Mild Traumatic Brain Injury Group Research Articles

Heterogeneity of brain lesions in pediatric traumatic brain injury.

Magnetic resonance imaging (MRI) provides a method to identify and quantify abnormalities resulting from traumatic brain injury (TBI). MRI abnormalities in children with TBI have not been fully characterized according to the frequency, location, and quantitative measurement of a range of pathologies critical for studies of neuropsychological outcome. Here, we report MRI findings from a large, multicenter study of childhood TBI, the Social Outcomes of Brain Injury in Kids (SOBIK) study, which compared qualitative and quantitative neuroimaging findings in 72 children with complicated mild-to-severe TBI to 52 children with orthopedic injury (OI). Qualitative analyses of MRI scans coded white matter hyperintensities (WMHs), hemosiderin deposits reflecting prior hemorrhagic lesions, regions of encephalomalacia and/or atrophy, and corpus callosum atrophy and traumatic shear lesions. Two automated quantitative analyses were conducted: (a) FreeSurfer methods computed volumes for total brain, white matter (WM), gray matter (GM), corpus callosum, ventricles, amygdala, hippocampus, basal ganglia, and thalamus along with a ventricle-to-brain ratio (VBR); and (b) voxel-based morphometry (VBM) to identify WM, GM, and cerebrospinal fluid. We also examined performance on the Processing Speed Index (PSI) from the Wechsler Intelligence Scale for Children, Fourth Edition, in relation to the above-mentioned neuroimaging variables. WMHs, hemosiderin deposits, and focal areas of encephalomalacia or atrophy were common in children with TBI, were related to injury severity, and were mostly observed within a frontotemporal distribution. Quantitative analyses showed volumetric changes related to injury severity, especially ventricular enlargement and reduced corpus callosum volume. VBM demonstrated similar findings, but, in addition, GM reductions in the inferior frontal, basal forebrain region, especially in the severe TBI group. The complicated mild TBI group showed few differences from the OI group. PSI was significantly associated with global atrophy, as measured by VBR. MRI findings after childhood TBI are diverse and particularly influenced by injury severity, and they involve common features, group heterogeneity, and individual variability.

Poster 40 Comparing Patients With Mild Traumatic Brain Injury to Trauma Controls on CNS Vital Signs

To compare performance on a computerized neuropsychological test battery, CNS Vital Signs (CNS-VS), in a sample of patients with mild traumatic brain injury (MTBI) and trauma controls. Quasi-Experimental, Two-Group, Between-Subjects Design. Participants were 50 patients who met the WHO Collaborating Center Task Force criteria for MTBI and 31 trauma controls. Groups were similar in age, years of education, and estimated intellectual ability. A substantial minority (28%) of the MTBI group had a trauma-related abnormality on day-of-injury CT (i.e., a “complicated MTBI”). Participants were recruited from the Emergency Department of Vancouver General Hospital. The CNS-VS, which generates a Neurocognition Index (NCI) and five primary domain scores, was administered approximately six to eight weeks post injury. Differences in mean performance were examined with a MANOVA and exploratory ANOVAs. Differences in the frequency of low scores at four cutoffs (1SD, <10th percentile, ≤5th percentile, and there was no significant difference between groups for the NCI. A MANOVA using the five domain scores did not reveal statistically significant differences between the groups. Moreover, there were no group differences on any of the domain scores on exploratory ANOVAs. The frequencies of low scores at each cutoff, although more common in the MTBI sample, were not statistically different. At the group level, participants with MTBI did not differ on computerized testing when compared to trauma controls six to eight weeks following injury.

The Use of Magnetic Resonance Spectroscopy in the Subacute Evaluation of Athletes Recovering from Single and Multiple Mild Traumatic Brain Injury

Advanced neuroimaging techniques have shown promise in highlighting the subtle changes and nuances in mild traumatic brain injury (MTBI) even though clinical assessment has shown a return to pre-injury levels. Here we use ¹H-magnetic resonance spectroscopy (¹H-MRS) to evaluate the brain metabolites N-acetyl aspartate (NAA), choline (Cho), and creatine (Cr) in the corpus callosum in MTBI. Specifically, we looked at the NAA/Cho, NAA/Cr, and Cho/Cr ratios in the genu and splenium. We recruited 20 normal volunteers (NV) and 28 student athletes recovering from the subacute phase of MTBI. The MTBI group was categorized based upon the number of MTBIs and time from injury to ¹H-MRS evaluation. Significant reductions in NAA/Cho and NAA/Cr ratios were seen in the genu of the corpus callosum, but not in the splenium, for MTBI subjects, regardless of the number of MTBIs. MTBI subjects recovering from their first MTBI showed the greatest alteration in NAA/Cho and NAA/Cr ratios. Time since injury to ¹H-MRS acquisition was based upon symptom resolution and did not turn out to be a significant factor. We observed that as the number of MTBIs increased, so did the length of time for symptom resolution. Unexpected findings from this study are that MTBI subjects showed a trend of increasing NAA/Cho and NAA/Cr ratios that coincided with increasing number of MTBIs.

Predictive Value of Intracranial Flow Velocity for In-Hospital Mortality in Patients With Traumatic Brain Injury

To investigate the predictive value of intracranial blood flow velocity on in-hospital mortality in patients with traumatic brain injury (TBI), transcranial Doppler ultrasonography was performed in patients with mild (n=30), moderate (n=35), and severe (n=33) TBI. Bilateral middle cerebral artery was examined by transcranial Doppler ultrasonography and the time-averaged mean (Vm) velocities were used for analysis. Accelerated flow velocity (>65 cm/s) was detected in 57 (58.3%) patients. The proportion of patients with accelerated flow velocity in the moderate (62.9%) or severe TBI (69.7%) group was higher than in the mild TBI group (40%, P<0.01). Decelerated flow velocity (<35 cm/s) was detected in 11 (16.1%) patients. Five patients died during hospitalization. After adjusting age, the Glasgow Coma Scale score, and treatment measures (surgical or nonsurgical), a low flow velocity (<30 cm/s) was an independent predictor for in-hospital mortality (adjusted risk ratio, 3.6; 95% confidence interval, 1.32-11.62; P=0.01). We conclude that decelerated intracranial flow can be found in <20% of the patients with severe TBI, and a persistent flow velocity <30 cm/s is indicative of a poor clinical outcome such as in-hospital mortality.

Reliability, validity and clinical usefulness of the BNI fatigue scale in mild traumatic brain injury

Objectives: The purpose of this study was to examine the reliability, validity and clinical usefulness of the Barrow Neurological Institute Fatigue Scale (BNI-FS) in patients with mild traumatic brain injuries (MTBI).Methods and procedure: Participants were 125 patients enrolled from the Emergency Department (ED) of Tampere University Hospital, Finland who had sustained an MTBI. The average number of days from injury to the interview and questionnaires was 24.1 (SD = 5.4, Range = 8–38). The patients were compared to a healthy control sample. Patients completed the Barrow Neurological Institute Fatigue Scale, Fatigue Impact Scale (FIS), Beck Depression Inventory-Second Edition (BDI-II), Rivermead Post-concussion Symptom Questionnaire (RPSQ) and the health assessment measure EuroQol five Dimension (EQ-5D) Visual Analogue Scale (VAS).Results: The MTBI group had significantly greater total scores on the BNI-FS than the control group (p < 0.005, Cohen's d = 0.40). The internal consistency reliability for the BNI-FS, as measured by Cronbach's alpha, was 0.96 for the MTBI group and 0.87 for the control group. The 10 items were submitted to an exploratory principal components factor analysis with varimax rotation in the MTBI group. A one-factor solution, accounting for 73.3% of the total variance, appropriately summarized the data. The correlation between the BNI-FS and other measures was rs = 0.68 (p < 0.001) for the BDI-II, rs = 0.68 (p < 0.001) for the RPSQ, rs = −0.39 (p < 0.001) for the EQ-5D VAS and rs = 0.84 (p < 0.001) for the FIS. Fatigue ratings correlated positively with number of days post-injury before returning to work (rs = 0.27, p < 0.006).Conclusion: The BNI-FS is a relatively new, brief and highly reliable measure of fatigue.

Diffusion Tensor Imaging Findings Are Not Strongly Associated With Postconcussional Disorder 2 Months Following Mild Traumatic Brain Injury

To examine the relation between diffusion tensor imaging (DTI) of the corpus callosum and postconcussion symptom reporting following mild traumatic brain injury (MTBI). Sixty patients with MTBI and 34 patients with orthopedic/soft-tissue injuries (Trauma Controls) prospectively enrolled from consecutive admissions to a level 1 trauma center. Diffusion tensor imaging of the corpus callosum was undertaken using a Phillips 3T scanner at 6 to 8 weeks postinjury. Participants also completed a postconcussion symptom checklist. The MTBI group was divided into 2 subgroups based on the International Classification of Diseases, Tenth Revision symptom criteria for postconcussion disorder (PCD): PCD Present (n = 21), PCD Absent (n = 39). Measures of fractional anisotropy and mean diffusivity for the genu, body, and splenium of the corpus callosum. Participants also completed the British Columbia Post-Concussion Symptom Inventory. The MTBI group reported more postconcussion symptoms than the trauma controls. There were no significant differences between MTBI and trauma control groups on all DTI measures. In the MTBI sample, there were no significant differences on all DTI measures between those who did and did not meet the International Classification of Diseases, Tenth Revision research criteria for postconcussion disorder. These data do not support an association between white matter integrity in the corpus callosum and self-reported postconcussion syndrome 6 to 8 weeks post-MTBI.

An automatic MEG low-frequency source imaging approach for detecting injuries in mild and moderate TBI patients with blast and non-blast causes

Traumatic brain injury (TBI) is a leading cause of sustained impairment in military and civilian populations. However, mild (and some moderate) TBI can be difficult to diagnose because the injuries are often not detectable on conventional MRI or CT. Injured brain tissues in TBI patients generate abnormal low-frequency magnetic activity (ALFMA, peaked at 1-4 Hz) that can be measured and localized by magnetoencephalography (MEG). We developed a new automated MEG low-frequency source imaging method and applied this method in 45 mild TBI (23 from combat-related blasts, and 22 from non-blast causes) and 10 moderate TBI patients (non-blast causes). Seventeen of the patients with mild TBI from blasts had tertiary injuries resulting from the blast. The results show our method detected abnormalities at the rates of 87% for the mild TBI group (blast-induced plus non-blast causes) and 100% for the moderate group. Among the mild TBI patients, the rates of abnormalities were 96% and 77% for the blast and non-blast TBI groups, respectively. The spatial characteristics of abnormal slow-wave generation measured by Z scores in the mild blast TBI group significantly correlated with those in non-blast mild TBI group. Among 96 cortical regions, the likelihood of abnormal slow-wave generation was less in the mild TBI patients with blast than in the mild non-blast TBI patients, suggesting possible protective effects due to the military helmet and armor. Finally, the number of cortical regions that generated abnormal slow-waves correlated significantly with the total post-concussive symptom scores in TBI patients. This study provides a foundation for using MEG low-frequency source imaging to support the clinical diagnosis of TBI.

A Comparison of Long-Term Postconcussive Symptoms between University Students with and without a History of Mild Traumatic Brain Injury or Orthopedic Injury

Mild traumatic brain injury (mild TBI) is often associated with postconcussive symptoms such as headache, memory problems, and irritability. However, high rates of similar symptoms in groups without a history of TBI raise questions about the clinical validity of the postconcussive syndrome. This study was conducted to address these issues through systematic examination of symptoms reported by those with and without a history of mild TBI or orthopedic injury. Responses to the Postconcussion Syndrome Checklist (PCSC), demographic information, and medical history were collected via online questionnaire from 3027 non-referred university students (2280 without a history of mild TBI or orthopedic injury, 491 with a history of orthopedic injury, and 256 with post-acute mild TBI). Although the mild TBI group reported higher mean levels of symptoms, confirmatory factor analyses demonstrated that symptoms clustered into parallel cognitive, somatic, affective, and sensory factors in all three groups. Despite modestly higher mean symptoms among those with a history of mild TBI, symptom clusters did not differ from non-TBI groups. These findings cast doubts about the clinical validity of the "postconcussive syndrome" and raise questions about pathways by which mild TBI and other factors may influence the expression of chronic symptoms.

Voxel- and atlas-based analysis of diffusion tensor imaging may reveal focal axonal injuries in mild traumatic brain injury — comparison with diffuse axonal injury

BackgroundThe diagnosis and management of mild traumatic brain injury (MTBI) continue to be subjects of debate, with varying opinions regarding the extent to which tissue-based impairments versus the impacts of other stressors cause ongoing disability. Detecting areas of the brain with abnormalities that can explain symptoms and behavior in patients with MTBI is important in order to confirm the diagnosis of MTBI. MethodsIn this study, we calculated diffusion maps from results of diffusion tensor imaging (DTI) performed in an apparently healthy control group. We then compared these maps with those of patients with MTBI (MTBI group) or diffuse axonal injury (DAI group). All diffusion maps were normalized to the International Consortium for Brain Mapping atlas for atlas-based analysis and were segmented and normalized by the Diffeomorphic Anatomical Registration Through Exponentiated Lie tool in SPM8 to reduce misregistration. ResultsAll diffusion measures in the DAI group were lower than in the control group. There were significant differences in the body and splenium of the corpus callosum, fornix and right cerebral peduncle in the DAI group compared with the control group (P<.001). The MTBI group had higher axial diffusivity than the control group in the right corticospinal tract, left medial lemniscus, left inferior cerebellar peduncle, bilateral anterior limb of the internal capsule, right anterior corona radiata, bilateral cingulum (cingulate gyrus) and left superior frontooccipital fasciculus (P<.05). ConclusionsVoxel- and atlas-based analysis of DTI might suggest that patients with MTBI have focal axonal injury and that the pathophysiology is significantly different from that of DAI. These findings will help in the diagnosis of patients with MTBI.

Health Care Costs Associated with Traumatic Brain Injury and Psychiatric Illness in Adults

A cohort design was used to determine the contribution of traumatic brain injury (TBI) and psychiatric illness to health care costs for adolescents and adults in the 3 years following mild or moderate-to-severe TBI compared to a matched cohort without TBI, controlling for confounders. In all, 3756 subjects 15 years or older from a large health maintenance organization database were examined. We identified subjects who sustained a TBI in 1993 (n=939) and selected three control subjects per TBI-exposed subject (n=2817), matched for age, sex, and enrollment at the time of injury. Unadjusted mean costs in 2009-adjusted dollars were compared using Kruskal-Wallis tests and Mann-Whitney U tests, and adjusted mean costs were compared using gamma regression analyses. Average costs were 76% higher in the 3 years after injury for the mild TBI group, and 5.75 times greater for the moderate-to-severe TBI group compared to controls. The presence of psychiatric illness was associated with more than doubling of total costs for both inpatient and outpatient non-mental health care. Gamma regression analyses confirmed significantly higher costs in patients with TBI or psychiatric illness. A significant interaction between moderate-to-severe TBI and psychiatric illness indicated a 3.39 times greater cost among patients with both exposures compared with those exposed to moderate-to-severe TBI without psychiatric illness. TBI and psychiatric illness were each associated with significant increases in health care costs; those with the combination of moderate-to-severe TBI and psychiatric illness had much higher costs than any other group.

Outcome from Complicated versus Uncomplicated Mild Traumatic Brain Injury

Objective. To compare acute outcome following complicated versus uncomplicated mild traumatic brain injury (MTBI) using neurocognitive and self-report measures. Method. Participants were 47 patients who presented to the emergency department of Tampere University Hospital, Finland. All completed MRI scanning, self-report measures, and neurocognitive testing at 3-4 weeks after injury. Participants were classified into the complicated MTBI or uncomplicated MTBI group based on the presence/absence of intracranial abnormality on day-of-injury CT scan or 3-4 week MRI scan. Results. There was a large statistically significant difference in time to return to work between groups. The patients with uncomplicated MTBIs had a median of 6.0 days (IQR = 0.75–14.75, range = 0–77) off work compared to a median of 36 days (IQR = 13.5–53, range = 3–315) for the complicated group. There were no significant differences between groups for any of the neurocognitive or self-report measures. There were no differences in the proportion of patients who (a) met criteria for ICD-10 postconcussional disorder or (b) had multiple low scores on the neurocognitive measures. Conclusion. Patients with complicated MTBIs took considerably longer to return to work. They did not perform more poorly on neurocognitive measures or report more symptoms, at 3-4 weeks after injury compared to patients with uncomplicated MTBIs.

Impact of injury severity on transplantation of embryonic neural stem cells following traumatic brain injury in rats

Objective To explore the influence of injury severity on transplantation of embryonic neural stem cells (NSCs) after traumatic brain injury (TBI).Methods The NSCs were isolated from the hippocampus of fetal rats aged at from 12-14 days.The cells were cultured and proliferated in the serum-free medium and identified in vitro.The animals received transplants in the bilateral hippocampal areas at day 3 following mild or moderate TBI separately.Conventional histology,TUNEL and immunohistology were examined to detect BrdU,NSE,GFAP,GalC,NGF and BDNF at day 14 post-implantation.Results BrdU-labeled positive cells in the bilateral hippocampus in the mild TBI group were more than those in the moderate TBI group at day 14 post-implantation.Significant differentiation of the astrocytes recognized as GFAP positive cells in the bilateral hippocampus was found at day 14 post-implantation.The expression of NGF and BDNF proteins was increased following TBI,the most evident in the mild TBI group.Conclusion The influence of injury severity on transplantation may be associated with the change of the microenvironment after TBI. Key words: Brain injuries; Stem cells; Embryo; Rats

Comparison of subjective cognitive complaints with neuropsychological tests in individuals with mild vs more severe traumatic brain injuries

Primary objective: The aim of this study was to examine the complex inter-relationship between subjective reports of cognitive impairments and neuropsychological performances in compensation-seeking individuals with traumatic brain injury (TBI) of differing severities. Specifically, this study examined: (a) the participants’ neuropsychological test scores and self-reported ratings according to TBI severity; (b) whether there was a predictive relationship between self-report and cognitive test scores; and (c) the influence of emotional functioning on self-reported cognitive functioning.Research design: A multi-group comparative research design was employed.Methods and procedure: An outpatient sample of 61 patients with TBIs using neuropsychological testing, RNBI (Ruff Neurobehavioral Inventory) and clinical interviews.Main outcomes and results: The mild TBI group exhibited greater attentional impairments, while the moderate-to-severe group exhibited greater memory and learning impairments on neuropsychological tests. The mild group reported more cognitive symptoms than their more severely damaged counterparts. The mild TBI participants reported significantly more symptoms of post-traumatic stress disorder (PTSD).Conclusions: Individuals with moderate-to-severe TBI were more accurate when reporting their memory and learning difficulties, whereas individuals with mild TBI were more accurate when reporting attentional difficulties. It is likely that the occurrence of PTSD worsens the outcome of a mild TBI. There likely is a cumulative effect between the PTSD symptoms and the emotional residuals in the mild TBI population.

Differential response patterns on the Personality Assessment Inventory (PAI) in compensation-seeking and non-compensation-seeking mild traumatic brain injury patients

There is relatively little research on the Personality Assessment Inventory (PAI) with mild traumatic brain injury (MTBI) populations. There is also little research on how compensation-seeking status affects personality assessment results in MTBI patients. The current study examined the PAI scales and subscales in two MTBI groups, one composed of compensation-seeking MTBI patients and the other consisting of non-compensation-seeking MTBI patients. Results indicated significant differences on several scales and subscales between the two MTBI groups, with the compensation-seeking MTBI patients having significantly higher elevations on scales related to somatic preoccupation (Somatic Complaint Scale, SOM), emotional distress (Anxiety Scale, ANX; Anxiety Related Disorders Scale, ARD; Depression Scale, DEP), and the Negative Impression Management, NIM, validity scale. All the SOM subscales and the Anxiety Cognitive (ANX-C) and ANX Affective, ANX-A, subscales were also elevated in the compensation-seeking group. Results indicated that several scales on the PAI were sensitive to group differences in compensation-seeking status in MTBI patients.

Slowing Down after a Mild Traumatic Brain Injury: A Strategy to Improve Cognitive Task Performance?

Long-term persistent attention and memory difficulties following a mild traumatic brain injury (TBI) often go undetected on standard neuropsychological tests, despite complaints by mild TBI individuals. We conducted a visual Repetition Detection working memory task to digits, in which we manipulated task difficulty by increasing cognitive load, to identify subtle deficits long after a mild TBI. Twenty-six undergraduate students with a self-report of one mild TBI, which occurred at least 6 months prior, and 31 non-head-injured controls took part in the study. Participants were not informed until study completion that the study's purpose was to examine cognitive changes following a mild TBI, to reduce the influence of "diagnosis threat" on performance. Neuropsychological tasks did not differentiate the groups, though mild TBI participants reported higher state anxiety levels. On our working memory task, the mild TBI group took significantly longer to accurately detect repeated targets on our task, suggesting that slowed information processing is a long-term consequence of mild TBI. Accuracy was comparable in the low-load condition and, unexpectedly, mild TBI performance surpassed that of controls in the high-load condition. Temporal analysis of target identification suggested a strategy difference between groups: mild TBI participants made a significantly greater number of accurate responses following the target's offset, and significantly fewer erroneous distracter responses prior to target onset, compared with controls. Results suggest that long after a mild TBI, high-functioning young adults invoke a strategy of delaying their identification of targets in order to maintain, and facilitate, accuracy on cognitively demanding tasks.

Quality of Life in Pediatric Mild Traumatic Brain Injury and its Relationship to Postconcussive Symptoms

Mild traumatic brain injury (TBI) and injury-related outcomes such as postconcussive symptoms (PCS) may influence health-related quality of life (HRQOL) in children. We evaluated HRQOL in 186 8- to 15-year-old children with mild TBI and 99 children with orthopedic injuries (OI). Parents rated the frequency and severity of PCS at an initial assessment within 2-weeks postinjury and rated HRQOL at 3- and 12-months postinjury. The mild TBI and OI groups did not differ in psychosocial HRQOL, but the mild TBI group showed lower physical HRQOL at the 12-month follow-up. Somatic PCS were a significant predictor of physical HRQOL over time, and both cognitive and somatic PCS were significant predictors of psychosocial HRQOL over time. Children with higher PCS at the initial assessment had lower HRQOL scores at later time points. Effective management of PCS may be associated with improvements in HRQOL following pediatric mild TBI.

Do Postconcussive Symptoms Discriminate Injury Severity in Pediatric Mild Traumatic Brain Injury?

To assess whether postconcussive symptoms (PCS) can be used to discriminate injury severity among children with mild traumatic brain injury (TBI). One hundred eighty-six children with mild TBI, divided into high and low injury severity depending on whether the injury was associated with a loss of consciousness (LOC), and a comparison group of 99 children with orthopedic injuries (OI), all aged 8 to 15 years at the time of injury. Parent-rated frequency and severity of PCS at initial assessment within 2 weeks postinjury and again at 3 and 12 months postinjury. Ratings of PCS obtained at the initial and 3-month assessments differentiated children with mild TBI from OI, although only ratings at the initial assessment discriminated among all 3 groups. Somatic PCS accounted for most of the discriminatory power. Overall, the accuracy of group classification was relatively modest, with a large proportion of misclassifications of children in the mild-TBI groups. Although children with mild TBI have more PCS than children with OI, PCS do not permit sufficiently accurate discrimination of mild TBI and injury severity to warrant diagnostic decisions at this time.

The incidence of traumatic brain injury in young people in the catchment area of the University Hospital Rotterdam, The Netherlands

Background Traumatic brain injury (TBI) is in the developed countries the most common cause of death and disability in childhood. Aim The purpose of this study is to estimate the incidence of TBI for children and young people in an urbanised region of the Netherlands and to describe relevant characteristics of this group. Methods Patients, aged 1 month - 24 years who presented with traumatic brain injury at the Erasmus University Hospital (including the Sophia Children’s Hospital) in 2007 and 2008 were included in a retrospective study. Data were collected by means of diagnosis codes and search terms for TBI in patient records. The incidence of TBI in the different referral areas of the hospital for standard, specialised and intensive patient care was estimated. Results 472 patients met the inclusion criteria. The severity of the Injury was classified as mild in 342 patients, moderate in 50 patients and severe in 80 patients. The total incidence of traumatic brain injury in the referral area of the Erasmus University Hospital was estimated at 113.9 young people per 100.000. The incidence for mild traumatic brain injury was estimated at 104.4 young people, for moderate 6.1 and for severe 3.4 young people per 100.000. Conclusion The ratio for mild, moderate and severe traumatic brain injury in children and young people was 33.7–1.8–1.In the mild TBI group almost 17% of the patients reported sequelae. The finding that 42% of them had a normal brain CT scan at admission underwrites the necessity of careful follow up of children and young people with mild TBI.

Dopaminergic Challenge With Bromocriptine One Month After Mild Traumatic Brain Injury: Altered Working Memory and BOLD Response

Catecholamines, particularly dopamine, modulate working memory (WM). Altered sensitivity to dopamine might play a role in WM changes observed after traumatic brain injury (TBI). Thirty-one healthy controls (HC) and 26 individuals with mild TBI (MTBI) 1 month after injury were challenged with bromocriptine versus placebo before administration of a verbal WM functional MRI task. Bromocriptine was associated with improved WM performance in the HC but not the MTBI group. On bromocriptine, the MTBI group showed increased activation outside of a task-specific region of interest. Findings are consistent with the hypothesis that individuals with MTBI have altered responsivity to dopamine.

Alpha-2 adrenergic challenge with guanfacine one month after mild traumatic brain injury: Altered working memory and BOLD response

Alterations in working memory (WM) are common after traumatic brain injury (TBI). Frontal catecholaminergic systems, including the alpha-2 adrenergic system, modulate WM function and may be affected in TBI. We hypothesized that administration of an alpha-2 adrenergic agonist might improve WM after mild TBI (MTBI). Thirteen individuals with MTBI 1 month after injury and 14 healthy controls (HC) were challenged with guanfacine and placebo prior to administration of a verbal WM functional MRI task. Guanfacine was associated with improved WM performance in the MTBI but not the HC group. On guanfacine the MTBI group showed increased activation within a WM task-specific region of interest. Findings are consistent with the hypothesis that alterations in WM after MTBI may be improved with the alpha-2 agonist guanfacine.