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The American Academy of Neurology has reviewed this document and recommends it to Academy membership as an educational tool. This document has been endorsed by the American Academy of Physical Medicine and Rehabilitation, the American Association of Neurological Surgeons, the American Congress of Rehabilitation Medicine, the Brain Injury Association, Inc., and the Child Neurology Society., From the JFK Medical Center (Dr. Giacino), Edison, NJ; Loma Linda University Medical Center (Dr. Ashwal), CA; Brown Schools Rehabilitation Center (Dr. Childs), Austin, TX; Hennepin County Medical Center (Dr. Cranford), Minneapolis, MN; University of Glasgow (Dr. Jennett), United Kingdom; Boston University School of Medicine (Dr. Katz), MA; Chicago Neurological Institute (Dr. Kelly), IL; Southern California Permanente Medical Group (Dr. Rosenberg), San Diego; Moss Rehabilitation Research Institute (Dr. Whyte), MossRehab Hospital, Philadelphia, PA; University of Pittsburgh (Dr. Zafonte), PA; and the Concussion Care Center of Virginia (Dr. Zasler), Glen Allen.
Address correspondence and reprint requests to Dr. Joseph T. Giacino, JFK Johnson Rehabilitation Institute, 2048 Oak Tree Road, Edison, NJ 08820; e-mail: jgiacino{at}solarishs.org
| Article Abstract |
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Background: There is a subgroup of patients with severe alteration in consciousness who do not meet diagnostic criteria for coma or the vegetative state (VS). These patients demonstrate inconsistent but discernible evidence of consciousness. It is important to distinguish patients in MCS from those in coma and VS because preliminary findings suggest that there are meaningful differences in outcome.
Methods: An evidence-based literature review of disorders of consciousness was completed to define MCS, develop diagnostic criteria for entry into MCS, and identify markers for emergence to higher levels of cognitive function.
Results: There were insufficient data to establish evidence-based guidelines for diagnosis, prognosis, and management of MCS. Therefore, a consensus-based case definition with behaviorally referenced diagnostic criteria was formulated to facilitate future empirical investigation.
Conclusions: MCS is characterized by inconsistent but clearly discernible behavioral evidence of consciousness and can be distinguished from coma and VS by documenting the presence of specific behavioral features not found in either of these conditions. Patients may evolve to MCS from coma or VS after acute brain injury. MCS may also result from degenerative or congenital nervous system disorders. This condition is often transient but may also exist as a permanent outcome. Defining MCS should promote further research on its epidemiology, neuropathology, natural history, and management.
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This article, prepared by the Aspen Neurobehavioral Conference Workgroup, proposes diagnostic criteria for MCS.
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Selected members of the workgroup completed independent MEDLINE searches of published articles using the key words coma, vegetative state, minimally responsive state, stupor, slow-to-recover, severe disability, and Glasgow Coma Scale. These terms were then cross-indexed with brain injury, diagnosis, and outcome in eight different permutations to retrieve articles that included patients who did not meet diagnostic criteria for VS, but at the same time, were not considered fully conscious. A total of 260 abstracts containing one or more of the terms were retrieved. Only five reports8,1720 differentiated patients in VS from those with inconsistent signs of consciousness, defined here as MCS. The workgroup concluded that there were insufficient data to establish evidence-based guidelines for diagnosis, prognosis, and management of MCS. Consequently, consensus-based recommendations were developed for the definition of MCS as well as criteria for entry into and emergence from this condition.
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Diagnostic criteria for the minimally conscious state. MCS is distinguished from VS by the presence of behaviors associated with conscious awareness. In MCS, cognitively mediated behavior occurs inconsistently, but is reproducible or sustained long enough to be differentiated from reflexive behavior. The reproducibility of such evidence is affected by the consistency and complexity of the behavioral response. Extended assessment may be required to determine whether a simple response (e.g., a finger movement or eye blink) that is observed infrequently is occurring in response to a specific environmental event (e.g., command to move fingers or blink eyes) or on a coincidental basis. In contrast, a few observations of a complex response (e.g., intelligible verbalization) may be sufficient to determine the presence of consciousness.
To make the diagnosis of MCS, limited but clearly discernible evidence of self or environmental awareness must be demonstrated on a reproducible or sustained basis by one or more of the following behaviors:
Although it is not uncommon for individuals in MCS to demonstrate more than one of the above criteria, in some patients the evidence is limited to only one behavior that is indicative of consciousness. Clinical judgments concerning a patients level of consciousness depend on inferences drawn from observed behavior. Thus, sensory deficits, motor dysfunction, or diminished drive may result in underestimation of cognitive capacity.
Proposed criteria for emergence from the minimally conscious state. Recovery from MCS to higher states of consciousness occurs along a continuum in which the upper boundary is necessarily arbitrary. Consequently, the diagnostic criteria for emergence from MCS are based on broad classes of functionally useful behaviors that are typically observed as such patients recover. Thus, emergence from MCS is characterized by reliable and consistent demonstration of one or both of the following:
Functional interactive communication may occur through verbalization, writing, yes/no signals, or use of augmentative communication devices. Functional use of objects requires that the patient demonstrate behavioral evidence of object discrimination.
To facilitate consistent reporting of findings among clinicians and investigators working with patients in MCS, the following parameters for demonstrating response reliability and consistency should be used:
To help ensure that the operational parameters for demonstrating functional communication and object use described above are equivalent in terms of difficulty, the neurobehavioral profiles of a convenience sample of patients in MCS (n = 24) extracted from a database maintained by one of the authors were reviewed (unpublished data). From this pool, 17 patients were identified who met criteria for either functional object use (FO) or functional communication (FC). The temporal course of recovery of FO and FC was investigated to determine whether the sequence of recovery could serve as an index of difficulty. For example, if most patients met criteria for FO before the criteria for FC were satisfied, it could be concluded that the criteria for FC were more stringent. Data were analyzed for 15 of the 17 available patients. Two patients were excluded because both FO and FC were intact on the admitting examination. Among the remaining 15 patients, seven recovered FO before FC; three recovered FC before FO; and five recovered FO and FC concurrently. The mean time between recovery of FO and FC (independent of sequence) was 8 days (range, 5 to 14 days). Based on these findings, it was concluded that the operational criteria for FO and FC are of equal difficulty.
It is necessary to exclude aphasia, agnosia, apraxia, or sensorimotor impairment as the basis for nonresponsiveness, as opposed to diminished level of consciousness. As noted previously, the criteria for emergence from MCS may underestimate the level of consciousness in some patients. For example, patients with some forms of akinetic mutism demonstrate limited behavioral initiation but are capable of occasional complex cognitively mediated behavior. When there is evidence to suggest that the assessment of level of consciousness is confounded by diminished behavioral initiation, further diagnostic investigation is indicated. Until these diagnostic ambiguities can be resolved by future research, the above definitions should be applied to all patients whose behavior fails to substantiate higher levels of consciousness. It is likely that studies investigating the neurologic substrate underlying subgroups of MCS patients will, in the future, allow the development of diagnostic criteria that are more reliably tied to the level of consciousness.
Recommendations for behavioral assessment of neurocognitive responsiveness. Differential diagnosis among states of impaired consciousness is often difficult. The following steps should be taken to detect conscious awareness and to establish an accurate diagnosis:
Special care must be taken when evaluating infants and children younger than 3 years of age who have sustained severe brain injury. In this age group, assessment of cognitive function is constrained by immature language and motor development. This limits the degree to which command following, verbal expression, and purposeful movement can be relied on to determine whether the diagnostic criteria for MCS have been met.
Prognosis. The natural history and long-term outcome of MCS have not yet been adequately investigated. It is essential to recognize that MCS may occur in a variety of neurologic conditions, such as traumatic brain injury, stroke, progressive degenerative disorders, tumors, neurometabolic diseases, and congenital or developmental disorders. Clinical experience indicates that MCS after an acute injury can exist as a transitional or permanent state. Few studies of the natural history of MCS have been reported.22,26,27 Giacino and Kalmar22 followed 104 patients diagnosed with VS (n = 55) or MCS (n = 49) on admission to rehabilitation during the first 12 months after injury. The diagnosis of MCS was made retrospectively using clinical criteria that approximate the current definition. The MCS group showed more continuous improvement and attained significantly more favorable outcomes on the Disability Rating Scale28 by 1 year than did the VS group. These differences were more pronounced in patients diagnosed with MCS after traumatic brain injury. Fifty percent of patients in the MCS group with traumatic brain injury were found to have none to moderate disability at 12 months, whereas none of the patients in the MCS group without traumatic brain injury were classified in these outcome categories. Although it is not known how many patients will emerge from MCS after 12 months after injury, most patients in MCS for this length of time remain severely disabled according to the Glasgow Outcome Scale.29 As with VS, the likelihood of significant functional improvement diminishes over time.
Consensus-based general approaches to care. There are no existing guidelines regarding the care of patients in MCS. Until sufficient empirical data become available, the following general consensus-based approaches to care are recommended. Evaluation and management decisions will differ depending on the prognosis and the needs of the patient. In all circumstances, the patient should be treated with dignity, and caregivers should be cognizant of the patients potential for understanding and perception of pain. In early MCS, prevention of complications and maintenance of bodily integrity should be emphasized because of the likelihood of further improvement. Efforts should be made to establish functional communication and environmental interaction when possible. A person with experience in neurologic assessment of patients with impaired consciousness should be primarily responsible for establishing the diagnosis and prognosis and for coordinating clinical management. An additional opinion of a physician or other professional with particular expertise in the evaluation, diagnosis, and prognosis of patients in VS and MCS is recommended when the assessment will impact critical management decisions. Such decisions include, but are not limited to, those regarding changes in level of care, disputed treatment decisions, and withdrawal of life-sustaining treatment.
Future directions for research. The care of patients with severe disturbances of consciousness remains a complex challenge partly because of an inadequate foundation of scientific evidence. There are a number of critical areas in which scientific evidence is lacking and additional research is indicated. These areas include:
These recommendations are intended to serve as a reference for clinicians involved in the examination and treatment of patients with severe alterations in consciousness. They are based on the current state of knowledge and are expected to be revised and refined as additional empirical data become available. The primary purpose of these recommendations is to facilitate future scientific investigation and multidisciplinary discussion by providing a common frame of reference for the examination and treatment of patients in MCS.
Appendix Author list with organizational affiliations: Joseph T. Giacino, PhD, American Congress of Rehabilitation Medicine,* Brain Injury Association, Inc.; Stephen Ashwal, MD, Child Neurology Society,* American Academy of Neurology*; Nancy Childs, MD, American Academy of Neurology, American Congress of Rehabilitation Medicine; Ronald Cranford, MD, American Academy of Neurology; Bryan Jennett, CBE, MD, FRCS, International Working Party on the Vegetative State and Profound Brain Damage*; Douglas I. Katz, MD, American Academy of Neurology, American Congress of Rehabilitation Medicine, Brain Injury Association, Inc.; James P. Kelly, MD, American Academy of Neurology, Brain Injury Association; Jay H. Rosenberg, MD, American Academy of Neurology, Brain Injury Association, Inc.; John Whyte, MD, PhD, American Academy of Physical Medicine and Rehabilitation, American Congress of Rehabilitation Medicine, Brain Injury Association, Inc.; Ross Zafonte, DO, American Academy of Physical Medicine and Rehabilitation,* Brain Injury Association, Inc.; Nathan D. Zasler, MD, Brain Injury Association, Inc.,* American Academy of Physical Medicine and Rehabilitation, American Congress of Rehabilitation Medicine. Note: Beverly Walters, MD, Chairperson of the Guidelines Committee of the American Association of Neurological Surgeons, served as the primary reviewer and ex-officio representative of AANS. *Denotes official organizational appointment. Aspen Neurobehavioral Consensus Conference Participants:Christopher M. Filley, MD (conference Co-Chair), University of Colorado Health Sciences Center, Denver, CO; James P. Kelly, MD (conference Co-Chair), Chicago Neurological Institute, Chicago, IL; Joseph T. Giacino, PhD, (workgroup Co-Chair), JFK Medical Center, Edison, NJ; Jay H. Rosenberg, MD (workgroup Co-Chair), Southern California Permanente Medical Group, San Diego, CA; H. Richard Adams, MD, Private Practice, Long Beach, CA; Keith Andrews, MD, Royal Hospital for Neuro-Disability, London, United Kingdom; Stephen Ashwal, MD, Loma Linda University Medical Center, Loma Linda, CA; Nancy Childs, MD, Brown Schools Rehabilitation Center, Austin, TX; Ronald Cranford, MD, Hennepin County Medical Center, Minneapolis, MN; Elie Elovic, MD, Kessler Medical Research and Rehabilitation Center, West Orange, NJ; Candace Gustafson, RN, Brain Injury Association, Inc., Alexandria, VA; Bryan Jennett, CBE, MD, FRCS, University of Glasgow, Glasgow, Scotland; Douglas I. Katz, MD, Boston University School of Medicine, Boston, MA, HealthSouth Braintree Rehabilitation Hospital, Braintree, MA; Theresa Louise-Bender Pape, PhD, CCC-SLP, Hines VAH HSR&D Service/MCHSPR, Maywood, IL; Fred Plum, MD, New York HospitalCornell Medical Center, New York, NY; Nicholas Schiff, MD, New York HospitalCornell Medical Center, New York, NY; Henry Stonnington, MD, 15419 Village Drive, Biloxi, MS; James Tulsky, MD, VA Medical Center, Durham, NC; John Whyte, MD, PhD, MossRehab Hospital, Philadelphia, PA; Jonathan Woodcock, MD, Mediplex RehabDenver, Thorton, CO; Stuart A. Yablon, MD, Mississippi Methodist Rehabilitation Center, Jackson, MS; Ross Zafonte, DO, University of Pittsburgh, Pittsburgh, PA; and Nathan D. Zasler, MD, Concussion Care Center of Virginia, Glen Allen, VA.
| Acknowledgments |
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| Footnotes |
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See also pages 337 and 506
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