enroll differ by ethnicity. DESIGN: Inpatient recruitment results from 739 African American and white respondents in which patients were admitted to a rehabilitation hospital with a diagnosis of stroke or traumatic brain injury. RESULTS: A similar proportion of African American and white respondents (both patients and surrogates) consented to enroll in the registry (72% of all African American respondents vs. 68% of all white respondents). African Americans and whites provided similar reasons for consenting and refusing to enroll. Demographic variables associated with consent were: higher education, younger age, and facility. The odds of consenting to enroll in the registry were 5 times as high for those who thought they had a great deal to gain from enrollment compared with those who thought they had less to gain and were nearly 2 times as high for those who reported little concern about privacy compared with those who were more concerned about privacy. CONCLUSIONS: Ethnicity was not found to be a predictor of willingness to enroll in a study registry. A greater belief of gain and less concern over privacy were associated with willingness to enroll, even after controlling for age, education, facility, and ethnic group.

Adolescent↗