fMRI reveals large-scale network activation in minimally conscious patients

BACKGROUND

The minimally conscious state (MCS) resulting from severe brain damage refers to a subset of patients who demonstrate unequivocal, but intermittent, behavioral evidence of awareness of self or their environment. Although clinical examination may suggest residual cognitive function, neurobiological correlates of putative cognition in MCS have not been demonstrated.

OBJECTIVE

To test the hypothesis that MCS patients retain active cerebral networks that underlie cognitive function even though command following and communication abilities are inconsistent.

METHODS

fMRI was employed to investigate cortical responses to passive language and tactile stimulation in two male adults with severe brain injuries leading to MCS and in seven healthy volunteers.

RESULTS

In the case of the patient language-related tasks, auditory stimulation with personalized narratives elicited cortical activity in the superior and middle temporal gyrus. The healthy volunteers imaged during comparable passive language stimulation demonstrated responses similar to the patients' responses. However, when the narratives were presented as a time-reversed signal, and therefore without linguistic content, the MCS patients demonstrated markedly reduced responses as compared with volunteer subjects, suggesting reduced engagement for "linguistically" meaningless stimuli.

CONCLUSIONS

The first fMRI maps of cortical activity associated with language processing and tactile stimulation of patients in the minimally conscious state (MCS) are presented. These findings of active cortical networks that serve language functions suggest that some MCS patients may retain widely distributed cortical systems with potential for cognitive and sensory function despite their inability to follow simple instructions or communicate reliably.

Diagnostic and prognostic guidelines for the vegwive and minimally conscious states

Many individuals who sustain severe brain injury experience prolonged or permanent disorders of consciousness. While these disorders may appear homogeneous, important distinctions exist in prognosis and clinical management. Studies suggest, however, that the incidence of diagnostic inaccuracy is high in both acute care and rehabilitation settings. In this paper, we review consensus-based diagnostic and prognostic criteria for the vegetative and minimally conscious states. We also discuss recent developments and future directions for research in this area.

The JFK Coma Recovery Scale-Revised: measurement characteristics and diagnostic utility

OBJECTIVE

To determine the measurement properties and diagnostic utility of the JFK Coma Recovery Scale-Revised (CRS-R).

DESIGN

Analysis of interrater and test-retest reliability, internal consistency, concurrent validity, and diagnostic accuracy.

SETTING

Acute inpatient brain injury rehabilitation hospital.

PARTICIPANTS

Convenience sample of 80 patients with severe acquired brain injury admitted to an inpatient Coma Intervention Program with a diagnosis of either vegetative state (VS) or minimally conscious state (MCS).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The CRS-R, the JFK Coma Recovery Scale (CRS), and the Disability Rating Scale (DRS).

RESULTS

Interrater and test-retest reliability were high for CRS-R total scores. Subscale analysis showed moderate to high interrater and test-retest agreement although systematic differences in scoring were noted on the visual and oromotor/verbal subscales. CRS-R total scores correlated significantly with total scores on the CRS and DRS indicating acceptable concurrent validity. The CRS-R was able to distinguish 10 patients in an MCS who were otherwise misclassified as in a VS by the DRS.

CONCLUSIONS

The CRS-R can be administered reliably by trained examiners and repeated measurements yield stable estimates of patient status. CRS-R subscale scores demonstrated good agreement across raters and ratings but should be used cautiously because some scores were underrepresented in the current study. The CRS-R appears capable of differentiating patients in an MCS from those in a VS.

The minimally conscious state: defining the borders of consciousness

There is no agreement as to where the limits of consciousness lie, or even if these putative borders exist. Problems inherent to the study of consciousness continue to confound efforts to establish a universally accepted theory of consciousness. Consequently, clinical definitions of consciousness and unconsciousness are unavoidably arbitrary. Recently, a condition of severely altered consciousness has been described, which characterizes the borderzone between the vegetative state and so-called "normal" consciousness. This condition, referred to as the minimally conscious state (MCS), is distinguished from the vegetative state by the presence of minimal but clearly discernible behavioral evidence of self or environmental awareness. This chapter reviews the diagnostic criteria, pathophysiology, prognostic relevance, neurobehavioral assessment procedures and treatment implications associated with MCS.

Rehabilitative management of patients with disorders of consciousness: grand rounds

BACKGROUND

There are no standards of care to guide the selection of rehabilitation assessment and treatment procedures for patients with disorders of consciousness. Recently, consensus-based recommendations for management of patients in the vegetative and minimally conscious states have been developed and disseminated in neurology and neurorehabilitation. This is an important first step toward achieving evidence-based guidelines of care.

OBJECTIVE

Using a "Grand Rounds" format, we illustrate the application of consensus-based diagnostic, prognostic, and treatment recommendations in a patient who sustained severe traumatic brain injury with prolonged alteration in consciousness. After discussing the salient features of the case, we summarize the basic tenets of clinical care for this population.

The vegetative and minimally conscious states: consensus-based criteria for establishing diagnosis and prognosis

Disorders of consciousness continue to be the subject of hot debate in healthcare settings, research consortiums, bioethics departments and media forums. There are no standards of care to guide assessment and treatment decisions resulting in wide disparities in daily practice. In response to this problem, expert panels in neurology and neurorehabilitation were convened and charged with developing consensus-based definitions and diagnostic criteria for disorders of consciousness. The Multi-Society Task Force Report on the persistent vegetative state and the Aspen Workgroup statement on the minimally conscious state represent two such initiatives. This paper summarizes the practice recommendations proposed by these groups and discusses their implications for existing and future interventions.

The minimally conscious state: definition and diagnostic criteria

OBJECTIVE

To establish consensus recommendations among health care specialties for defining and establishing diagnostic criteria for the minimally conscious state (MCS).

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.

Evidence-based cognitive rehabilitation: recommendations for clinical practice

OBJECTIVE

To establish evidence-based recommendations for the clinical practice of cognitive rehabilitation, derived from a methodical review of the scientific literature concerning the effectiveness of cognitive rehabilitation for persons with traumatic brain injury (TBI) or stroke.

DATA SOURCES

A MEDLINE literature search using combinations of these key words as search terms: attention, awareness, cognition, communication, executive, language, memory, perception, problem solving, reasoning, rehabilitation, remediation, and training. Reference lists from identified articles also were reviewed; a total bibliography of 655 published articles was compiled.

STUDY SELECTION

Studies were initially reviewed according to the following exclusion criteria: nonintervention studies; theoretical, descriptive, or review papers; papers without adequate specification of interventions; subjects other than persons with TBI or stroke; pediatric subjects; pharmacologic interventions; and non-English language papers. After screening, 232 articles were eligible for inclusion. After detailed review, 61 of these were excluded as single case reports without data, subjects other than TBI and stroke, and nontreatment studies. This screening yielded 171 articles to be evaluated.

DATA EXTRACTION

Articles were assigned to 1 of 7 categories according to their primary area of intervention: attention, visual perception and constructional abilities, language and communication, memory, problem solving and executive functioning, multi-modal interventions, and comprehensive-holistic cognitive rehabilitation. All articles were independently reviewed by at least 2 committee members and abstracted according to specified criteria. The 171 studies that passed initial review were classified according to the strength of their methods. Class I studies were defined as prospective, randomized controlled trials. Class II studies were defined as prospective cohort studies, retrospective case-control studies, or clinical series with well-designed controls. Class III studies were defined as clinical series without concurrent controls, or studies with appropriate single-subject methodology.

DATA SYNTHESIS

Of the 171 studies evaluated, 29 were rated as Class I, 35 as Class II, and 107 as Class III. The overall evidence within each predefined area of intervention was then synthesized and recommendations were derived based on consideration of the relative strengths of the evidence. The resulting practice parameters were organized into 3 types of recommendations: Practice Standards, Practice Guidelines, and Practice Options.

CONCLUSIONS

Overall, support exists for the effectiveness of several forms of cognitive rehabilitation for persons with stroke and TBI. Specific recommendations can be made for remediation of language and perception after left and right hemisphere stroke, respectively, and for the remediation of attention, memory, functional communication, and executive functioning after TBI. These recommendations may help to establish parameters of effective treatment, which should be of assistance to practicing clinicians.

Multiple fregoli delusions after traumatic brain injury

A 61 year old man after a traumatic brain injury resulting in right frontal and left temporoparietal contusions developed florid Fregoli-type misidentifications. Extensive neuropsychological testing demonstrated significant deficits in executive and memory functions. The patient's neuropsychological profile closely resembled that seen in previously reported patients with Capgras syndrome. Our findings are consistent with the hypothesis that a combination of executive and memory deficits may account for cases of delusional misidentification associated with brain lesions. However, the form which the delusion takes may be influenced by other factors including motivation.

Varieties of deficit unawareness after brain injury

The failure to recognize the existence of disease is known as anosognosia. This article provides a brief discussion of the evolution of this concept and reviews some qualitative differences in the manner in which the disavowal of neurogenic impairment is expressed. Theoretical explanations for the unawareness of deficit after neurologic illness include motivational-symbolic, cognitive subsystem, and supraordinate system theories. Observations from a clinically derived, structured awareness interview are presented, suggesting three factors that may underlie patients' apparent lack of awareness of deficits after traumatic brain injury. These include diminished awareness of deficits secondary to impaired cognition, especially memory and reasoning deficits; psychological reactance and denial of deficits; and a relatively "pure" inability to recognize areas of impaired functioning as a direct consequence of brain injury. The causes of unawareness are likely to be complex and multiply determined in any given patient, although it may be possible to identify primary, secondary, and even tertiary contributions according to specific behavioral and phenomenological characteristics. The ability of patients to modify their perceptions and acknowledgment of deficits after objective feedback may have particular diagnostic value and clinical utility in this regard.

Disorders of consciousness: differential diagnosis and neuropathologic features

Disorders of consciousness present intriguing challenges to the neurologist and neurorehabilitation specialist. Assessment is constrained by the lack of reliable methods of assessing consciousness, and there are no treatment interventions known to influence the course of recovery from these conditions. In addition, the relationship between the clinical features associated with these disorders and their corresponding pathophysiologic substrate is also unclear. Our understanding of disorders of consciousness has not kept pace with the advances in neurosurgical management that have decreased mortality following severe injury. There is still considerable confusion regarding differential diagnosis and prognostication concerning states of severely altered consciousness. The purpose of this article is to discuss the content and neural basis of consciousness and to review the terminology most often used to describe altered states of consciousness. The neurobehavioral criteria for differentiating among specific syndromes associated with severe alterations in consciousness are presented. Representative case studies are utilized to illustrate the characteristic clinical profiles of coma, vegetative state, persistent and permanent vegetative state, minimally conscious state, akinetic mutism, and locked-in syndrome. Areas of ambiguity and controversy are emphasized and future directions for research are suggested.

Monitoring rate of recovery to predict outcome in minimally responsive patients

Existing methods of assessing neurobehavioral responsiveness in severely brain-injured patients are limited by their inability to recognize subtle clinical changes over time. This study evaluates the Coma Recovery Scale (CRS), developed for use during acute rehabilitation. The CRS was designed to detect subtle changes in neurobehavioral status and to predict outcome in patients with sever alterations of consciousness. Acceptable levels of concurrent validity were established with the Disability Rating Scale ([DRS], r = -.93) and the Glasgow Coma Scale ([GCS], r = .90). The CRS was also found to have adequate interrater reliability (kappa = .83). Twenty-eight minimally responsive patients, unable to communicate or follow commands reliably, were evaluated on the CRS, the DRS, and the GCS. Although initial scores on all three scales were significantly correlated with outcome at discharge, change scores were more predictive of outcome. In addition, CRS change scores correlated higher with outcome (r = -.78, p less than .01) than DRS and GCS change scores. These findings indicate that the CRS is a sensitive measure of neurobehavioral responsiveness and suggest that rate of change during acute rehabilitation may be an important outcome predictor.