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

Abstract

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.

From unresponsive wakefulness to minimally conscious PLUS and functional locked-in syndromes: recent advances in our understanding of disorders of consciousness

“…In the presence of increasingly hard neurophysiologic markers of consciousness [17], the burden of proof for establishing consciousness in severely brain damaged patients no longer exclusively lies in behavioural assessment [67]. Clearly, patients who can ''play tennis'' and ''imagine walking in their house'' or use these complex mental imagery tasks to accurately communicate, cannot be considered vegetative/unresponsive or minimally conscious.…”

The auditory P300-based single-switch brain–computer interface: Paradigm transition from healthy subjects to minimally conscious patients

“…MCS is a disorder of consciousness (DOC) that is clinically identi-fied on the basis of behavioral assessment that shows the presence of non-reflexive responses to visual and auditory stimulation [11,12]. Severe motor impairment might, however, prevent the disclosure of awareness even during a careful repeated examination, leading to a rate of misdiagnosis of approximately 40 % [10].…”

Prevalence of persistent vegetative state in patients with severe traumatic brain injury and its trend during the past four decades: A meta-analysis

“…First, the included articles were observational studies, which have potential risk of biases and none of them complying all AHRQ items related to risk of bias. Second, the limitations of behavioral assessment techniques for the diagnosis of VS influence the accuracy of the PVS prevalence reported in the included studies (Giacino et al, 2009). A diagnostic criterion for MCS did not exist until 2002, which may make the prevalence reported in studies before 2002 higher the actual prevalence.…”