Cognitive Motor Dissociation in Disorders of Consciousness

Abstract

Background: Patients with brain injury who are unresponsive to commands may perform cognitive tasks that are detected on functional magnetic resonance imaging (fMRI) and electroencephalography (EEG). This phenomenon, known as cognitive motor dissociation, has not been systematically studied in a large cohort of persons with disorders of consciousness.

Methods: In this prospective cohort study conducted at six international centers, we collected clinical, behavioral, and task-based fMRI and EEG data from a convenience sample of 353 adults with disorders of consciousness. We assessed the response to commands on task-based fMRI or EEG in participants without an observable response to verbal commands (i.e., those with a behavioral diagnosis of coma, vegetative state, or minimally conscious state-minus) and in participants with an observable response to verbal commands. The presence or absence of an observable response to commands was assessed with the use of the Coma Recovery Scale-Revised (CRS-R).

Results: Data from fMRI only or EEG only were available for 65% of the participants, and data from both fMRI and EEG were available for 35%. The median age of the participants was 37.9 years, the median time between brain injury and assessment with the CRS-R was 7.9 months (25% of the participants were assessed with the CRS-R within 28 days after injury), and brain trauma was an etiologic factor in 50%. We detected cognitive motor dissociation in 60 of the 241 participants (25%) without an observable response to commands, of whom 11 had been assessed with the use of fMRI only, 13 with the use of EEG only, and 36 with the use of both techniques. Cognitive motor dissociation was associated with younger age, longer time since injury, and brain trauma as an etiologic factor. In contrast, responses on task-based fMRI or EEG occurred in 43 of 112 participants (38%) with an observable response to verbal commands.

Conclusions: Approximately one in four participants without an observable response to commands performed a cognitive task on fMRI or EEG as compared with one in three participants with an observable response to commands. (Funded by the James S. McDonnell Foundation and others.).

Figure 1.. Study Population.

Of 478 participants in the Research Electronic Data Capture (REDCap) database, 353 were assessed with the use of the Coma Recovery Scale–Revised (CRS-R) and at least one command-following paradigm on functional magnetic resonance imaging (fMRI) or electroencephalography (EEG) within 7 days. We defined cognitive motor dissociation operationally on the basis of the CRS-R assessment as a lack of responses to commands and a lack of intelligible speech in the context of a response to a task-based fMRI paradigm, a task-based EEG paradigm, or both. Cognitive motor dissociation occurred in 25% of the participants with no observable response to commands (participants with a behavioral diagnosis of coma or vegetative state [unconscious] or minimally conscious state–minus [the presence of signs of conscious awareness without responses to commands or intelligible verbal output]). Among the participants with an observable response to commands (participants with a behavioral diagnosis of minimally conscious state–plus [defined as the presence of signs of conscious awareness that include responses to commands or intelligible verbal output] and those who had emerged from the minimally conscious state [defined as the return of the ability to use common objects in a functional manner or correctly respond to basic yes-or-no questions about situational orientation]), 62% did not have a response on task-based fMRI, EEG, or both. Participants who had a response to commands on imaging were those with a response to commands on fMRI, EEG, or both, regardless of whether they underwent one or both imaging studies. Participants who did not have a response to commands on imaging were those who underwent fMRI only, EEG only, or both and had no response to commands on imaging.