Successful outcome in severe traumatic brain injury: a case study.

This case study describes the management of a 54-year-old male who presented to the Hospital of the University of Pennsylvania (HUP) with a traumatic brain injury (TBI) after being assaulted. He underwent an emergent bifrontal decompressive hemicraniectomy for multiple, severe frontal contusions. His postoperative course included monitoring of intracranial pressure, cerebral perfusion pressure, partial pressure of brain oxygen, brain temperature, and medical management based on HUP's established TBI algorithm. This case study explores the potential benefit of combining multimodality monitoring and TBI guidelines in the management of severe TBI.     

Arrested development and disrupted callosal microstructure following pediatric traumatic brain injury: relation to neurobehavioral outcomes

Chronic pediatric traumatic brain injury (TBI) is associated with significant and persistent neurobehavioral deficits. Using diffusion tensor imaging (DTI), we examined area, fractional anisotropy (FA), radial diffusion, and axial diffusion from six regions of the corpus callosum (CC) in 41 children and adolescents with TBI and 31 comparison children. Midsagittal cross-sectional area of the posterior body and isthmus was similar in younger children irrespective of injury status; however, increased area was evident in the older comparison children but was obviated in older children with TBI, suggesting arrested development. Similarly, age was correlated significantly with indices of tissue microstructure only for the comparison group. TBI was associated with significant reduction in FA and increased radial diffusivity in the posterior third of the CC and in the genu. The axial diffusivity did not differ by either age or group. Logistic regression analyses revealed that FA and radial diffusivity were equally sensitive to post-traumatic changes in 4 of 6 callosal regions; radial diffusivity was more sensitive for the rostral midbody and splenium. IQ, working memory, motor, and academic skills were correlated significantly with radial diffusion and/or FA from the isthmus and splenium only in the TBI group. Reduced size and microstructural changes in posterior callosal regions after TBI suggest arrested development, decreased organization, and disrupted myelination. Increased radial diffusivity was the most sensitive DTI-based surrogate marker of the extent of neuronal damage following TBI; FA was most strongly correlated with neuropsychological outcomes.     

Employment outcome four years after a severe traumatic brain injury: results of the Paris severe traumatic brain injury study

Objective: To describe employment outcome four years after a severe traumatic brain injury by the assessment of individual patients’ preinjury sociodemographic data, injury-related and postinjury factors.

Design: A prospective, multicenter inception cohort of 133 adult patients in the Paris area (France) who had received a severe traumatic brain injury were followed up postinjury at one and four years. Sociodemographic data, factors related to injury severity and one-year functional and cognitive outcomes were prospectively collected.

Methods: The main outcome measure was employment status. Potential predictors of employment status were assessed by univariate and multivariate analysis.

Results: At the four-year follow-up, 38% of patients were in paid employment. The following factors were independent predictors of unemployment: being unemployed or studying before traumatic brain injury, traumatic brain injury severity (i.e., a lower Glasgow Coma Scale score upon admission and a longer stay in intensive care) and a lower one-year Glasgow Outcome Scale–Extended score.

Conclusion: This study confirmed the low rate of long-term employment amongst patients after a severe traumatic brain injury. The results illustrated the multiple determinants of employment outcome and suggested that students who had received a traumatic brain injury were particularly likely to be unemployed, thus we propose that they may require specific support to help them find work.

• Implications for rehabilitation

• Traumatic brain injury is a leading cause of persistent disablity and can associate cognitive, emotional, physical and sensory impairments, which often result in quality-of-life reduction and job loss.

• Predictors of post-traumatic brain injury unemployment and job loss remains unclear in the particular population of severe traumatic brain injury patients.

• The present study highlights the post-traumatic brain injury student population require a close follow-up and vocational rehabilitation.

• The study suggests that return to work post-severe traumatic brain injury is frequently unstable and workers often experience difficulties that caregivers have to consider.

     

Survival and functional outcome in pediatric traumatic brain injury: a retrospective review and analysis of predictive factors

OBJECTIVE: The aim of this study was to evaluate the relationship of patient care variables to survival and functional outcome in the pediatric population with traumatic brain injury. DESIGN: Retrospective chart review. SETTING: A 16-bed pediatric critical care unit in an academic community children's hospital. PATIENTS: A total of 320 consecutive pediatric patients with traumatic brain injuries admitted to our pediatric critical care unit between 1992 and 1996. INTERVENTIONS: Patients were managed using our standard traumatic brain injury protocol. MEASUREMENTS AND MAIN RESULTS: A total of 230 patient variables encompassing demographic data, prehospital, emergency department, and pediatric critical care unit care were recorded. A total of 79 patients were severely injured, with admitting Glasgow Coma Scale scores of < or =10. There were 18 deaths. Only two patients survived without cognition. Ninety-five of 302 survivors required inpatient rehabilitation. Of these, 73 were old enough to be compared using FIMTM scores. At the time of discharge from rehabilitation, 52 patients (71%) were functioning independently, 20 (27%) were moderately dependent, and one patient was completely dependent. Analysis of variables with respect to survival revealed that an inability to maintain a cerebral perfusion pressure of > or =50 mm Hg on the first pediatric critical care unit day (p =.0002) and the presence of bradycardia in the emergency department (p =.0139) were the strongest factors associated with mortality. By using the regression equation generated from this model, we could correctly identify survivors and nonsurvivors with a predictive value of 94%. CONCLUSIONS: The ability to maintain a cerebral perfusion pressure of > or =50 mm Hg was the single most important predictor of traumatic brain injury survival in this study. This suggests that monitoring and optimizing cerebral perfusion pressure is critical to the management of these patients. The relationship between cognitive outcome and therapeutic interventions used to optimize cerebral perfusion pressure is unclear and requires further evaluation in a large prospective study.     

Amantadine in pediatric patients with traumatic brain injury: a retrospective, case-controlled study

OBJECTIVE: To determine if amantadine use in pediatric patients with traumatic brain injury is well tolerated and to attempt to assess its effectiveness. DESIGN: This was a retrospective, case-controlled study. RESULTS: Of the 54 patients, aged 3-18 yrs, who were administered amantadine, five (9%) had side effects that might have been related to the drug. These included hallucinations, delusions, increased aggression, and nausea/vomiting. The side effects were reversed when the medication was stopped or the dosage decreased. Patients in the amantadine group had a greater increase in Ranchos Los Amigos level during their admission than those in the control group (median, 3 vs. 2; P < 0.01). This difference may be, at least in part, explained by the fact that the amantadine group started at a lower Ranchos Los Amigos level (median, 3 vs. 4; P < 0.01). There were subjective improvements noted in 29 of the 46 patients (63%) in the amantadine group whose full charts were available for review. CONCLUSION: Amantadine is a well tolerated medication when it is used in pediatric patients with traumatic brain injury. Subjective improvements were noted in the majority of the patients administered amantadine, and the amantadine group showed a greater improvement in Ranchos Los Amigos level during admission, suggesting that it may be effective.     

Severity and correlates of brain fog in people with traumatic brain injury

Brain fog is one symptom that has been underexplored in traumatic brain injury (TBI). We explored the cognitive and affective correlates of brain fog in people with symptomatic mild TBI (n = 15), moderate-to-severe TBI (n = 15), and a healthy control group (n = 16). Measures across the studies assessed “brain fog” (Mental Clutter Scale), objective cognition (Useful Field of View® and Cogstate Brief Battery®), post-concussive symptoms (Post-Concussion Symptom Scale), and depressive symptoms (Profile of Moods Scale). Brain fog was higher in symptomatic mild TBI and moderate-to-severe TBI compared with healthy controls. Greater brain fog corresponded to greater depressive symptoms in symptomatic mild TBI. Greater brain fog corresponded to poorer episodic memory and working memory in moderate-to-severe TBI. Brain fog appears to reflect challenges in recovery, including depressive symptoms and worse cognitive function. Screening for brain fog might be worthwhile in people with brain injuries.     

Intensive care for pediatric traumatic brain injury

Purposes

The aims of this study are to describe a cohort of head-injured pediatric patients, focusing on current practice for intracranial pressure (ICP) monitoring and treatment and to verify the relationship between clinical and radiological parameters and the six-month outcome in a multivariable statistical model.

Methods

A retrospective review was done of a prospectively collected database considering patients younger than 19?years admitted to three neuro-intensive care units (ICU). Patients were divided into four age groups: 0?C5 (infant), 6?C12 (children), 13?C16 (pre-adolescent) and 17?C18?years (adolescent). The ICP and cerebral perfusion pressure (CPP) were analyzed calculating average data and values exceeding thresholds for more than 5?min. Outcome was assessed 6?months after trauma using the Glasgow Outcome Score.

Results

There were 199 patients, 155 male, included. Sixty percent had extracranial injuries. Pupils were abnormal in 38?%. Emergency evacuation of intracranial hematomas was necessary in 81 cases. The ICP was monitored in 117 patients; in 87 cases ICP was higher than 20?mmHg, with no differences among age groups. All but six patients received therapy to prevent raised ICP; barbiturates, deep hyperventilation or surgical decompression were used in 31 cases. At 6?months, mortality was 21?% and favorable outcome was achieved by 72?%. Significant predictors of outcome in the multivariable model were the Glasgow Coma Scale (GCS) motor score, pupils and ICP.

Conclusions

Pediatric head injury is associated with a high incidence of intracranial hypertension. Early surgical treatment and intensive care may achieve favorable outcome in the majority of cases.     

Influence of definition and location of hypotension on outcome following severe pediatric traumatic brain injury

OBJECTIVE: To examine the influence of definition and location (field, emergency department, or pediatric intensive care unit) of hypotension on outcome following severe pediatric traumatic brain injury. DESIGN: Retrospective cohort study. SETTING: Harborview Medical Center (level I pediatric trauma center), Seattle, WA, over a 5-yr period between 1998 and 2003. PATIENTS: Ninety-three children <14 yrs of age with traumatic brain injury following injury, head Abbreviated Injury Score > or = 3, and pediatric intensive care unit admission Glasgow Coma Scale score <9 formed the analytic sample. Data sources included the Harborview Trauma Registry and hospital records. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The relationship between hypotension and outcome was examined comparing two definitions of hypotension: a) systolic blood pressure <5th percentile for age; and b) systolic blood pressure <90 mm Hg. Hospital discharge Glasgow Outcome Score <4 or disposition of either death or discharge to a skilled nursing facility was considered a poor outcome. Pediatric intensive care unit and hospital length of stay were also examined. Systolic blood pressure <5th percentile for age was more highly associated with poor hospital discharge Glasgow Outcome Score (p = .001), poor disposition (p = .02), pediatric intensive care unit length of stay (rate ratio 9.5; 95% confidence interval 6.7-12.3), and hospital length of stay (rate ratio 18.8; 95% confidence interval 14.0-23.5) than systolic blood pressure <90 mm Hg. Hypotension occurring in either the field or emergency department, but not in the pediatric intensive care unit, was associated with poor Glasgow Outcome Score (p = .008), poor disposition (p = .03), and hospital length of stay (rate ratio 18.7; 95% confidence interval 13.1-24.2). CONCLUSIONS: Early hypotension, defined as systolic blood pressure <5th percentile for age in the field and/or emergency department, was a better predictor of poor outcome than delayed hypotension or the use of systolic blood pressure <90 mm Hg.     

Cognitive outcome in traumatic brain injury survivors

PURPOSE OF REVIEW: This review discusses recent studies investigating the cognitive and psychiatric outcome of posttraumatic brain injury. In addition, it aims to highlight key areas for future research. RECENT FINDINGS: Detailed cognitive assessments have revealed particular deficits in processing speed in the visual domain and the detrimental impact of interference on attentional performance. A pilot functional imaging study revealed neural changes in survivors performing a response inhibition task, even when matched to controls on behavioural indices. Recent psychiatric studies highlight the incidence of these disorders in the survivors and attempt to characterize distinct psychiatric profiles. Adult and child survivors appear to show differential difficulties. Successful rehabilitation strategies addressing these psychiatric and cognitive deficits include holistic intensive neuropsychological interventions and the introduction of electronic devices. Systematic randomized trials are needed to provide an adequate evidence base for clinical practice. The potential for cognitive enhancement using psychopharmacological agents has yet to be exploited. These treatments may lead to improved quality of life for traumatic brain injury survivors and their families. SUMMARY: Survivors of head injury show a diverse pattern of cognitive and psychiatric profiles. Recent research highlights the nature of some of these deficits and possible ways to enhance functioning. However, the area is well poised for rapid progress in the understanding of cognitive and emotional dysfunction following traumatic brain injury (TBI) and its rehabilitation through neuropsychological and psychopharmacological means.     

Hyperoxemia and long-term outcome after traumatic brain injury

Introduction

The relationship between hyperoxemia and outcome in patients with traumatic brain injury (TBI) is controversial. We sought to investigate the independent relationship between hyperoxemia and long-term mortality in patients with moderate-to-severe traumatic brain injury.

Methods

The Finnish Intensive Care Consortium database was screened for mechanically ventilated patients with a moderate-to-severe TBI. Patients were categorized, according to the highest measured alveolar-arterial O₂ gradient or the lowest measured PaO₂ value during the first 24 hours of ICU admission, to hypoxemia (<10.0 kPa), normoxemia (10.0 to 13.3 kPa) and hyperoxemia (>13.3 kPa). We adjusted for markers of illness severity to evaluate the independent relationship between hyperoxemia and 6-month mortality.

Results

A total of 1,116 patients were included in the study, of which 16% (n = 174) were hypoxemic, 51% (n = 567) normoxemic and 33% (n = 375) hyperoxemic. The total 6-month mortality was 39% (n = 435). A significant association between hyperoxemia and a decreased risk of mortality was found in univariate analysis (P = 0.012). However, after adjusting for markers of illness severity in a multivariate logistic regression model hyperoxemia showed no independent relationship with 6-month mortality (hyperoxemia vs. normoxemia OR 0.88, 95% CI 0. 63 to 1.22, P = 0.43; hyperoxemia vs. hypoxemia OR 0.97, 95% CI 0.63 to 1.50, P = 0.90).

Conclusion

Hyperoxemia in the first 24 hours of ICU admission after a moderate-to-severe TBI is not predictive of 6-month mortality.     

Using early neuropsychologic testing to predict long-term productivity outcome from traumatic brain injury

OBJECTIVE: To evaluate whether early neuropsychologic testing is useful in predicting long-term productivity outcome after traumatic brain injury (TBI). DESIGN: Validation cohort prediction study. SETTING: Four inpatient brain injury rehabilitation programs participating in the Traumatic Brain Injury Model Systems project. PARTICIPANTS: A total of 293 adults with nonpenetrating TBI. MAIN OUTCOME MEASURES: Fifteen neuropsychologic tests were administered to patients who emerged from posttraumatic amnesia before rehabilitation discharge. Test scores were classified in the normal range or impaired range, using objective criteria. Outcome was defined as productive if the patient was competitively employed or enrolled full time in regular education. RESULTS: Productivity at follow-up was predicted by completion of at least 1 neuropsychologic test before discharge, by an injury-test interval of less than 2 months, and by normal range scores on 10 of the 15 neuropsychologic tests. Normal range scores on these tests increased the probability of a productive outcome by 40% to 130%. CONCLUSIONS: Neuropsychologic testing can help predict long-term productivity even when performed before discharge from inpatient rehabilitation and at variable injury-test intervals. Early testing should be interpreted in relation to injury-test interval. Because tests of multiple neuropsychologic domains predicted outcome, comprehensive evaluations might be more useful in predicting outcome.     

Predictors of driving outcome after traumatic brain injury

OBJECTIVE: To examine predictors of driving status and fitness to drive after traumatic brain injury (TBI). DESIGN: Retrospective and prospective follow-up of a cohort ranging from 4 months to 10 years post-TBI. SETTING: A Midwestern, urban university-affiliated rehabilitation hospital. PARTICIPANTS: Seventy-one pairs of adults who had sustained a TBI and their significant others. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Driving status (whether the patient resumed driving), driving frequency (estimated miles driven per week), and postinjury driving records compiled by the Department of Motor Vehicles. RESULTS: Logistic and hierarchical regression analyses indicated that the significant other's perceptions of the patient's fitness to drive were the strongest predictor of patients' driving status and driving frequency. However, years postinjury, disability at discharge, and current neuropsychologic functioning best predicted postinjury driving safety as measured by actual incidents. The relation between perception of patients' fitness and actual driving incidents, however, was modest. CONCLUSIONS: Neuropsychologic and medical information available by traditional methods showed unique value in predictive driving safety. However, caregiver perception of patients' fitness was the overwhelming determinant of whether and how much patients drive. The bases on which caregivers form their opinions affect the safety of patients and the public. The rehabilitation setting is a unique resource for family education regarding abilities essential to safe driving.     

Post-concussion symptoms after mild traumatic brain injury: influence of demographic factors and injury severity in a 1-year cohort study

Purpose. To assess the prevalence and variation of post-concussion symptoms within the first year after mild traumatic brain injury (TBI), and explore the association between injury severity, demographic factors and symptoms.

Methods. Prospective study of patients with mild TBI followed up at 3, 6 and 12 months (N = 96 included, n = 52 attending all follow-ups). Sociodemographic factors, injury mechanisms and impact of injury (Glasgow Coma Scale score, Abbreviated Injury Severity Score (AIS), Injury Severity Score) were recorded at inclusion. Symptoms were reported in the Rivermead Post-Concussion Symptoms Questionnaire (RPQ) at the follow-ups. The sumscore of all symptoms in RPQ was calculated for each subject. Scores were also calculated separately for the cognitive, physical and behavioural symptoms.

Results. Twenty-nine subjects met the post-concussion syndrome criteria at 3 months, and 22 patients at 6 and 12 months. The cognitive symptoms were more prominent than the physical and behavioural symptoms. The cognitive and physical symptoms were associated with AIS for the head injury at 3 months, but not at 12 months. Considerable individual variability in the symptom pattern was found, and the subjects who attended only the 3-months follow-up reported a lower level of symptoms than those attending all follow-ups.

Conclusions. Persistence of symptoms was a considerable problem even 1 year after the injury, with cognitive symptoms dominating. More severe AIS scores were associated with a higher level of cognitive and physical symptoms at 3 months, but not at later follow-ups. Strategies to prevent and treat these symptoms should be focussed in clinical practice.     

Modelling 5-year functional outcome in a major traumatic injury survivor cohort

Aim. To estimate associations between possible predictors of functional disability outcome at 5 years in a working adult population cohort of survivors of major traumatic injury and to develop a prognostic model of outcome.

Design. Population based retrospective cohort study.

Population. Persons who had experienced major traumatic injury (Injury Seventy Score >15) in the area of the former Yorkshire Regional Health Authority during the period 30 September 1988 to 1 October 1989 and who survived for 5 years (average 5.3 years).

Methods. The same interviewer saw each survivor at their home and used the OPCS Adult Disability Schedule to ascertain levels of functional disability. Disability scores for each survivor were then combined in accordance with the OPCS guidance to calculate a level of disability between 0 (no disability) to 10 (maximum disability). The OPCS level was then dichotomised with a cut-point at 4/5. Possible predictor and confounding variables from pre-injury, injury and post-injury periods were modelled in a logistic regression to identify those that predicted outcome level. Two reduced models were developed to allow early prognosis of late outcome.

Results. The full model correctly classified 91% of observed outcomes. Inpatient length of stay OR 1.031 (95% CI 1.014,1.048) per day predicted poorer 5-year outcome; Glasgow Coma Score OR 0.790(0.629,0.992) per 1 point increase; stay in Intensive Care Unit OR 0.931 (0.877,0.987) per day; attainment of degree-level education OR 0.014 (0.000,0.707); single civil status OR 0.110 (0.013,0.908); being taken initially to a hospital with a neurosurgical facility OR 0.064(0.010,0.420); being in paid work during the 2 weeks before index injury OR 0.093(0.009,0.969) predicted better 5-year disability outcome. Two reduced models were constructed that included a simple set of variables, one of these models excluded any rehabilitation variables but still correctly classified 85% of the observed outcomes.

Conclusion. As well as level of traumatic brain injury (TBI) and total inpatient stay, Pre-injury educational attainment and employment, civil status, immediate care in a hospital with a neurosurgical facility and stay in an Intensive Care Unit determined 5-year outcome. It is possible to efficiently predict outcome at an early stage. Previous work on predictors of disablement have suffered from large selection and attrition biases.     

Indicators of long-term return to work after severe traumatic brain injury: A cohort study

Background

Return to work (RTW) is a major objective in the rehabilitation of individuals with severe traumatic brain injury (TBI). Implications for long-term occupational integration (beyond 5 years) have rarely been studied.

Modelling 5-year functional outcome in a major traumatic injury survivor cohort

AIM: To estimate associations between possible predictors of functional disability outcome at 5 years in a working adult population cohort of survivors of major traumatic injury and to develop a prognostic model of outcome. DESIGN: Population based retrospective cohort study. POPULATION: Persons who had experienced major traumatic injury (Injury Seventy Score >15) in the area of the former Yorkshire Regional Health Authority during the period 30 September 1988 to 1 October 1989 and who survived for 5 years (average 5.3 years). METHODS: The same interviewer saw each survivor at their home and used the OPCS Adult Disability Schedule to ascertain levels of functional disability. Disability scores for each survivor were then combined in accordance with the OPCS guidance to calculate a level of disability between 0 (no disability) to 10 (maximum disability). The OPCS level was then dichotomised with a cut-point at 4/5. Possible predictor and confounding variables from pre-injury, injury and post-injury periods were modelled in a logistic regression to identify those that predicted outcome level. Two reduced models were developed to allow early prognosis of late outcome. RESULTS: The full model correctly classified 91% of observed outcomes. Inpatient length of stay OR 1.031 (95% CI 1.014,1.048) per day predicted poorer 5-year outcome; Glasgow Coma Score OR 0.790(0.629,0.992) per 1 point increase; stay in Intensive Care Unit OR 0.931 (0.877,0.987) per day; attainment of degree-level education OR 0.014 (0.000,0.707); single civil status OR 0.110 (0.013,0.908); being taken initially to a hospital with a neurosurgical facility OR 0.064(0.010,0.420); being in paid work during the 2 weeks before index injury OR 0.093(0.009,0.969) predicted better 5-year disability outcome. Two reduced models were constructed that included a simple set of variables, one of these models excluded any rehabilitation variables but still correctly classified 85% of the observed outcomes. CONCLUSION: As well as level of traumatic brain injury (TBI) and total inpatient stay, Pre-injury educational attainment and employment, civil status, immediate care in a hospital with a neurosurgical facility and stay in an Intensive Care Unit determined 5-year outcome. It is possible to efficiently predict outcome at an early stage. Previous work on predictors of disablement have suffered from large selection and attrition biases.     

Functional outcome following traumatic brain injury: the Turkish experience

The objectives of this study were to describe the demographic characteristics and the nature of the functional recovery in a group of Turkish survivors of traumatic brain injury (TBI) who were referred for inpatient rehabilitation and identify variables correlated with discharge functional status as measured by the Functional Independence Measure (FIM). There were 40 patients in the study, 32 (69.6%) male and eight (17.4%) female, mean age 28+/-9.8 years. Motor vehicle accidents accounted for 62.5% of injuries, 22.5% of injuries occurred from violence and 15% resulted from falls. The mean durations of acute hospital stay, coma, and rehabilitation stay was 68, 26.7, and 78.4 days, respectively. Extracranial injuries including bone fractures were the most common associated injuries and medical complications such as spasticity and contractures were present in more than half of the patients.TBI survivors in this study made statistically significant functional improvements. Discharge FIM were significantly correlated with the admission FIM, durations of acute hospital stay and coma, and time since TBI. Multiple regression analysis of the data disclosed that FIM score obtained at the time of discharge from rehabilitation service was best predicted by two variables, time since brain injury and the FIM score at admission (multiple R=0.78, R=0.60, P<0.001). This sample of Turkish TBI survivors showed significant functional improvements after rehabilitation and admission functional status and the time since TBI had the most impact on discharge functional outcome.     

Validation of a model for evaluating outcome after traumatic brain injury

OBJECTIVE: To validate a model that examines the contribution of premorbid variables, injury severity, and functional and cognitive status to outcome 1 year after traumatic brain injury (TBI). DESIGN: Cross-validation study using a larger, national, prospective, longitudinal sample. SETTING: Acute inpatient rehabilitation hospitals at Traumatic Brain Injury Model Systems centers. PARTICIPANTS: Two sample populations followed through acute rehabilitation to 1 year after TBI. The original sample included 107 patients, and the cross-validation sample included 294 patients. Participants were predominantly young men who had experienced moderate to severe TBI in motor vehicle crashes. INTERVENTIONS: Acute medical and rehabilitation care. MAIN OUTCOME MEASURES: Disability Rating Scale, Community Integration Questionnaire, and return to employment. RESULTS: Structural equation modeling was used to compare the fit of the data to a path analysis developed through clinical use and previous research. Both samples provided adequate goodness of fit, supporting the model's validity. Injury severity affected cognitive and functional status, and cognitive and functional status significantly influenced 1-year outcome. Premorbid factors and injury severity did not directly influence outcome. CONCLUSIONS: Both samples supported the proposed model, which was cross-validated. Injury severity indirectly influences outcome through its effects on cognitive and functional status. Although treatment to decrease injury severity is obviously important, concentrated rehabilitation interventions aimed at improving patients' cognitive and functional status may have a more significant impact on 1-year outcome and should be the focus of future research.