Persistent vegetative state: report of the American Neurological Association Committee on Ethical Affairs. ANA Committee on Ethical Affairs

Multimodal approaches supporting the diagnosis, prognosis and investigation of neural correlates of disorders of consciousness: A systematic review

The limits of the standard, behaviour-based clinical assessment of patients with disorders of consciousness (DoC) prompted the employment of functional neuroimaging, neurometabolic, neurophysiological and neurostimulation techniques, to detect brain-based covert markers of awareness. However, uni-modal approaches, consisting in employing just one of those techniques, are usually not sufficient to provide an exhaustive exploration of the neural underpinnings of residual awareness. This systematic review aimed at collecting the evidence from studies employing a multimodal approach, that is, combining more instruments to complement DoC diagnosis, prognosis and better investigating their neural correlates. Following the PRISMA guidelines, records from PubMed, EMBASE and Scopus were screened to select peer-review original articles in which a multi-modal approach was used for the assessment of adult patients with a diagnosis of DoC. Ninety-two observational studies and 32 case reports or case series met the inclusion criteria. Results highlighted a diagnostic and prognostic advantage of multi-modal approaches that involve electroencephalography-based (EEG-based) measurements together with neuroimaging or neurometabolic data or with neurostimulation. Multimodal assessment deepened the knowledge on the neural networks underlying consciousness, by showing correlations between the integrity of the default mode network and the different clinical diagnosis of DoC. However, except for studies using transcranial magnetic stimulation combined with electroencephalography, the integration of more than one technique in most of the cases occurs without an a priori-designed multi-modal diagnostic approach. Our review supports the feasibility and underlines the advantages of a multimodal approach for the diagnosis, prognosis and for the investigation of neural correlates of DoCs.

Is oral feeding compatible with an unresponsive wakefulness syndrome?

OBJECTIVE

The aim of the study is to explore the possibility of oral feeding in unresponsive wakefulness syndrome/vegetative state (UWS/VS) patients.

METHOD

We reviewed the clinical information of 68 UWS/VS patients (mean age 45 ± 11; range 16-79 years) searching for mention of oral feeding. UWS/VS diagnosis was made after repeated behavioural assessments using the Coma Recovery Scale-Revised. Patients also had complementary neuroimaging evaluations (positron emission tomography, functional magnetic resonance imaging and electroencephalography and diffusion tensor imaging).

RESULTS

Out of the 68 UWS/VS patients, only two could resume oral feeding (3%). The first patient had oral feeding (only liquid and semi liquid) in addition to gastrostomy feeding and the second one could achieve full oral feeding (liquid and mixed solid food). Clinical assessments concluded that they fulfilled the criteria for a diagnosis of UWS/VS. Results from neuroimaging and neurophysiology were typical for the first patient with regard to the diagnosis of UWS/VS but atypical for the second patient.

CONCLUSION

Oral feeding that implies a full and complex oral phase could probably be considered as a sign of consciousness. However, we actually do not know which components are necessary to consider the swallowing conscious as compared to reflex. We also discussed the importance of swallowing assessment and management in all patients with altered state of consciousness.

The historical origins of the vegetative state: Received wisdom and the utility of the text

The persistent vegetative state (PVS) is one of the most iconic and misunderstood phrases in clinical neuroscience. Coined as a diagnostic category by Scottish neurosurgeon Bryan Jennett and American neurologist Fred Plum in 1972, the phrase "vegetative" first appeared in Aristotle's treatise On the Soul (circa mid-fourth century BCE). Aristotle influenced neuroscientists of the nineteenth and early-twentieth centuries, Xavier Bichat and Walter Timme, and informed their conceptions of the vegetative nervous system. Plum credits Bichat and Timme in his use of the phrase, thus putting the ancient and modern in dialogue. In addition to exploring Aristotle's definition of the "vegetative" in the original Greek, we put Aristotle in conversation with his contemporaries-Plato and the Hippocratics-to better apprehend theories of mind and consciousness in antiquity. Utilizing the discipline of reception studies in classics scholarship, we demonstrate the importance of etymology and historical origin when considering modern medical nosology.

Researching patients in the vegetative state: Difficulties of studying this patient group

It is now generally accepted that all patient groups should benefit from the potential advances in knowledge and understanding that result from clinical research. Despite this principle, patients in the vegetative state remain a group that has been chronically under-researched by neuroscientists because complex ethical questions and logistical dilemmas are raised by such research.

The vegetative state is one of the best known but least understood of neurological conditions. It affects a small but significant number of people who make a poor recovery after sustaining a brain injury and has been brought to public attention through high profile cases in the UK and the USA. This paper defines the vegetative state and explores four important issues that should be considered when planning clinical research in this field. It is demonstrated that not only is it possible to undertake such research but also that there needs to be more of it so that greater numbers of patients and their families will benefit.

Emotional processing of personally familiar faces in the vegetative state

Background

The Vegetative State (VS) is a severe disorder of consciousness in which patients are awake but display no signs of awareness. Yet, recent functional magnetic resonance imaging (fMRI) studies have demonstrated evidence for covert awareness in VS patients by recording specific brain activations during a cognitive task. However, the possible existence of incommunicable subjective emotional experiences in VS patients remains largely unexplored. This study aimed to probe the question of whether VS patients retain a brain ability to selectively process external stimuli according to their emotional value and look for evidence of covert emotional awareness in patients.

Methods and Findings

In order to explore these questions we employed the emotive impact of observing personally familiar faces, known to provoke specific perceptual as well as emotional brain activations. Four VS patients and thirteen healthy controls first underwent an fMRI scan while viewing pictures of non-familiar faces, personally familiar faces and pictures of themselves. In a subsequent imagery task participants were asked to actively imagine one of their parent's faces. Analyses focused on face and familiarity selective regional brain activations and inter-regional functional connectivity. Similar to controls, all patients displayed face selective brain responses with further limbic and cortical activations elicited by familiar faces. In patients as well as controls, Connectivity was observed between emotional, visual and face specific areas, suggesting aware emotional perception. This connectivity was strongest in the two patients who later recovered. Notably, these two patients also displayed selective amygdala activation during familiar face imagery, with one further exhibiting face selective activations, indistinguishable from healthy controls.

Conclusions

Taken together, these results show that selective emotional processing can be elicited in VS patients both by external emotionally salient stimuli and by internal cognitive processes, suggesting the ability for covert emotional awareness of self and the environment in VS patients.

Dissociation of vegetative and minimally conscious patients based on brain operational architectonics: factor of etiology

Discrimination between patients in vegetative (VS) and minimally conscious state (MCS) is currently based upon the behavioral gold standard. Behavioral assessment remains equivocal and difficult to interpret as evidence for the presence or absence of consciousness, resulting in possible clinical misdiagnosis in such patients. Application of an operational architectonics (OA) strategy to electroencephalogram (EEG) analysis reveals that absence of consciousness in patients in VS is paralleled by significant impairment in overall EEG operational architecture compared to patients in MCS: neuronal assemblies become smaller, their life span shortened, and they became highly unstable and functionally disconnected (desynchronized). However, in a previous study, patients with different brain damage etiologies were intermixed. Therefore, the goal of the present study was to investigate whether the application of OA methodology to EEG could reliably dissociate patients in VS and MCS independent of brain damage etiology. We conclude that the observed EEG OA structure impairment in patients in VS and partial preservation in patients in MCS is a marker of consciousness/unconsciousness rather than physiological damage. Results of this study may have neuroscientific, clinical, and ethical implications.

Prognostic Value of Resting-State Electroencephalography Structure in Disentangling Vegetative and Minimally Conscious States

Background. Patients in a vegetative state pose problems in diagnosis, prognosis, and treatment. Currently, no prognostic markers predict the chance of recovery, which has serious consequences, especially in end-of-life decision making. Objective. We aimed to assess an objective measurement of prognosis using advanced electroencephalography (EEG). Methods. EEG data (19 channels) were collected in 14 patients who were diagnosed to be persistently vegetative based on repeated clinical evaluations at 3 months following brain damage. EEG structure parameters (amplitude, duration, and variability within quasi-stationary segments, as well as the spatial synchrony between such segments and the strength of this synchrony) were used to predict recovery of consciousness 3 months later. Results. The number and strength of cortical functional connections between EEG segments were higher in patients who recovered consciousness ( P < .05 to P < .001) compared with those who did not recover. Linear regression analysis confirms that EEG structure parameters are capable of predicting ( P = .0025) recovery of consciousness 6 months postinjury, whereas the same analysis failed to significantly predict patient outcome based on aspects of their clinical history alone ( P = .629) or conventional EEG spectrum power ( P = .473). Conclusions. The result of this preliminary study demonstrates that structural strategy of EEG analysis is better suited for providing prognosis of consciousness recovery than existing methods of clinical assessment and of conventional EEG. Our results may be a starting point for developing reliable prognosticators in patients who are in a vegetative state, with the potential to improve their day-to-day management, quality of life, and access to early interventions.

The value of spontaneous EEG oscillations in distinguishing patients in vegetative and minimally conscious states

OBJECTIVE

The value of spontaneous electroencephalography (EEG) oscillations in distinguishing patients in vegetative state (VS) and minimally conscious states (MCS) was studied.

METHODS

We quantified dynamic repertoire of EEG oscillations in resting condition with closed eyes in patients in VS and MCS. The exact composition of EEG oscillations was assessed by the probability-classification analysis of short-term EEG spectral patterns.

RESULTS

The probability of delta, theta, and slow-alpha oscillations occurrence was smaller for patients in MCS than for VS. Additionally, only patients in MCS demonstrated fast-alpha oscillation occurrence. Depending on the type and composition of EEG oscillations, the probability of their occurrence was either etiology dependent or independent. The probability of EEG oscillations occurrence differentiated brain injuries with different etiologies.

CONCLUSIONS

Spontaneous EEG oscillations have a potential value in distinguishing patients in VS and MCS.

SIGNIFICANCE

This work may have implications for clinical care, rehabilitative programs, and medical-legal decisions in patients with impaired consciousness states following coma due to acute brain injuries.

HIGHLIGHTS

The probability of delta, theta, and slow-alpha oscillations occurrence was smaller and the probability of fast-alpha oscillations occurrence was higher for patients in MCS than for patients in VS. The probability of EEG oscillations occurrence differentiated brain injuries with different etiologies. Spontaneous EEG has a potential value in distinguishing patients in VS and MCS.

DMN Operational Synchrony Relates to Self-Consciousness: Evidence from Patients in Vegetative and Minimally Conscious States

The default mode network (DMN) has been consistently activated across a wide variety of self-related tasks, leading to a proposal of the DMN’s role in self-related processing. Indeed, there is limited fMRI evidence that the functional connectivity within the DMN may underlie a phenomenon referred to as self-awareness. At the same time, none of the known studies have explicitly investigated neuronal functional interactions among brain areas that comprise the DMN as a function of self-consciousness loss. To fill this gap, EEG operational synchrony analysis [1, 2] was performed in patients with severe brain injuries in vegetative and minimally conscious states to study the strength of DMN operational synchrony as a function of self-consciousness expression. We demonstrated that the strength of DMN EEG operational synchrony was smallest or even absent in patients in vegetative state, intermediate in patients in minimally conscious state and highest in healthy fully self-conscious subjects. At the same time the process of ecoupling of operations performed by neuronal assemblies that comprise the DMN was highest in patients in vegetative state, intermediate in patients in minimally conscious state and minimal in healthy fully self-conscious subjects. The DMN’s frontal EEG operational module had the strongest decrease in operational synchrony strength as a function of selfconsciousness loss, when compared with the DMN’s posterior modules. Based on these results it is suggested that the strength of DMN functional connectivity could mediate the strength of self-consciousness expression. The observed alterations similarly occurred across EEG alpha, beta1 and beta2 frequency oscillations. Presented results suggest that the EEG operational synchrony within DMN may provide an objective and accurate measure for the assessment of signs of self-(un)consciousness in these challenging patient populations. This method therefore, may complement the current diagnostic procedures for patients with severe brain injuries and, hence, the planning of a rational rehabilitation intervention.

Life or death: prognostic value of a resting EEG with regards to survival in patients in vegetative and minimally conscious States

OBJECTIVE

To investigate the potentially prognostic value of a resting state electroencephalogram (EEG) with regards to the clinical outcome from vegetative and minimally conscious states (VS and MCS) in terms of survival six months after a brain injury.

METHODS

We quantified a dynamic repertoire of EEG oscillations in resting condition with eyes closed in patients in VS and MCS. The exact composition of EEG oscillations was assessed by analysing the probability-classification of short-term EEG spectral patterns.

RESULTS

Results demonstrated that (a) the diversity and the variability of EEG for Non-Survivors were significantly lower than for Survivors; and (b) a higher probability of mostly delta and slow-theta oscillations occurring either alone or in combination were found during the first assessment for patients with a bad outcome (i.e., those who died) within six months of an injury compared to patients who survived. At the same time, patients with a good outcome (i.e., those who survived) after six months post-injury had a higher probability of mostly fast-theta and alpha oscillations occurring either alone or in combination during the first assessment when compared to patients who died within six months of an injury.

CONCLUSIONS

Resting state EEGs properly analysed may have a potentially prognostic value with regards to the outcome from VS or MCS in terms of survival six months after a brain injury.

SIGNIFICANCE

This work may have implications for clinical care, rehabilitative programmes and medical-legal decisions for patients with impaired consciousness states after being in a coma due to acute brain injuries.

"Relevance vector machine" consciousness classifier applied to cerebral metabolism of vegetative and locked-in patients

The vegetative state is a devastating condition where patients awaken from their coma (i.e., open their eyes) but fail to show any behavioural sign of conscious awareness. Locked-in syndrome patients also awaken from their coma and are unable to show any motor response to command (except for small eye movements or blinks) but recover full conscious awareness of self and environment. Bedside evaluation of residual cognitive function in coma survivors often is difficult because motor responses may be very limited or inconsistent. We here aimed to disentangle vegetative from "locked-in" patients by an automatic procedure based on machine learning using fluorodeoxyglucose PET data obtained in 37 healthy controls and in 13 patients in a vegetative state. Next, the trained machine was tested on brain scans obtained in 8 patients with locked-in syndrome. We used a sparse probabilistic Bayesian learning framework called "relevance vector machine" (RVM) to classify the scans. The trained RVM classifier, applied on an input scan, returns a probability value (p-value) of being in one class or the other, here being "conscious" or not. Training on the control and vegetative state groups was assessed with a leave-one-out cross-validation procedure, leading to 100% classification accuracy. When applied on the locked-in patients, all scans were classified as "conscious" with a mean p-value of .95 (min .85). In conclusion, even with this relatively limited data set, we could train a classifier distinguishing between normal consciousness (i.e., wakeful conscious awareness) and the vegetative state (i.e., wakeful unawareness). Cross-validation also indicated that the clinical classification and the one predicted by the automatic RVM classifier were in accordance. Moreover, when applied on a third group of "locked-in" consciously aware patients, they all had a strong probability of being similar to the normal controls, as expected. Therefore, RVM classification of cerebral metabolic images obtained in coma survivors could become a useful tool for the automated PET-based diagnosis of altered states of consciousness.

Care protocol for persistent vegetative states (PVS) and minimally conscious state (MSC) in Lorraine: retrospective study over an 18-year period

OBJECTIVES

Retrospective analysis of the efficiency of a protocol for care of chronic vegetative states (CVS) and minimally conscious state (MCS) in Lorraine.

MATERIAL AND METHOD

Two indicators are used: protocol activity (number of patients hospitalized between 1988 and 2006, number of admissions per year, of requests per year, origin of requests, waiting time) and the epidemiological data (age, sex ratio, etiology, length of stay, geographic origin, number of deaths, number of hospital discharges). The number of CVS and MCS and patients having progressed towards arousal is specified as well as the technical procedures (orthopedic surgery, number of tracheotomies).

RESULTS

Forty-seven patients (30 males and 17 females) were hospitalized in a 12-bed unit. The number of admissions per year was 2.4, and the annual number of requests varied between five and 15. Hospitalization times ranged from six to 18 months. The average length of hospitalization was 41 months. Eighty-eight percent of the cases were residents of Lorraine. The etiology was traumatic (53%), vascular (38% including 12% anoxia), miscellaneous (9%). Fifteen percent rate of return to arousal (average time period: 28.41 months, traumatic etiology) with hospital discharge in four cases.

CONCLUSION

The protocol is managed as part of a local scheme and enables an appropriate response to a specific clinical profile by providing up-to-date multidiscipline follow-up care and a rapid solution should intercurrent events occur (signs of arousal, orthopedic deterioration, change of environment). Typical limitations are geographical remoteness and difficulties with family support care.

Quality-of-life considerations in substitute decision-making for severely disabled neonates: the problem of developing awareness

Substitute decision-makers for severely disabled neonates who can be kept alive but who will require constant medical interventions and will die at the latest in their teens are faced with a difficult decision when trying to decide whether to keep the infant alive. By and large, the primary focus of their decision-making centers on what is in the best interests of the newborn. The best-interests criterion, in turn, is importantly conditioned by quality-of-life considerations. However, the concept of quality of life is logically and ethically different for patients with a developing as opposed to a developed awareness. Unfortunately, this difference is ignored by current quality-of-life considerations, there are no quality-of-life measures that take this difference into account, and decision-making proceeds entirely without acknowledging this fact. This note outlines why this is a problem and why there is a need for a new set of tools that incorporates this distinction if the substitute decision-makers are to apply the best-interest criterion in a meaningful way.

Self-consciousness in non-communicative patients

The clinical and para-clinical examination of residual self-consciousness in non-communicative severely brain damaged patients (i.e., coma, vegetative state and minimally conscious state) remains exceptionally challenging. Passive presentation of the patient's own name and own face are known to be effective attention-grabbing stimuli when clinically assessing consciousness at the patient's bedside. Event-related potential and functional neuroimaging studies using such self-referential stimuli are currently being used to disentangle the cognitive hierarchy of self-processing. We here review neuropsychological, neuropathological, electrophysiological and neuroimaging studies using the own name and own face paradigm obtained in conscious waking, sleep, pharmacological coma, pathological coma and related disorders of consciousness. Based on these results we discuss what we currently do and do not know about the functional significance of the neural network involved in "automatic" and "conscious" self-referential processing.

Guidelines for Quality Management of Apallic Syndrome / Vegetative State

INTRODUCTION

Epidemiology in Europe shows constantly increasing figures for the apallic syndrome (AS)/vegetative state (VS) as a consequence of advanced rescue, emergency services, intensive care treatment after acute brain damage and high-standard activating home nursing for completely dependent end-stage cases secondary to progressive neurological disease. Management of patients in irreversible permanent AS/VS has been the subject of sustained scientific and moral-legal debate over the past decade.

METHODS

A task force on guidelines for quality management of AS/VS was set up under the auspices of the Scientific Panel Neurotraumatology of the European Federation of Neurological Societies to address key issues relating to AS/VS prevalence and quality management. Collection and analysis of scientific data on class II (III) evidence from the literature and recommendations based on the best practice as resulting from the task force members' expertise are in accordance with EFNS Guidance regulations.

FINDINGS

The overall incidence of new AS/VS full stage cases all etiology is 0.5-2/100.000 population per year. About one third are traumatic and two thirds non traumatic cases. Increasing figures for hypoxic brain damage and progressive neurological disease have been noticed. The main conceptual criticism is based on the assessment and diagnosis of all different AS/VS stages based solely on behavioural findings without knowing the exact or uniform pathogenesis or neuropathological findings and the uncertainty of clinical assessment due to varying inclusion criteria. No special diagnostics, no specific medical management can be recommended for class II or III AS treatment and rehabilitation. This is why sine qua non diagnostics of the clinical features and appropriate treatment of AS/VS patients of "AS full, remission, defect and end stages" require further professional training and expertise for doctors and rehabilitation personnel.

INTERPRETATION

Management of AS aims at the social reintegration of patients or has to guarantee humanistic active nursing if treatment fails. Outcome depends on the cause and duration of AS/VS as well as patient's age. There is no single AS/VS specific laboratory investigation, no specific regimen or stimulating intervention to be recommended for improving higher cerebral functioning. Quality management requires at least 3 years of advanced training and permanent education to gain approval of qualification for AS/VS treatment and expertise. Sine qua non areas covering AS/VS institutions for early and long-term rehabilitation are required on a population base (prevalence of 2/100.000/year) to quicken functional restoration and to prevent or treat complications. Caring homes are needed for respectful humane nursing including basal sensor-motor stimulating techniques. Passive euthanasia is considered an act of mercy by physicians in terms of withholding treatment; however, ethical and legal issues with regard to withdrawal of nutrition and hydration and end of life discussions raise deep concerns. The aim of the guideline is to provide management guidance (on the best medical evidence class II and III or task force expertise) for neurologists, neurosurgeons, other physicians working with AS/VS patients, neurorehabilitation personnel, patients, next-of-kin, and health authorities.

The declaration of death and the withdrawal of care in the neurologic patient

Intensive care technologies have led to an increase in patients who are neurologically devastated and deceased. The practical, moral, and ethical situations encountered can be varied and challenging to manage. Decisions and discussions surrounding withdrawal of care, death by neurologic criteria, and organ donation require significant knowledge of the prognosis, ancillary testing, and definitions of these processes. Experience and skill are often required on the part of physicians and staff to guide families through these most difficult of circumstances.

Chronic disorders of consciousness

The vegetative state and the minimally conscious state are disorders of consciousness that can be acute and reversible or chronic and irreversible. Diffuse lesions of the thalami, cortical neurons, or the white-matter tracts that connect them cause the vegetative state, which is wakefulness without awareness. Functional imaging with PET and functional MRI shows activation of primary cortical areas with stimulation, but not of secondary areas or distributed neural networks that would indicate awareness. Vegetative state has a poor prognosis for recovery of awareness when present for more than a year in traumatic cases and for 3 months in non-traumatic cases. Patients in minimally conscious state are poorly responsive to stimuli, but show intermittent awareness behaviours. Indeed, findings of preliminary functional imaging studies suggest that some patients could have substantially intact awareness. The outcomes of minimally conscious state are variable. Stimulation treatments have been disappointing in vegetative state but occasionally improve minimally conscious state. Treatment decisions for patients in vegetative state or minimally conscious state should follow established ethical and legal principles and accepted practice guidelines of professional medical specialty societies.

The vegetative state and the Royal College of Physicians guidance

The Royal College of Physicians of the UK, together with the Colleges of Edinburgh and Glasgow, have produced guidance on the diagnosis and management of people in the vegetative state (report of a working party of the Royal College of Physicians, 2003). Such guidance is important when the single criterion for awareness in an individual is the perception of that awareness by a potentially fallible observer. The current guidance is reviewed and comparisons made with existing arrangements in other countries. Consideration is given to the possibility of future improvements in diagnosis with the advent of imaging and metabolic assessments of brain function and the need to define the required qualifications and training for those "experts" who are currently involved in the diagnosis of the vegetative state.

Science and society: death, unconsciousness and the brain

The concept of death has evolved as technology has progressed. This has forced medicine and society to redefine its ancient cardiorespiratory centred diagnosis to a neurocentric diagnosis of death. The apparent consensus about the definition of death has not yet appeased all controversy. Ethical, moral and religious concerns continue to surface and include a prevailing malaise about possible expansions of the definition of death to encompass the vegetative state or about the feared bias of formulating criteria so as to facilitate organ transplantation.

Cerebral processing of auditory and noxious stimuli in severely brain injured patients: Differences between VS and MCS

We review cerebral processing of auditory and noxious stimuli in minimally conscious state (MCS) and vegetative state (VS) patients. In contrast with limited brain activation found in VS patients, MCS patients show activation similar to controls in response to auditory, emotional and noxious stimuli. Despite an apparent clinical similarity between MCS and VS patients, functional imaging data show striking differences in cortical segregation and integration between these two conditions. However, in the absence of a generally accepted neural correlate of consciousness as measured by functional neuroimaging, clinical assessment remains the gold standard for the evaluation and management of severely brain damaged patients.

Zerebrale Funktionen bei hirngeschädigten Patienten

Comatose, vegetative, minimally conscious or locked-in patients represent a problem in terms of diagnosis, prognosis, treatment and everyday management at the intensive care unit. The evaluation of possible cognitive functions in these patients is difficult because voluntary movements may be very small, inconsistent and easily exhausted. Functional neuroimaging cannot replace the clinical assessment of patients with altered states of consciousness. Nevertheless, it can describe objectively how deviant from normal the cerebral activity is and its regional distribution at rest and under various conditions of stimulation. The quantification of brain activity differentiates patients who sometimes only differ by a brief and incomplete blink of an eye. In the present paper, we will first try to define consciousness as it can be assessed at the patient's bedside. We then review the major clinical entities of altered states of consciousness encountered in the intensive care unit. Finally, we discuss the functional neuroanatomy of these conditions as assessed by positron emission tomography (PET) scanning.

Brain function in coma, vegetative state, and related disorders

We review the nosological criteria and functional neuroanatomical basis for brain death, coma, vegetative state, minimally conscious state, and the locked-in state. Functional neuroimaging is providing new insights into cerebral activity in patients with severe brain damage. Measurements of cerebral metabolism and brain activations in response to sensory stimuli with PET, fMRI, and electrophysiological methods can provide information on the presence, degree, and location of any residual brain function. However, use of these techniques in people with severe brain damage is methodologically complex and needs careful quantitative analysis and interpretation. In addition, ethical frameworks to guide research in these patients must be further developed. At present, clinical examinations identify nosological distinctions needed for accurate diagnosis and prognosis. Neuroimaging techniques remain important tools for clinical research that will extend our understanding of the underlying mechanisms of these disorders.

Acetazolamide vasoreactivity in persistent vegetative state and vascular dementia evaluated by transcranial harmonic perfusion imaging and Doppler sonography

To clarify the pathophysiological differences of the cerebrovascular reserve capacity in relation to cerebral cognitive impairments between persistent vegetative state (PVS) and vascular dementia (VD), we evaluated acetazolamide (ACZ) vasoreactivity testing by transcranial harmonic perfusion imaging (HPI) and Doppler sonography (TCD).

METHODS

The subjects were 11 adult patients with severe cognitive impairments (4 PVS, 7 VD). TCD mean velocity (Vm) in the middle and posterior cerebral artery (MCA, PCA) and peak intensity (PI), area under curve (AUC), and mean transit time (MTT) analyzed by HPI time-intensity curves in the bilateral temporal lobe (TL), basal ganglia (BG), and thalamus (Th) were evaluated before and after ACZ administration. Resting values and relative changes (%delta) of TCD and HPI parameters were compared between PVS and VD.

RESULTS

a) Resting values: There were no significant differences between the two groups. b) Vasoreactivity: 1) PVS: %delta Vm decreased in the left PCA and MCA. %delta PI/AUC/MTT decreased in the left TL and bilateral BG. 2) VD: %delta PI/AUC decreased in the right TL. %delta MTT tended to decrease in the right side.

CONCLUSION

ACZ vasoreactivity tests by transcranial HPI and TCD allowed bedside, non-invasive, quantitative evaluation of the pathophysiology of cognitive function impairment and treatments, in relation to cerebrovascular reserve capacity in PVS and VD.

Cortical processing of noxious somatosensory stimuli in the persistent vegetative state

The persistent vegetative state (PVS) is a devastating medical condition characterized by preserved wakefulness contrasting with absent voluntary interaction with the environment. We used positron emission tomography to assess the central processing of noxious somatosensory stimuli in the PVS. Changes in regional cerebral blood flow were measured during high-intensity electrical stimulation of the median nerve compared with rest in 15 nonsedated patients and in 15 healthy controls. Evoked potentials were recorded simultaneously. The stimuli were experienced as highly unpleasant to painful in controls. Brain glucose metabolism was also studied with [(18)F]fluorodeoxyglucose in resting conditions. In PVS patients, overall cerebral metabolism was 40% of normal values. Nevertheless, noxious somatosensory stimulation-activated midbrain, contralateral thalamus, and primary somatosensory cortex in each and every PVS patient, even in the absence of detectable cortical evoked potentials. Secondary somatosensory, bilateral insular, posterior parietal, and anterior cingulate cortices did not show activation in any patient. Moreover, in PVS patients, the activated primary somatosensory cortex was functionally disconnected from secondary somatosensory, bilateral posterior parietal, premotor, polysensory superior temporal, and prefrontal cortices. In conclusion, somatosensory stimulation of PVS patients, at intensities that elicited pain in controls, resulted in increased neuronal activity in primary somatosensory cortex, even if resting brain metabolism was severely impaired. However, this activation of primary cortex seems to be isolated and dissociated from higher-order associative cortices.

Positive outcomes in traumatic brain injury-vegetative state: patients treated with bromocriptine

OBJECTIVE

To assess the effects of multidisciplinary rehabilitation interventions and use of bromocriptine on outcome in patients with traumatic brain injury-vegetative state (TBI-VS).

DESIGN

Retrospective review of clinical cases.

SETTING

Free-standing rehabilitation hospital; Acute and extended rehabilitation hospital.

PARTICIPANTS

Five consecutive TBI-VS patients, as well as 33 TBI-VS patients and 37 traumatic brain injury-minimally conscious state (TBI-MCS) patients reported in the literature.

INTERVENTIONS

Bromocriptine administration, systematic neuropsychologic testing, sensory stimulation, and traditional comprehensive rehabilitation with physical therapy, occupational therapy, and speech therapy.

MAIN OUTCOME MEASURES

Disability Rating Scale (DRS) at 1, 3, 6, and 12 months postinjury and FIM instrument scores at 1 month and 12 months postinjury, Coma Recovery Scale, and Barry Rehabilitation Inpatient Screening of Cognition.

RESULTS

The 5 TBI-VS patients emerged from a VS into a MCS and regained functional status. Their recovery of physical and cognitive functioning, as rated by the DRS, was greater than previously reported in the literature for patients in a VS or MCS at 3, 6, and 12 months postinjury.

CONCLUSION

Bromocriptine administration, systematic neuropsychologic testing, sensory stimulation, a comprehensive rehabilitation program, or a combination of these treatments may enhance functional recovery in this TBI-VS patient group. Further systematic study to quantify the contribution of these variables and to reproduce this data in a larger patient population should be performed.

Coma prognosis in children. Part I: definitional and methodological challenges

Prediction of outcome from coma is a frequent and important task of neurologists. It is difficult enough in adult patients and even more difficult in children. Part I of this review considers some of the methodological problems and caveats besetting clinical research in this field: the very definition of coma, definition of the study population and outcome variables, study design, the fallacy of self-fulfilling prophecy, early death rate from nonneurologic causes resulting in low statistical power, and invalid attempts to compensate for that by combining outcome categories, lumping together age groups, short and inhomogeneous follow-up, and failure to provide confidence intervals. Part II reviews the clinical pediatric coma-prognosis literature, first according to etiology and then according to electrodiagnostic tests.

Impaired effective cortical connectivity in vegetative state: preliminary investigation using PET

Vegetative state (VS) is a condition of abolished awareness with persistence of arousal. Awareness is part of consciousness, which itself is thought to represent an emergent property of cerebral neural networks. Our hypothesis was that part of the neural correlate underlying VS is an altered connectivity, especially between the associative cortices. We assessed regional cerebral glucose metabolism (rCMRGlu) and effective cortical connectivity in four patients in VS by means of statistical parametric mapping and [18F]fluorodeoxyglucose-positron emission tomography. Our data showed a common pattern of impaired rCMRGlu in the prefrontal, premotor, and parietotemporal association areas and posterior cingulate cortex/precuneus in VS. In a next step, we demonstrated that in VS patients various prefrontal and premotor areas have in common that they are less tightly connected with the posterior cingulate cortex than in normal controls. These results provide a strong argument for an alteration of cortical connectivity in VS patients.

What happens after brain injury?

Traumatic brain injury is one of the leading causes of injury and death among the young in the United States. Severity can range from the brief confusion of a football player who has had his "bell rung" to the complete loss of voluntary behavior seen in the vegetative state. In this article, Dr Goldberg reviews the rehabilitation process used to restore the fullest function possible within the limits of the patient's injury, with emphasis on innovative assessment and treatment techniques. He also describes an approach to evaluation of minimally conscious patients that can be used to detect and confirm the presence of active cognition.

Persistent vegetative state: clinical and ethical issues

Coma, vegetative state, lock-in syndrome and akinetic mutism are defined. Vegetative state is a state with no evidence of awareness of self or environment and showing cycles of sleep and wakefulness. PVS is an operational definition including time as a variable. PVS is a vegetative state that has endured or continued for at least one month. PVS can be diagnosed with a reasonable amount of medical certainty; however, the diagnosis of PVS must be kept separate from the outcome. The patient outcome can be predicted based on etiology and age. Using outcome probabilities and etiology as criteria, patients can be subdivided in 5 groups and reasonable management guidelines can be suggested. Three levels of care can be provided to PVS patients: high technology, supportive and compassionate care. Pragmatic options for the various subgroups of patients are suggested. Management decisions will remain difficult for both the family and the health-care team. The role of the physician in these difficult cases is to share the decision-making with the family.

Specific changes in human brain after hypoglycemic injury

BACKGROUND AND PURPOSE

Very few reports are available on serial changes in the human brain after severe hypoglycemic injury. The aim of this study was to investigate sequential neuroradiological changes in brains of patients after hypoglycemic coma compared with those after cardiac arrest previously studied with the same methods.

METHODS

We repeatedly studied CT scans and MR images obtained at 1.5 T in four vegetative patients after profound hypoglycemia associated with diabetes mellitus.

RESULTS

In all patients, consecutive CT scans showed symmetrical, persistent low-density lesions with transient enhancement in the caudate and lenticular nuclei and transient enhancement in the cerebral cortex 7 to 14 days after onset. Serial MR images consistently revealed symmetrical lesions of persistent hyperintensity and hypointensity on T1- and T2-weighted images, respectively, in the caudate and lenticular nuclei, cerebral cortex, substantia nigra, and/or hippocampus from 8 days to 12 months after onset.

CONCLUSIONS

Repeated MR images revealed specific lesions in the bilateral basal ganglia, cerebral cortex, substantia nigra, and hippocampus, which suggests the particular vulnerability of these areas to hypoglycemia in the human brain. We speculate that the localized lesions represent tissue degeneration, including some combination of selective neuronal death, proliferation of astrocytic glial cells, paramagnetic substance deposition, and/or lipid accumulation. The absence of localized hemorrhages on MR images in hypoglycemic encephalopathy is in marked contrast to the presence of regional minor hemorrhages in postischemic-anoxic encephalopathy.

Recommendations for use of uniform nomenclature pertinent to patients with severe alterations in consciousness. American Congress of Rehabilitation Medicine

There continues to be considerable confusion and controversy on the use of diagnostic and clinical terms assigned to patients with severe alterations in consciousness. This confusion results largely from the lack of a uniform classification system that is based on behaviorally defined criteria. This position paper provides recommendations for defining coma, vegetative state (including persistent and permanent vegetative state), akinetic mutism, the minimally responsive state, and locked-in syndrome based on neurobehavioral and neuropathologic features. Current controversies surrounding use of these terms also are discussed.

Specific changes in human brain following reperfusion after cardiac arrest

BACKGROUND AND PURPOSE

Very few reports are available on serial changes in human brain after cardiac arrest. The primary objective of this study is to investigate sequential neuroradiological changes in patients remaining in a persistent vegetative state following resuscitation after cardiac arrest.

METHODS

We repeatedly studied eight vegetative patients resuscitated from unexpected out-of-hospital cardiac arrest using computed tomographic (CT) scanning and high-field magnetic resonance (MR) imaging at 1.5 T.

RESULTS

In seven of the eight patients, CT scans obtained between days 2 and 6 features symmetrical low-density lesions in the bilateral caudate, lenticular, and/or thalamic nuclei. These ischemic lesions were persistently of low density on serial CT scans. In these seven patients, MR images demonstrated what were thought to be hemoglobin degradation products derived from minor hemorrhages localized in the bilateral basal ganglia, thalami, and/or substantia nigra. Diffuse brain edema in the acute stage and diffuse brain atrophy in the chronic stage were consistent neuroradiological findings. No abnormal enhanced lesions were demonstrated by CT scans.

CONCLUSIONS

The most characteristic findings on high-field MR images were symmetrical lesions in the bilateral basal ganglia, thalami, and/or substantia nigra with specific changes suggestive of minor hemorrhages that were not evident on CT scans. We speculate that these minor hemorrhages result from diapedesis of red blood cells in these regions during the reperfusion period through the endothelium disrupted by ischemia-reperfusion insult.

Medical aspects of the persistent vegetative state (1)

This consensus statement of the Multi-Society Task Force summarizes current knowledge of the medical aspects of the persistent vegetative state in adults and children. The vegetative state is a clinical condition of complete unawareness of the self and the environment, accompanied by sleep-wake cycles, with either complete or partial preservation of hypothalamic and brain-stem autonomic functions. In addition, patients in a vegetative state show no evidence of sustained, reproducible, purposeful, or voluntary behavioral responses to visual, auditory, tactile, or noxious stimuli; show no evidence of language comprehension or expression; have bowel and bladder incontinence; and have variably preserved cranial-nerve and spinal reflexes. We define persistent vegetative state as a vegetative state present one month after acute traumatic or nontraumatic brain injury or lasting for at least one month in patients with degenerative or metabolic disorders or developmental malformations. The clinical course and outcome of a persistent vegetative state depend on its cause. Three categories of disorder can cause such a state: acute traumatic and non-traumatic brain injuries; degenerative and metabolic brain disorders, and severe congenital malformations of the nervous system. Recovery of consciousness from a posttraumatic persistent vegetative state is unlikely after 12 months in adults and children. Recovery from a nontraumatic persistent vegetative state after three months is exceedingly rare in both adults and children. Patients with degenerative or metabolic disorders or congenital malformations who remain in a persistent vegetative state for several months are unlikely to recover consciousness. The life span of adults and children in such a state is substantially reduced. For most such patients, life expectancy ranges from 2 to 5 years; survival beyond 10 years is unusual.