Functional networks reemerge during recovery of consciousness after acute severe traumatic brain injury

Integrity of the default mode network (DMN) is believed to be essential for human consciousness. However, the effects of acute severe traumatic brain injury (TBI) on DMN functional connectivity are poorly understood. Furthermore, the temporal dynamics of DMN reemergence during recovery of consciousness have not been studied longitudinally in patients with acute severe TBI. We performed resting-state functional magnetic resonance imaging (rs-fMRI) to measure DMN connectivity in 17 patients admitted to the intensive care unit (ICU) with acute severe TBI and in 16 healthy control subjects. Eight patients returned for follow-up rs-fMRI and behavioral assessment six months post-injury. At each time point, we analyzed DMN connectivity by measuring intra-network correlations (i.e. positive correlations between DMN nodes) and inter-network anticorrelations (i.e. negative correlations between the DMN and other resting-state networks). All patients were comatose upon arrival to the ICU and had a disorder of consciousness (DoC) at the time of acute rs-fMRI (9.2 ± 4.6 days post-injury): 2 coma, 4 unresponsive wakefulness syndrome, 7 minimally conscious state, and 4 post-traumatic confusional state. We found that, while DMN anticorrelations were absent in patients with acute DoC, patients who recovered from coma to a minimally conscious or confusional state while in the ICU showed partially preserved DMN correlations. Patients who remained in coma or unresponsive wakefulness syndrome in the ICU showed no DMN correlations. All eight patients assessed longitudinally recovered beyond the confusional state by 6 months post-injury and showed normal DMN correlations and anticorrelations, indistinguishable from those of healthy subjects. Collectively, these findings suggest that recovery of consciousness after acute severe TBI is associated with partial preservation of DMN correlations in the ICU, followed by long-term normalization of DMN correlations and anticorrelations. Both intra-network DMN correlations and inter-network DMN anticorrelations may be necessary for full recovery of consciousness after acute severe TBI.

Practice guideline update recommendations summary: Disorders of consciousness: Report of the Guideline Development, Dissemination, and Implementation Subcommittee of the American Academy of Neurology; the American Congress of Rehabilitation Medicine; and the National Institute on Disability, Independent Living, and Rehabilitation Research

OBJECTIVE

To update the 1995 American Academy of Neurology (AAN) practice parameter on persistent vegetative state and the 2002 case definition on minimally conscious state (MCS) and provide care recommendations for patients with prolonged disorders of consciousness (DoC).

METHODS

Recommendations were based on systematic review evidence, related evidence, care principles, and inferences using a modified Delphi consensus process according to the AAN 2011 process manual, as amended.

RECOMMENDATIONS

Clinicians should identify and treat confounding conditions, optimize arousal, and perform serial standardized assessments to improve diagnostic accuracy in adults and children with prolonged DoC (Level B). Clinicians should counsel families that for adults, MCS (vs vegetative state [VS]/unresponsive wakefulness syndrome [UWS]) and traumatic (vs nontraumatic) etiology are associated with more favorable outcomes (Level B). When prognosis is poor, long-term care must be discussed (Level A), acknowledging that prognosis is not universally poor (Level B). Structural MRI, SPECT, and the Coma Recovery Scale-Revised can assist prognostication in adults (Level B); no tests are shown to improve prognostic accuracy in children. Pain always should be assessed and treated (Level B) and evidence supporting treatment approaches discussed (Level B). Clinicians should prescribe amantadine (100-200 mg bid) for adults with traumatic VS/UWS or MCS (4-16 weeks post injury) to hasten functional recovery and reduce disability early in recovery (Level B). Family counseling concerning children should acknowledge that natural history of recovery, prognosis, and treatment are not established (Level B). Recent evidence indicates that the term chronic VS/UWS should replace permanent VS, with duration specified (Level B). Additional recommendations are included.

Practice Guideline Update Recommendations Summary: Disorders of Consciousness: Report of the Guideline Development, Dissemination, and Implementation Subcommittee of the American Academy of Neurology; the American Congress of Rehabilitation Medicine; and the National Institute on Disability, Independent Living, and Rehabilitation Research

OBJECTIVE

To update the 1995 American Academy of Neurology (AAN) practice parameter on persistent vegetative state and the 2002 case definition on minimally conscious state (MCS) and provide care recommendations for patients with prolonged disorders of consciousness (DoC).

METHODS

Recommendations were based on systematic review evidence, related evidence, care principles, and inferences using a modified Delphi consensus process according to the AAN 2011 process manual, as amended.

RECOMMENDATIONS

Clinicians should identify and treat confounding conditions, optimize arousal, and perform serial standardized assessments to improve diagnostic accuracy in adults and children with prolonged DoC (Level B). Clinicians should counsel families that for adults, MCS (vs vegetative state [VS]/ unresponsive wakefulness syndrome [UWS]) and traumatic (vs nontraumatic) etiology are associated with more favorable outcomes (Level B). When prognosis is poor, long-term care must be discussed (Level A), acknowledging that prognosis is not universally poor (Level B). Structural MRI, SPECT, and the Coma Recovery Scale-Revised can assist prognostication in adults (Level B); no tests are shown to improve prognostic accuracy in children. Pain always should be assessed and treated (Level B) and evidence supporting treatment approaches discussed (Level B). Clinicians should prescribe amantadine (100-200 mg bid) for adults with traumatic VS/UWS or MCS (4-16 weeks post injury) to hasten functional recovery and reduce disability early in recovery (Level B). Family counseling concerning children should acknowledge that natural history of recovery, prognosis, and treatment are not established (Level B). Recent evidence indicates that the term chronic VS/UWS should replace permanent VS, with duration specified (Level B). Additional recommendations are included.

Comprehensive systematic review update summary: Disorders of consciousness: Report of the Guideline Development, Dissemination, and Implementation Subcommittee of the American Academy of Neurology; the American Congress of Rehabilitation Medicine; and the National Institute on Disability, Independent Living, and Rehabilitation Research

OBJECTIVE

To update the 1995 American Academy of Neurology (AAN) practice parameter on persistent vegetative state and the 2002 case definition for the minimally conscious state (MCS) by reviewing the literature on the diagnosis, natural history, prognosis, and treatment of disorders of consciousness lasting at least 28 days.

METHODS

Articles were classified per the AAN evidence-based classification system. Evidence synthesis occurred through a modified Grading of Recommendations Assessment, Development and Evaluation process. Recommendations were based on evidence, related evidence, care principles, and inferences according to the AAN 2011 process manual, as amended.

RESULTS

No diagnostic assessment procedure had moderate or strong evidence for use. It is possible that a positive EMG response to command, EEG reactivity to sensory stimuli, laser-evoked potentials, and the Perturbational Complexity Index can distinguish MCS from vegetative state/unresponsive wakefulness syndrome (VS/UWS). The natural history of recovery from prolonged VS/UWS is better in traumatic than nontraumatic cases. MCS is generally associated with a better prognosis than VS (conclusions of low to moderate confidence in adult populations), and traumatic injury is generally associated with a better prognosis than nontraumatic injury (conclusions of low to moderate confidence in adult and pediatric populations). Findings concerning other prognostic features are stratified by etiology of injury (traumatic vs nontraumatic) and diagnosis (VS/UWS vs MCS) with low to moderate degrees of confidence. Therapeutic evidence is sparse. Amantadine probably hastens functional recovery in patients with MCS or VS/UWS secondary to severe traumatic brain injury over 4 weeks of treatment. Recommendations are presented separately.

The Feasibility of Telephone-Administered Cognitive Testing in Individuals 1 and 2 Years after Inpatient Rehabilitation for Traumatic Brain Injury

Traumatic brain injury (TBI) often results in cognitive impairment, and trajectories of cognitive functioning can vary tremendously over time across survivors. Traditional approaches to measuring cognitive performance require face-to-face administration of a battery of objective neuropsychological tests, which can be time- and labor-intensive. There are numerous clinical and research contexts in which in-person testing is undesirable or unfeasible, including clinical monitoring of older adults or individuals with disability for whom travel is challenging, and epidemiological studies of geographically dispersed participants. A telephone-based method for measuring cognition could conserve resources and improve efficiency. The objective of this study is to examine the feasibility and usefulness of the Brief Test of Adult Cognition by Telephone (BTACT) among individuals who are 1 and 2 years post-moderate-to-severe TBI. A total of 463 individuals participated in the study at Year 1 post-injury, and 386 participated at Year 2. The sample was mostly male (73%) and white (59%), with an average age of (mean ± standard deviation) 47.9 ± 20.9 years, and 73% experienced a duration of post-traumatic amnesia (PTA) greater than 7 days. A majority of participants were able to complete the BTACT subtests (61-69% and 56-64% for Years 1 and 2 respectively); score imputation for those unable to complete a test due to severity of cognitive impairment yields complete data for 74-79% of the sample. BTACT subtests showed expected changes between Years 1-2, and summary scores demonstrated expected associations with injury severity, employment status, and cognitive status as measured by the Functional Independence Measure. Results indicate it is feasible, efficient, and useful to measure cognition over the telephone among individuals with moderate-severe TBI.

Examining Driving and Participation 5 Years After Traumatic Brain Injury

Participation is often considered a primary goal of traumatic brain injury (TBI) rehabilitation, but little is known about the influence of driving on participation after TBI. The objective of this study was to examine the independent contribution of driving status to participation at 5 years post TBI, after controlling for demographic, psychosocial, and functional factors. Participants ( N = 2,456) were community-dwelling individuals with moderate to severe TBI, age 18 to 65 at time of injury, and enrolled in the TBI Model Systems (TBIMS) National Database (NDB). Hierarchical linear regressions for the dependent variable of participation at 5 years post TBI were performed. Findings showed that driving was a highly significant independent predictor of participation and was a stronger relative predictor of participation than FIM® Cognitive, FIM® Motor, and depression. The independent contribution of driving to participation suggests the need to develop evidenced-based occupational therapy assessments and interventions that facilitate safe engagement in the occupation of driving to address the long-term goal of improved participation.

Abstract WMP16: Elevated Cerebral Neurite Orientation Dispersion and Density Imaging and Diffusion Kurtosis Values Are Associated With Poor Neurologic Outcome in Comatose Cardiac Arrest Patients

Background: For cardiac arrest survivors initially comatose after restoration of spontaneous circulation (ROSC), the extent of brain injury and expected neurologic outcome are crucial for patient management decisions. Advanced diffusion imaging approaches such as neurite orientation dispersion and density imaging (NODDI) or diffusion kurtosis imaging may provide additional insight into tissue integrity and potential for recovery of consciousness complementary to standard diffusion tensor imaging (DTI).

Methods: Multi-shell diffusion imaging was acquired in a prospective study of comatose cardiac arrest patients and in 5 controls. Neurite orientation dispersion (OD), intracellular volume fraction (ICVF), mean kurtosis (MK), axial kurtosis (AK), radial kurtosis (RK), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD) and fractional anisotropy (FA) were calculated. Median whole-brain values in patients with poor outcomes (no arousal recovery [AR] by discharge) were compared with those with AR and to controls (1-way ANOVA, post-hoc 1-sided Wilcoxon exact test).

Results: 18 patients (mean ±SD 48±23 y, 39% men) and 5 controls (37±19 y, 40% men) were analyzed. Median (range) Glasgow Coma Scale was 3 [3-5]. 10 patients exhibited AR, 8 did not. Median [IQR] time-to-MRI was 5 [4-8] days. FA (P=0.009), MK (P=0.017), AK (P=0.026), RK (P=0.014), OD (P=0.018) and ICVF (P=0.0038) were significantly different (see Figure). FA control values were greater than AR and no AR (P<0.05). MK, AK, RK, OD and ICVF values in the no AR group were greater than in the AR and control groups (P<0.05).

Discussion: This is the first report investigating early NODDI and diffusional heterogeneity changes in post-cardiac arrest comatose patients. Patients who failed to recover arousal demonstrated greater values for all kurtosis and NODDI metrics compared to controls. Potential bias from early withdrawal of life sustaining treatment and small cohorts are limitations.

Functional MRI Motor Imagery Tasks to Detect Command Following in Traumatic Disorders of Consciousness

Severe traumatic brain injury impairs arousal and awareness, the two components of consciousness. Accurate diagnosis of a patient’s level of consciousness is critical for determining treatment goals, access to rehabilitative services, and prognosis. The bedside behavioral examination, the current clinical standard for diagnosis of disorders of consciousness, is prone to misdiagnosis, a finding that has led to the development of advanced neuroimaging techniques aimed at detection of conscious awareness. Although a variety of paradigms have been used in functional magnetic resonance imaging (fMRI) to reveal covert consciousness, the relative accuracy of these paradigms in the patient population is unknown. Here, we compare the rate of covert consciousness detection by hand squeezing and tennis playing motor imagery paradigms in 10 patients with traumatic disorders of consciousness [six male, six acute, mean ± SD age = 27.9 ± 9.1 years, one coma, four unresponsive wakefulness syndrome, two minimally conscious without language function, and three minimally conscious with language function, per bedside examination with the Coma Recovery Scale-Revised (CRS-R)]. We also tested the same paradigms in 10 healthy subjects (nine male, mean ± SD age = 28.5 ± 9.4 years). In healthy subjects, the hand squeezing paradigm detected covert command following in 7/10 and the tennis playing paradigm in 9/10 subjects. In patients who followed commands on the CRS-R, the hand squeezing paradigm detected covert command following in 2/3 and the tennis playing paradigm in 0/3 subjects. In patients who did not follow commands on the CRS-R, the hand squeezing paradigm detected command following in 1/7 and the tennis playing paradigm in 2/7 subjects. The sensitivity, specificity, and accuracy (ACC) of detecting covert command following in patients who demonstrated this behavior on the CRS-R was 66.7, 85.7, and 80% for the hand squeezing paradigm and 0, 71.4, and 50% for the tennis playing paradigm, respectively. Overall, the tennis paradigm performed better than the hand squeezing paradigm in healthy subjects, but in patients, the hand squeezing paradigm detected command following with greater ACC. These findings indicate that current fMRI motor imagery paradigms frequently fail to detect command following and highlight the need for paradigm optimization to improve the accuracy of covert consciousness detection.

Early detection of consciousness in patients with acute severe traumatic brain injury

See Schiff (doi:10.1093/awx209) for a scientific commentary on this article. Patients with acute severe traumatic brain injury may recover consciousness before self-expression. Without behavioural evidence of consciousness at the bedside, clinicians may render an inaccurate prognosis, increasing the likelihood of withholding life-sustaining therapies or denying rehabilitative services. Task-based functional magnetic resonance imaging and electroencephalography techniques have revealed covert consciousness in the chronic setting, but these techniques have not been tested in the intensive care unit. We prospectively enrolled 16 patients admitted to the intensive care unit for acute severe traumatic brain injury to test two hypotheses: (i) in patients who lack behavioural evidence of language expression and comprehension, functional magnetic resonance imaging and electroencephalography detect command-following during a motor imagery task (i.e. cognitive motor dissociation) and association cortex responses during language and music stimuli (i.e. higher-order cortex motor dissociation); and (ii) early responses to these paradigms are associated with better 6-month outcomes on the Glasgow Outcome Scale-Extended. Patients underwent functional magnetic resonance imaging on post-injury Day 9.2 ± 5.0 and electroencephalography on Day 9.8 ± 4.6. At the time of imaging, behavioural evaluation with the Coma Recovery Scale-Revised indicated coma (n = 2), vegetative state (n = 3), minimally conscious state without language (n = 3), minimally conscious state with language (n = 4) or post-traumatic confusional state (n = 4). Cognitive motor dissociation was identified in four patients, including three whose behavioural diagnosis suggested a vegetative state. Higher-order cortex motor dissociation was identified in two additional patients. Complete absence of responses to language, music and motor imagery was only observed in coma patients. In patients with behavioural evidence of language function, responses to language and music were more frequently observed than responses to motor imagery (62.5-80% versus 33.3-42.9%). Similarly, in 16 matched healthy subjects, responses to language and music were more frequently observed than responses to motor imagery (87.5-100% versus 68.8-75.0%). Except for one patient who died in the intensive care unit, all patients with cognitive motor dissociation and higher-order cortex motor dissociation recovered beyond a confusional state by 6 months. However, 6-month outcomes were not associated with early functional magnetic resonance imaging and electroencephalography responses for the entire cohort. These observations suggest that functional magnetic resonance imaging and electroencephalography can detect command-following and higher-order cortical function in patients with acute severe traumatic brain injury. Early detection of covert consciousness and cortical responses in the intensive care unit could alter time-sensitive decisions about withholding life-sustaining therapies.

Challenges and Pitfalls Associated with Diagnostic and Prognostic Applications of Functional Neuroimaging in Disorders of Consciousness

The diagnostic assessment of patients with disorder of consciousness is currently based on clinical testing at the bedside and prone to a high error rate in the assessment of the degree of conscious awareness. Investigation of more objective assessment strategies, such as the use of functional magnetic resonance imaging (fMRI) to detect conscious awareness, are becoming increasingly popular in the research community. However, inherent challenges to the use of fMRI threaten its validity as a diagnostic tool and will need to be resolved prior to its integration into the clinical setting. These challenges, which range from the heterogeneity of the patient sample to factors influencing data acquisition and biases in interpretation strategies, are discussed below. Recommendations aimed at mitigating some of the limitations are provided.

Detection and Interpretation of Impossible and Improbable Coma Recovery Scale-Revised Scores

OBJECTIVE

To determine the frequency with which specific Coma Recovery Scale-Revised (CRS-R) subscale scores co-occur as a means of providing clinicians and researchers with an empirical method of assessing CRS-R data quality.

DESIGN

We retrospectively analyzed CRS-R subscale scores in hospital inpatients diagnosed with disorders of consciousness (DOCs) to identify impossible and improbable subscore combinations as a means of detecting inaccurate and unusual scores. Impossible subscore combinations were based on violations of CRS-R scoring guidelines. To determine improbable subscore combinations, we relied on the Mahalanobis distance, which detects outliers within a distribution of scores. Subscore pairs that were not observed at all in the database (ie, frequency of occurrence=0%) were also considered improbable.

SETTING

Specialized DOC program and university hospital.

PARTICIPANTS

Patients diagnosed with DOCs (N=1190; coma: n=76, vegetative state: n=464, minimally conscious state: n=586, emerged from minimally conscious state: n=64; 794 men; mean age, 43±20y; traumatic etiology: n=747; time postinjury, 162±568d).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

Impossible and improbable CRS-R subscore combinations.

RESULTS

Of the 1190 CRS-R profiles analyzed, 4.7% were excluded because they met scoring criteria for impossible co-occurrence. Among the 1137 remaining profiles, 12.2% (41/336) of possible subscore combinations were classified as improbable.

CONCLUSIONS

Clinicians and researchers should take steps to ensure the accuracy of CRS-R scores. To minimize the risk of diagnostic error and erroneous research findings, we have identified 9 impossible and 36 improbable CRS-R subscore combinations. The presence of any one of these subscore combinations should trigger additional data quality review.

An Italian multicentre validation study of the coma recovery scale-revised

BACKGROUND

Rate of misdiagnosis of disorders of consciousness (DoC) can be reduced by employing validated clinical diagnostic tools, such as the Coma Recovery Scale-Revised (CRS-R). An Italian version of the CRS-R has been recently developed, but its applicability across different clinical settings, and its concurrent validity and diagnostic sensitivity have not been estimated yet.

AIM

To perform a multicentre validation study of the Italian version of the Coma Recovery Scale-Revised (CRS-R).

DESIGN

Analysis of inter-rater reliability, concurrent validity and diagnostic sensitivity of the scale.

SETTING

One Intensive Care Unit, 8 Post-acute rehabilitation centres and 2 Long-term facilities

POPULATION

Twenty-seven professionals (physicians, N.=11; psychologists, N.=5; physiotherapists, N.=3; speech therapists, N.=6; nurses, N.=2) from 11 Italian Centres.

METHODS

CRS-R and Disability Rating Scale (DRS) applied to 122 patients with clinical diagnosis of Vegetative State (VS) or Minimally Conscious State (MCS).

RESULTS

CRS-R has good-to-excellent inter-rater reliability for all subscales, particularly for the communication subscale. The Italian version of the CRS-R showed a high sensitivity and specificity in detecting MCS with reference to clinical consensus diagnosis. The CRS-R showed good concurrent validity with the Disability Rating Scale, which had very low specificity with reference to clinical consensus diagnosis.

CONCLUSIONS

The Italian version of the CRS-R is a valid scale for use from the sub-acute to chronic stages of DoC. It can be administered reliably by all members of the rehabilitation team with different specialties, levels of experience and settings.

CLINICAL REHABILITATION IMPACT

The present study promote use of the Italian version of the CRS-R to improve diagnosis of DoC patients, and plan tailored rehabilitation treatment.

Sensitivity and Specificity of the Coma Recovery Scale--Revised Total Score in Detection of Conscious Awareness

OBJECTIVE

To describe the sensitivity and specificity of Coma Recovery Scale-Revised (CRS-R) total scores in detecting conscious awareness.

DESIGN

Data were retrospectively extracted from the medical records of patients enrolled in a specialized disorders of consciousness (DOC) program. Sensitivity and specificity analyses were completed using CRS-R-derived diagnoses of minimally conscious state (MCS) or emerged from minimally conscious state (EMCS) as the reference standard for conscious awareness and the total CRS-R score as the test criterion. A receiver operating characteristic curve was constructed to demonstrate the optimal CRS-R total cutoff score for maximizing sensitivity and specificity.

SETTING

Specialized DOC program.

PARTICIPANTS

Patients enrolled in the DOC program (N=252, 157 men; mean age, 49y; mean time from injury, 48d; traumatic etiology, n=127; nontraumatic etiology, n=125; diagnosis of coma or vegetative state, n=70; diagnosis of MCS or EMCS, n=182).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Sensitivity and specificity of CRS-R total scores in detecting conscious awareness.

RESULTS

A CRS-R total score of 10 or higher yielded a sensitivity of .78 for correct identification of patients in MCS or EMCS, and a specificity of 1.00 for correct identification of patients who did not meet criteria for either of these diagnoses (ie, were diagnosed with vegetative state or coma). The area under the curve in the receiver operating characteristic curve analysis is .98.

CONCLUSIONS

A total CRS-R score of 10 or higher provides strong evidence of conscious awareness but resulted in a false-negative diagnostic error in 22% of patients who demonstrated conscious awareness based on CRS-R diagnostic criteria. A cutoff score of 8 provides the best balance between sensitivity and specificity, accurately classifying 93% of cases. The optimal total score cutoff will vary depending on the user's objective.

GABAA receptor deficits predict recovery in patients with disorders of consciousness: A preliminary multimodal [(11) C]Flumazenil PET and fMRI study

OBJECTIVES

Disorders of consciousness (DoC)-that is, unresponsive wakefulness syndrome/vegetative state and minimally conscious state-are debilitating conditions for which no reliable markers of consciousness recovery have yet been identified. Evidence points to the GABAergic system being altered in DoC, making it a potential target as such a marker.

EXPERIMENTAL DESIGN

In our preliminary study, we used [(11) C]Flumazenil positron emission tomography to establish global GABAA receptor binding potential values and the local-to-global (LTG) ratio of these for specific regions. These values were then compared between DoC patients and healthy controls. In addition, they were correlated with behavioral improvements for the patients between the time of scanning and 3 months later. Functional magnetic resonance imaging resting-state functional connectivity was also calculated and the same comparisons made.

PRINCIPAL OBSERVATIONS

lobal GABAA receptor binding was reduced in DoC, as was the LTG ratio in specifically the supragenual anterior cingulate. Both of these measures correlated with behavioral improvement after 3 months. In contrast to these measures of GABAA receptor binding, functional connectivity did not correlate with behavioral improvement.

CONCLUSIONS

Our preliminary findings point toward GABAA receptor binding being a marker of consciousness recovery in DoC.

Clinical management of the minimally conscious state

The minimally conscious state (MCS) was defined as a disorder of consciousness (DoC) distinct from the vegetative state more than a decade ago. While this condition has become widely recognized, there are still no guidelines to steer the approach to assessment and treatment. The development of evidence-based practice guidelines for MCS has been hampered by ambiguity around the concept of consciousness, the lack of accurate methods of assessment, and the dearth of well-designed clinical trials. This chapter provides a critical review of existing assessment procedures, critically reviews available treatment options and identifies knowledge gaps. We close with practice-based recommendations for a rational approach to clinical management of this challenging population.

A multicentre study of intentional behavioural responses measured using the Coma Recovery Scale-Revised in patients with minimally conscious state

OBJECTIVE

To investigate which conscious behaviour is most frequently detected using the Coma Recovery Scale-Revised in patients with minimally conscious state.

DESIGN

Multicentre, cross-sectional study.

SETTING

One intensive care unit, 8 post-acute rehabilitation centres and 2 long-term facilities.

SUBJECTS

Fifty-two patients with established diagnosis of minimally conscious state of different aetiology.

MAIN MEASURES

All patients were assessed by the Coma Recovery Scale-Revised.

RESULTS

In most patients (34/52) non-reflexive responses were identified by two or more subscales of the Coma Recovery Scale-Revised, whereas in 14 patients only the visual subscale could identify cortically-mediated behaviours, and in the remaining 4 patients only the motor subscale did so.The clinical signs of intentional behaviour were most often detected by the visual subscale (43/52 patients) and by the motor subscale (31/52), and least frequently by the oromotor/verbal subscale (3/52) of the Coma Recovery Scale-Revised. This clinical pattern was observed independently from time post-onset and aetiology.

CONCLUSIONS

Non-reflexive visual behaviour, identified by the visual subscale of Coma Recovery Scale-Revised, is the most frequently detected intentional sign consistent with the diagnosis of minimally conscious state, independently from aetiology and time post-onset.

Preserved Covert Cognition in Noncommunicative Patients With Severe Brain Injury?

Background. Despite recent evidence suggesting that some severely brain-injured patients retain some capacity for top-down processing (covert cognition), the degree of sparing is unknown. Objective. Top-down attentional processing was assessed in patients in minimally conscious (MCS) and vegetative states (VS) using an active event-related potential (ERP) paradigm. Methods. A total of 26 patients were included (38 ± 12 years old, 9 traumatic, 21 patients >1 year postonset): 8 MCS+, 8 MCS−, and 10 VS patients. There were 14 healthy controls (30 ± 8 years old). The ERP paradigm included (1) a passive condition and (2) an active condition, wherein the participant was instructed to voluntarily focus attention on his/her own name. In each condition, the participant’s own name was presented 100 times (ie, 4 blocks of 25 stimuli). Results. In 5 MCS+ patients as well as in 3 MCS− patients and 1 VS patient, an enhanced P3 amplitude was observed in the active versus passive condition. Relative to controls, patients showed a response that was (1) widely distributed over frontoparietal areas and (2) not present in all blocks (3 of 4). In patients with covert cognition, the amplitude of the response was lower in frontocentral electrodes compared with controls but did not differ from that in the MCS+ group. Conclusion. The results indicate that volitional top-down attention is impaired in patients with covert cognition. Further investigation is crucially needed to better understand top-down cognitive functioning in this population because this may help refine brain-computer interface–based communication strategies.

Unexpected recovery of function after severe traumatic brain injury: the limits of early neuroimaging-based outcome prediction

BACKGROUND

Prognostication in the early stage of traumatic coma is a common challenge in the neuro-intensive care unit. We report the unexpected recovery of functional milestones (i.e., consciousness, communication, and community reintegration) in a 19-year-old man who sustained a severe traumatic brain injury. The early magnetic resonance imaging (MRI) findings, at the time, suggested a poor prognosis.

METHODS

During the first year of the patient's recovery, MRI with diffusion tensor imaging and T2*-weighted imaging was performed on day 8 (coma), day 44 (minimally conscious state), day 198 (post-traumatic confusional state), and day 366 (community reintegration). Mean apparent diffusion coefficient (ADC) and fractional anisotropy values in the corpus callosum, cerebral hemispheric white matter, and thalamus were compared with clinical assessments using the Disability Rating Scale (DRS).

RESULTS

Extensive diffusion restriction in the corpus callosum and bihemispheric white matter was observed on day 8, with ADC values in a range typically associated with neurotoxic injury (230-400 × 10(-6 )mm(2)/s). T2*-weighted MRI revealed widespread hemorrhagic axonal injury in the cerebral hemispheres, corpus callosum, and brainstem. Despite the presence of severe axonal injury on early MRI, the patient regained the ability to communicate and perform activities of daily living independently at 1 year post-injury (DRS = 8).

CONCLUSIONS

MRI data should be interpreted with caution when prognosticating for patients in traumatic coma. Recovery of consciousness and community reintegration are possible even when extensive traumatic axonal injury is demonstrated by early MRI.

Impaired consciousness in partial seizures is bimodally distributed

OBJECTIVE

To investigate whether impaired consciousness in partial seizures can usually be attributed to specific deficits in the content of consciousness or to a more general decrease in the overall level of consciousness.

METHODS

Prospective testing during partial seizures was performed in patients with epilepsy using the Responsiveness in Epilepsy Scale (n = 83 partial seizures, 30 patients). Results were compared with responsiveness scores in a cohort of patients with severe traumatic brain injury evaluated with the JFK Coma Recovery Scale-Revised (n = 552 test administrations, 184 patients).

RESULTS

Standardized testing during partial seizures reveals a bimodal scoring distribution, such that most patients were either fully impaired or relatively spared in their ability to respond on multiple cognitive tests. Seizures with impaired performance on initial test items remained consistently impaired on subsequent items, while other seizures showed spared performance throughout. In the comparison group, we found that scores of patients with brain injury were more evenly distributed across the full range in severity of impairment.

CONCLUSIONS

Partial seizures can often be cleanly separated into those with vs without overall impaired responsiveness. Results from similar testing in a comparison group of patients with brain injury suggest that the bimodal nature of Responsiveness in Epilepsy Scale scores is not a result of scale bias but may be a finding unique to partial seizures. These findings support a model in which seizures either propagate or do not propagate to key structures that regulate overall arousal and thalamocortical function. Future investigations are needed to relate these behavioral findings to the physiology underlying impaired consciousness in partial seizures.

Impact of aphasia on consciousness assessment: a cross-sectional study

BACKGROUND

Previous findings suggest that language disorders may occur in severely brain-injured patients and could interfere with behavioral assessments of consciousness. However, no study investigated to what extent language impairment could affect patients' behavioral responses. Objective. To estimate the impact of receptive and/or productive language impairments on consciousness assessment.

METHODS

Twenty-four acute and subacute stroke patients with different types of aphasia (global, n = 11; Broca, n = 4; Wernicke, n = 3; anomic, n = 4; mixed, n = 2) were recruited in neurology and neurosurgery units as well as in rehabilitation centers. The Coma Recovery Scale-Revised (CRS-R) was administered.

RESULTS

We observed that 25% (6 out of 24) of stroke patients with a diagnosis of aphasia and 54% (6 out of 11) of patients with a diagnosis of global aphasia did not reach the maximal CRS-R total score of 23. An underestimation of the consciousness level was observed in 3 patients with global aphasia who could have been misdiagnosed as being in a minimally conscious state, even in the absence of any documented period of coma. More precisely, lower subscores were observed on the communication, motor, oromotor, and arousal subscales.

CONCLUSION

Consciousness assessment may be complicated by the co-occurrence of severe language deficits. This stresses the importance of developing new tools or identifying items in existing scales, which may allow the detection of language impairment in severely brain-injured patients.

Functional MRI and outcome in traumatic coma

Advances in task-based functional MRI (fMRI), resting-state fMRI (rs-fMRI), and arterial spin labeling (ASL) perfusion MRI have occurred at a rapid pace in recent years. These techniques for measuring brain function have great potential to improve the accuracy of prognostication for civilian and military patients with traumatic coma. In addition, fMRI, rs-fMRI, and ASL perfusion MRI have provided novel insights into the pathophysiology of traumatic disorders of consciousness, as well as the mechanisms of recovery from coma. However, functional neuroimaging techniques have yet to achieve widespread clinical use as prognostic tests for patients with traumatic coma. Rather, a broad spectrum of methodological hurdles currently limits the feasibility of clinical implementation. In this review, we discuss the basic principles of fMRI, rs-fMRI, and ASL perfusion MRI and their potential applications as prognostic tools for patients with traumatic coma. We also discuss future strategies for overcoming the current barriers to clinical implementation.

Do rehospitalization rates differ among injury severity levels in the NIDRR Traumatic Brain Injury Model Systems program?

OBJECTIVE

To compare the rate and nature of rehospitalization in a cohort of patients enrolled in the National Institute on Disability and Rehabilitation Research Traumatic Brain Injury Model Systems (TBIMS) who have disorders of consciousness (DOC) at the time of rehabilitation admission with those in persons with moderate or severe traumatic brain injury (TBI) but without DOC at rehabilitation admission.

DESIGN

Prospective observational study.

SETTING

Inpatient rehabilitation within TBIMS with annual follow-up.

PARTICIPANTS

Of 9028 persons enrolled from 1988 to 2009 (N=9028), 366 from 20 centers met criteria for DOC at rehabilitation admission and follow-up data, and another 5132 individuals met criteria for moderate (n=769) or severe TBI (n=4363).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Participants and/or their family members completed follow-up data collection including questions about frequency and nature of rehospitalizations at 1 year postinjury. For the subset of participants with DOC, additional follow-up was conducted at 2 and 5 years postinjury.

RESULTS

The DOC group demonstrated an overall 2-fold increase in rehospitalization in the first year postinjury relative to those with moderate or severe TBI without DOC. Persons with DOC at rehabilitation admission have a higher rate of rehospitalization across several categories than persons with moderate or severe TBI.

CONCLUSIONS

Although the specific details of rehospitalization are unknown, greater injury severity resulting in DOC status on rehabilitation admission has long-term implications. Data highlight the need for a longitudinal approach to patient management.

Functional outcomes in traumatic disorders of consciousness: 5-year outcomes from the National Institute on Disability and Rehabilitation Research Traumatic Brain Injury Model Systems

OBJECTIVE

To characterize the 5-year outcomes of patients with traumatic brain injury (TBI) not following commands when admitted to acute inpatient rehabilitation.

DESIGN

Secondary analysis of prospectively collected data from the National Institute on Disability and Rehabilitation Research-funded Traumatic Brain Injury Model Systems (TBIMS).

SETTING

Inpatient rehabilitation hospitals participating in the TBIMS program.

PARTICIPANTS

Patients (N=108) with TBI not following commands at admission to acute inpatient rehabilitation were divided into 2 groups (early recovery: followed commands before discharge [n=72]; late recovery: did not follow commands before discharge [n=36]).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

FIM items.

RESULTS

For the early recovery group, depending on the FIM item, 8% to 21% of patients were functioning independently at discharge, increasing to 56% to 85% by 5 years postinjury. The proportion functioning independently increased from discharge to 1 year, 1 to 2 years, and 2 to 5 years. In the late recovery group, depending on the FIM item, 19% to 36% of patients were functioning independently by 5 years postinjury. The proportion of independent patients increased significantly from discharge to 1 year and from 1 to 2 years, but not from 2 to 5 years.

CONCLUSIONS

Substantial proportions of patients admitted to acute inpatient rehabilitation before following commands recover independent functioning over as long as 5 years, particularly if they begin to follow commands before hospital discharge.

Prospective assessment of ictal behavior using the revised Responsiveness in Epilepsy Scale (RES-II)

Impaired consciousness in epilepsy has a significant negative impact on patients' quality of life yet is difficult to study objectively. Here, we develop an improved prospective Responsiveness in Epilepsy Scale-II (RES-II) and report initial results compared with the earlier version of the scale (RES). The RES-II is simpler to administer and includes both verbal and non-verbal test items. We evaluated 75 seizures (24 patients) with RES and 34 seizures (11 patients) with RES-II based on video-EEG review. The error rate per seizure by test administrators improved markedly from a mean of 2.01 ± 0.04 with RES to 0.24 ± 0.11 with RES-II. Performance during focal seizures showed a bimodal distribution, corresponding to the traditional complex partial vs. simple partial seizure classification. We conclude that RES-II has improved accuracy and testing efficiency compared with the original RES. Prospective objective testing will ultimately lead to a better understanding of the mechanisms of impaired consciousness in epilepsy.

Testing for minimal consciousness in complex partial and generalized tonic-clonic seizures

Impaired consciousness in epilepsy has a major negative impact on quality of life. Prior work suggests that complex partial seizures (CPS) and generalized tonic-clonic seizures (GTCS), which both cause loss of consciousness, affect similar frontoparietal networks. Milder involvement in CPS than in GTCS may spare some simple behavioral responses, resembling the minimally conscious state. However, this difference in responses has not been rigorously tested previously. During video-electroencephalography (EEG) monitoring, we administered a standardized prospective testing battery including responses to questions and commands, as well as tests for reaching/grasping a ball and visual tracking in 27 CPS (in 14 patients) and 7 GTCS (in six patients). Behavioral results were analyzed in the ictal and postictal periods based on video review. During both CPS and GTCS, patients were unable to respond to questions or commands. However, during CPS, patients often retained minimally conscious ball grasping and visual tracking responses. Patients were able to successfully grasp a ball in 60% or to visually track in 58% of CPS, and could carry out both activities in 52% of CPS. In contrast, during GTCS, preserved ball grasp (10%), visual tracking (11%), or both (7%), were all significantly less than in CPS. Postictal ball grasping and visual tracking were also somewhat better following CPS than GTCS. These findings suggest that impaired consciousness in CPS is more similar to minimally conscious state than to coma. Further work may elucidate the specific brain networks underlying relatively spared functions in CPS, ultimately leading to improved treatments aimed at preventing impaired consciousness.

Placebo-controlled trial of amantadine for severe traumatic brain injury

BACKGROUND

Amantadine hydrochloride is one of the most commonly prescribed medications for patients with prolonged disorders of consciousness after traumatic brain injury. Preliminary studies have suggested that amantadine may promote functional recovery.

METHODS

We enrolled 184 patients who were in a vegetative or minimally conscious state 4 to 16 weeks after traumatic brain injury and who were receiving inpatient rehabilitation. Patients were randomly assigned to receive amantadine or placebo for 4 weeks and were followed for 2 weeks after the treatment was discontinued. The rate of functional recovery on the Disability Rating Scale (DRS; range, 0 to 29, with higher scores indicating greater disability) was compared over the 4 weeks of treatment (primary outcome) and during the 2-week washout period with the use of mixed-effects regression models.

RESULTS

During the 4-week treatment period, recovery was significantly faster in the amantadine group than in the placebo group, as measured by the DRS score (difference in slope, 0.24 points per week; P=0.007), indicating a benefit with respect to the primary outcome measure. In a prespecified subgroup analysis, the treatment effect was similar for patients in a vegetative state and those in a minimally conscious state. The rate of improvement in the amantadine group slowed during the 2 weeks after treatment (weeks 5 and 6) and was significantly slower than the rate in the placebo group (difference in slope, 0.30 points per week; P=0.02). The overall improvement in DRS scores between baseline and week 6 (2 weeks after treatment was discontinued) was similar in the two groups. There were no significant differences in the incidence of serious adverse events.

CONCLUSIONS

Amantadine accelerated the pace of functional recovery during active treatment in patients with post-traumatic disorders of consciousness. (Funded by the National Institute on Disability and Rehabilitation Research; ClinicalTrials.gov number, NCT00970944.).

Impaired consciousness in epilepsy investigated by a prospective responsiveness in epilepsy scale (RES)

PURPOSE

Impaired consciousness in epileptic seizures has a major negative impact on patient quality of life. Prior work on epileptic unconsciousness has mainly used retrospective and nonstandardized methods. Our goal was to validate and to obtain initial data using a standardized prospective testing battery.

METHODS

The responsiveness in epilepsy scale (RES) was used on 52 patients during continuous video-electroencephalography (EEG) monitoring. RES begins with higher-level questions and commands, and switches adaptively to more basic sensorimotor responses depending on patient performance. RES continues after seizures and includes postictal memory testing. Scoring was conducted based on video review.

KEY FINDINGS

Testing on standardized seizure simulations yielded good intrarater and interrater reliability. We captured 59 seizures from 18 patients (35% of participants) during 1,420 h of RES monitoring. RES impairment was greatest during and after tonic-clonic seizures, less in partial seizures, and minimal in auras and subclinical seizures. In partial seizures, ictal RES impairment was significantly greater if EEG changes were present. Maximum RES impairment (lowest ictal score) was also significantly correlated with long postictal recovery time, and poor postictal memory.

SIGNIFICANCE

We found that prospective testing of responsiveness during seizures is feasible and reliable. RES impairment was related to EEG changes during seizures, as well as to postictal memory deficits and recovery time. With a larger patient sample it is hoped that this approach can identify brain networks underlying specific components of impaired consciousness in seizures. This may allow the development of improved treatments targeted at preventing dysfunction in these networks.

Longitudinal outcome of patients with disordered consciousness in the NIDRR TBI Model Systems Programs

Few studies address the course of recovery from prolonged disorders of consciousness (DOC) after severe traumatic brain injury (TBI). This study examined acute and long-term outcomes of persons with DOC admitted to acute inpatient rehabilitation within the National Institute on Disability and Rehabilitation Research (NIDRR) TBI Model Systems Programs (TBIMS). Of 9028 persons enrolled from 1988 to 2009, 396 from 20 centers met study criteria. Participants were primarily male (73%), Caucasian (67%), injured in motor vehicle collision (66%), with a median age of 28, and emergency department Glasgow Coma Scale (GCS) score of 3. Participant status was evaluated at acute rehabilitation admission and discharge and at 1, 2, and 5 years post-injury. During inpatient rehabilitation, 268 of 396 (68%) regained consciousness and 91 (23%) emerged from post-traumatic amnesia (PTA). Participants demonstrated significant improvements on GCS (z=16.135, p≤0.001) and Functional Independence Measure (FIM) (z=15.584, p≤0.001) from rehabilitation admission (median GCS=9; FIM=18) to discharge (median GCS=14; FIM=43). Of 337 with at least one follow-up visit, 28 (8%) had died by 2.1 years (mean) after discharge. Among survivors, 66 (21%) improved to become capable of living without in-house supervision, and 63 demonstrated employment potential using the Disability Rating Scale (DRS). Participants with follow-up data at 1, 2, and 5 years post-injury (n=108) demonstrated significant improvement across all follow-up evaluations on the FIM Cognitive and Supervision Rating Scale (p<0.01). Significant improvements were observed on the DRS and FIM Motor at 1 and 2 years post-injury (p<0.01). Persons with DOC at the time of admission to inpatient rehabilitation showed functional improvement throughout early recovery and in years post-injury.

Recommendations for the use of common outcome measures in traumatic brain injury research

This article summarizes the selection of outcome measures by the interagency Traumatic Brain Injury (TBI) Outcomes Workgroup to address primary clinical research objectives, including documentation of the natural course of recovery from TBI, prediction of later outcome, measurement of treatment effects, and comparison of outcomes across studies. Consistent with other Common Data Elements Workgroups, the TBI Outcomes Workgroup adopted the standard 3-tier system in its selection of measures. In the first tier, core measures included valid, robust, and widely applicable outcome measures with proven utility in TBI from each identified domain, including global level of function, neuropsychological impairment, psychological status, TBI-related symptoms, executive functions, cognitive and physical activity limitations, social role participation, and perceived health-related quality of life. In the second tier, supplemental measures were recommended for consideration in TBI research focusing on specific topics or populations. In the third tier, emerging measures included important instruments currently under development, in the process of validation, or nearing the point of published findings that have significant potential to be superior to some older ("legacy") measures in the core and supplemental lists and may eventually replace them as evidence for their utility emerges.

Behavioral assessment in patients with disorders of consciousness: gold standard or fool's gold?

In the absence of "hard" neurophysiologic markers, the burden of proof for establishing conscious awareness in individuals who sustain severe brain injury lies in behavioral assessment. Because behavior represents indirect evidence of consciousness, reliance on behavioral markers presents significant challenges and may lead to misdiagnosis. Detection of conscious awareness is confounded by numerous factors including fluctuations in arousal level, difficulty differentiating reflexive or involuntary movement from intentional behavior, underlying sensory and motor impairments, and medication side effects. When an ambiguous behavior is observed, the onus falls to the clinician to determine where along the continuum of unconsciousness to consciousness, it lies. This paper (1) summarizes the current diagnostic criteria for coma, the vegetative state, and the minimally conscious state, (2) describes current behavioral assessment methods, (3) discusses the limitations of behavioral assessment techniques, (4) reviews recent applications of functional neuroimaging in the assessment of patients with disorders of consciousness, and (5) concludes with a case study that illustrates the disparity between behavioral and functional neuroimaging findings that may be encountered in this population.

The predictive validity of a brief inpatient neuropsychologic battery for persons with traumatic brain injury

OBJECTIVE

To examine the predictive validity of a brief neuropsychologic test battery consisting of the Galveston Orientation and Amnesia Test, the California Verbal Learning Test-II, Trail-Making Test (TMT), Symbol Digit Modalities Test, grooved pegboard, phonemic and categorical word generation tasks, the Wechsler Test of Adult Reading (WTAR), and the Wisconsin Card Sorting Test-64 relative to functional outcome at 1 year in persons with traumatic brain injury.

DESIGN

Inception cohort study. Follow-up period of 12 months.

SETTING

Seven Traumatic Brain Injury Model System centers. Neuropsychologic testing was conducted during the acute inpatient rehabilitation stay and functional outcome measures were obtained at 1-year outpatient follow-up.

PARTICIPANTS

Adults (N=174) who met criteria for admission to inpatient brain injury rehabilitation.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

FIM instrument, Disability Rating Scale, Supervision Rating Scale, Satisfaction With Life Scale (SWLS), and Glasgow Outcome Scale-Extended.

RESULTS

Multiple regression analyses revealed that performance on the neuropsychologic test battery was predictive of outcome at 1 year postinjury for all outcome measures, except FIM motor scores and the SWLS. Cognitive performance using this battery was found to predict 1-year outcomes above and beyond functional variables and injury severity variables collected during inpatient rehabilitation, thereby indicating incremental validity for this test battery. Individual tests that were found to be significant predictors of 1-year outcomes included the WTAR and TMT part B.

CONCLUSIONS

These findings support the clinical utility and ecological validity of this battery with respect to level of disability, functional independence, and supervision required.

A case of locked-in syndrome complicated by central deafness

BACKGROUND

A 53-year-old male with a history of hypertension, diabetes mellitus, and factor V deficiency presented to an emergency room with progressively increasing headache, slurred speech, and left upper extremity weakness. Over the previous 3 months, he had been receiving warfarin for prophylaxis of deep venous thrombosis following knee surgery. After presentation and an initial period of coma, he became tetraplegic and anarthric, requiring intubation and ventilatory assistance.

INVESTIGATIONS

Neurological examination, CT scan, electroencephalogram, brainstem auditory and visual evoked potential studies, neuropsychological assessment and functional MRI studies.

DIAGNOSIS

Locked-in syndrome following ventral pontine hemorrhage, complicated by central deafness secondary to extension of the lesion to the inferior colliculus.

MANAGEMENT

Development of an augmentative communication system designed to exploit the patient's preserved cognitive and motor functions.

Recent advances in behavioral assessment of individuals with disorders of consciousness

PURPOSE OF REVIEW

The burden of proof for establishing diagnosis and prognosis in patients with disorders of consciousness lies with behavioral assessment methods. The current review discusses recent advances in understanding the strengths and weaknesses of this methodology.

RECENT FINDINGS

Behavioral assessment methods remain the 'gold standard' for establishing diagnosis and prognosis in patients with disorders of consciousness, although their psychometric integrity and clinical utility remain largely unproven. While the Glasgow Coma Scale maintains its standing in the trauma setting, there are ongoing concerns regarding testing confounds and interrater reliability. The Full Outline of UnResponsiveness, an emerging alternative, is more sensitive to detection of locked-in syndrome but may fail to identify patients in the minimally conscious state. Recent studies investigating the relationship between behavioral and neurophysiologic measures of conscious awareness have revealed important dissociations between behavioral response profiles and corresponding neural activity.

SUMMARY

Further research is needed on the psychometric properties of existing behavioral assessment methods for disorders of consciousness. Although dissociations between behavioral and neurophysiologic findings caution against overreliance on behavioral metrics for detection of conscious awareness, we expect there will be increased effort toward combining these methodologies to increase diagnostic accuracy and prognostic specificity in patients with disorders of consciousness.

Behavioural improvements with thalamic stimulation after severe traumatic brain injury

Widespread loss of cerebral connectivity is assumed to underlie the failure of brain mechanisms that support communication and goal-directed behaviour following severe traumatic brain injury. Disorders of consciousness that persist for longer than 12 months after severe traumatic brain injury are generally considered to be immutable; no treatment has been shown to accelerate recovery or improve functional outcome in such cases. Recent studies have shown unexpected preservation of large-scale cerebral networks in patients in the minimally conscious state (MCS), a condition that is characterized by intermittent evidence of awareness of self or the environment. These findings indicate that there might be residual functional capacity in some patients that could be supported by therapeutic interventions. We hypothesize that further recovery in some patients in the MCS is limited by chronic underactivation of potentially recruitable large-scale networks. Here, in a 6-month double-blind alternating crossover study, we show that bilateral deep brain electrical stimulation (DBS) of the central thalamus modulates behavioural responsiveness in a patient who remained in MCS for 6 yr following traumatic brain injury before the intervention. The frequency of specific cognitively mediated behaviours (primary outcome measures) and functional limb control and oral feeding (secondary outcome measures) increased during periods in which DBS was on as compared with periods in which it was off. Logistic regression modelling shows a statistical linkage between the observed functional improvements and recent stimulation history. We interpret the DBS effects as compensating for a loss of arousal regulation that is normally controlled by the frontal lobe in the intact brain. These findings provide evidence that DBS can promote significant late functional recovery from severe traumatic brain injury. Our observations, years after the injury occurred, challenge the existing practice of early treatment discontinuation for patients with only inconsistent interactive behaviours and motivate further research to develop therapeutic interventions.

Functional neuroimaging applications for assessment and rehabilitation planning in patients with disorders of consciousness

OBJECTIVE

To describe the theoretic framework, design, and potential clinical applications of functional neuroimaging protocols in patients with disorders of consciousness.

DATA SOURCES

Recent published literature and authors' own work.

STUDY SELECTION

Studies using functional neuroimaging techniques to investigate cognitive processing in patients diagnosed with vegetative and minimally conscious state.

DATA EXTRACTION

Not applicable.

DATA SYNTHESIS

Positron-emission tomography activation studies suggest that the vegetative state represents a global disconnection syndrome in which higher order association cortices are functionally disconnected from primary cortical areas. In contrast, patterns of activation in functional magnetic resonance imaging studies of patients in the minimally conscious state show preservation of large-scale cortical networks associated with language and visual processing.

CONCLUSIONS

Novel applications of functional neuroimaging in patients with disorders of consciousness may aid in differential diagnosis, prognostic assessment and identification of pathophysiologic mechanisms. Improvements in patient characterization may, in turn, provide new opportunities for restoration of function through interventional neuromodulation.

How should functional imaging of patients with disorders of consciousness contribute to their clinical rehabilitation needs?

PURPOSE OF REVIEW

We discuss the problems of evidence-based neurorehabilitation in disorders of consciousness, and recent functional neuroimaging data obtained in the vegetative state and minimally conscious state.

RECENT FINDINGS

Published data are insufficient to make recommendations for or against any of the neurorehabilitative treatments in vegetative state and minimally conscious state patients. Electrophysiological and functional imaging studies have been shown to be useful in measuring residual brain function in noncommunicative brain-damaged patients. Despite the fact that such studies could in principle allow an objective quantification of the putative cerebral effect of rehabilitative treatment in the vegetative state and minimally conscious state, they have so far not been used in this context.

SUMMARY

Without controlled studies and careful patient selection criteria it will not be possible to evaluate the potential of therapeutic interventions in disorders of consciousness. There also is a need to elucidate the neurophysiological effects of such treatments. Integration of multimodal neuroimaging techniques should eventually improve our ability to disentangle differences in outcome on the basis of underlying mechanisms and better guide our therapeutic options in the challenging patient populations encountered following severe acute brain damage.

Possible axonal regrowth in late recovery from the minimally conscious state

We used diffusion tensor imaging (DTI) to study 2 patients with traumatic brain injury. The first patient recovered reliable expressive language after 19 years in a minimally conscious state (MCS); the second had remained in MCS for 6 years. Comparison of white matter integrity in the patients and 20 normal subjects using histograms of apparent diffusion constants and diffusion anisotropy identified widespread altered diffusivity and decreased anisotropy in the damaged white matter. These findings remained unchanged over an 18-month interval between 2 studies in the first patient. In addition, in this patient, we identified large, bilateral regions of posterior white matter with significantly increased anisotropy that reduced over 18 months. In contrast, notable increases in anisotropy within the midline cerebellar white matter in the second study correlated with marked clinical improvements in motor functions. This finding was further correlated with an increase in resting metabolism measured by PET in this subregion. Aberrant white matter structures were evident in the second patient's DTI images but were not clinically correlated. We propose that axonal regrowth may underlie these findings and provide a biological mechanism for late recovery. Our results are discussed in the context of recent experimental studies that support this inference.

The JFK Coma Recovery Scale--Revised

The JFK Coma Recovery Scale (CRS) was developed to help characterise and monitor patients functioning at Rancho Levels I-IV and has been used widely in both clinical and research settings within the US and Europe. The CRS was recently revised to address a number of concerns emanating from our own clinical experience with the scale, feedback from users and researchers as well as the results of Rasch analyses. Additionally, the CRS did not include all of the behavioural criteria necessary to diagnose the minimally conscious state (MCS), thereby limiting diagnostic utility. The revised JFK Coma Recovery Scale (CRS-R) includes addition of new items, merging of items found to be statistically similar, deletion or modification of items showing poor fit with the scale's underlying construct, renaming of items, more stringent scoring criteria, and quantification of elicited behaviours to improve accuracy of rating. Psychometric properties of the CRS-R appear to meet standards for measurement and evaluation tools for use in clinical and research settings, and diagnostic application suggests that the scale is capable of discriminating patients in the minimally conscious state from those in the vegetative state.

Evidence-based cognitive rehabilitation: updated review of the literature from 1998 through 2002

OBJECTIVE

To update the previous evidence-based recommendations of the Brain Injury Interdisciplinary Special Interest Group of the American Congress of Rehabilitation Medicine for cognitive rehabilitation of people with traumatic brain injury (TBI) and stroke, based on a systematic review of the literature from 1998 through 2002.

DATA SOURCES

PubMed and Infotrieve literature searches were conducted using the terms attention, awareness, cognition, communication, executive, language, memory, perception, problem solving, and reasoning combined with each of the terms rehabilitation, remediation, and training. Reference lists from identified articles were reviewed and a bibliography listing 312 articles was compiled.

STUDY SELECTION

One hundred eighteen articles were initially selected for inclusion. Thirty-one studies were excluded after detailed review. Excluded articles included 14 studies without data, 6 duplicate publications or follow-up studies, 5 nontreatment studies, 4 reviews, and 2 case studies involving diagnoses other than TBI or stroke.

DATA EXTRACTION

Articles were assigned to 1 of 7 categories reflecting the primary area of intervention: attention; visual perception; apraxia; language and communication; memory; executive functioning, problem solving and awareness; and comprehensive-holistic cognitive rehabilitation. Articles were abstracted and levels of evidence determined using specific criteria.

DATA SYNTHESIS

Of the 87 studies evaluated, 17 were rated as class I, 8 as class II, and 62 as class III. Evidence within each area of intervention was synthesized and recommendations for practice standards, practice guidelines, and practice options were made.

CONCLUSIONS

There is substantial evidence to support cognitive-linguistic therapies for people with language deficits after left hemisphere stroke. New evidence supports training for apraxia after left hemisphere stroke. The evidence supports visuospatial rehabilitation for deficits associated with visual neglect after right hemisphere stroke. There is substantial evidence to support cognitive rehabilitation for people with TBI, including strategy training for mild memory impairment, strategy training for postacute attention deficits, and interventions for functional communication deficits. The overall analysis of 47 treatment comparisons, based on class I studies included in the current and previous review, reveals a differential benefit in favor of cognitive rehabilitation in 37 of 47 (78.7%) comparisons, with no comparison demonstrating a benefit in favor of the alternative treatment condition. Future research should move beyond the simple question of whether cognitive rehabilitation is effective, and examine the therapy factors and patient characteristics that optimize the clinical outcomes of cognitive rehabilitation.