A Focus on Subtle Signs and Motor Behavior to Unveil Awareness in Unresponsive Brain-Impaired Patients

Abstract

Brain-injured patients in a state of cognitive motor dissociation exhibit a lack of command following using conventional neurobehavioral examination tools but a high level of awareness and language processing when assessed using advanced imaging and electrophysiology techniques. Because of their behavioral unresponsiveness, cognitive motor dissociation patients may seem clinically indistinguishable from those suffering from a “true” disorder of consciousness that affects awareness on a substantial level (coma, vegetative state/unresponsive wakefulness state, or minimally conscious state ‘minus’). Yet, by expanding the range of motor testing across limb, facial and ocular motricity, we may detect subtle, purposeful movements even in the subset of patients classified as vegetative state/unresponsive wakefulness state. We propose the term of clinical cognitive motor dissociation to describe patients showing these slight but determined motor responses and exhibiting a characteristic akinetic motor behavior as opposed to a pyramidal motor system behavior. These patients may harbor hidden cognitive capabilities and significant potential for a good long-term outcome. Indeed, we envision cognitive motor dissociation as ranging from complete (no motor response) to partial (subtle clinical motor response) forms, falling within a spectrum of progressively better motor output in patients with considerable cognitive capabilities. In addition to providing a decisional flowchart, we present this novel approach to classification as a graphical model that illustrates the range of clinical manifestations and recovery trajectories fundamentally differentiating “true” disorders of consciousness from the spectrum of cognitive motor dissociation.

Examining Unresponsive Patients

“…In this issue of Neurology ® , Diserens et al provide a thoughtful exposition of the challenges inherent to the recognition of CMD and remind us of the critical importance of performing a detailed neurologic examination at the bedside. 4 They emphasize the value of using standardized neurobehavioral assessment tools. The most commonly used among such tools, the Coma Recovery Scale-Revised (CRS-R), 5 may be insufficiently sensitive to uncover subtle manifestations of awareness.…”

Reader Response: A Focus on Subtle Signs and Motor Behavior to Unveil Awareness in Unresponsive Brain-Impaired Patients: The Importance of Being Clinical

“…These authors affirmed that the clinical Coma Recovery Scale-Revised frequently fails to identify awareness, referring to a misclassification rate of approximately 30% and therefore proposed to add the Motor Behavior Tool–Revised for neurologic assessment. 2…”

“…Although the authors' proposal is vital to the clinical evaluation of DoC, 2 there are some patients for whom AIEs are necessary. I reported an 8-year-old boy who experienced a near-drowning accident and left in a UWS for 4 years before the study.…”

“…The flow chart proposed by the authors, incorporating those clinical scales, routine MRI, and conventional EEG, 2 is an important tool for clinicians to recognize cases with CMD without AIEs. I also agree with Dr. Rabinstein that in this era of technological medical advances, physicians are at risk of forgetting the basics of “a detailed physical examination combined with a pathophysiologic interpretation of brain MRI and EEG.” 1 This risk affects all medical specialties.…”

Author Response: A Focus on Subtle Signs and Motor Behavior to Unveil Awareness in Unresponsive Brain-Impaired Patients: The Importance of Being Clinical

“…We would like to clarify a few aspects of our approach 1 and thank Prof. Machado for referring to his previously published article. 2 The boy described was probably experiencing a true disorder of consciousness due to his decorticate posturing, suggesting bilateral (sub)cortical destruction with disinhibition of the red nuclei.…”