Twenty-five percent of patients with disorders of consciousness who appear unresponsive demonstrate brain activity during cognitive tasks, according to a recent study.
Researchers examined cognitive motor dissociation (CMD) in participants with disorders of consciousness (DOC). The prospective cohort study, published in The New England Journal of Medicine, involved 353 adults across six international centers, all diagnosed with varying levels of DOC, including coma, vegetative state, or minimally conscious state. Researchers assessed brain activity using task-based functional MRI (fMRI), electroencephalography (EEG), or both.
CMD, characterized by brain activity in response to cognitive tasks detected via fMRI or EEG, occurs in individuals who appear behaviorally unresponsive. This phenomenon—previously underexplored in large cohorts—may affect approaches to assessing consciousness and clinical management.
The study population had a median age of 37.9 years. Half of the participants had brain trauma as the cause of their condition, and the median duration between the brain injury and the assessment was 7.9 months.
Twenty-five percent (60 of 241) of participants who showed no observable response to commands were found to have CMD. Of those diagnosed with CMD, 18% were evaluated using only fMRI, 22% with only EEG, and 60% with both imaging techniques. CMD was identified in 38% (43 of 112) of participants who were able to respond to verbal commands, compared to 25% among those who did not show observable responses.
For 65% of participants, either fMRI or EEG data were available, while 35% had data from both fMRI and EEG. Coma Recovery Scale–Revised assessments were conducted within a median of 1 day of the fMRI and on the same day as the EEG. The proportion of participants diagnosed with CMD differed widely across the various study sites, with rates ranging from 2% to 45%.
The findings suggested that CMD may be more common than previously reported, particularly among younger individuals, those with traumatic brain injury, and those assessed at a greater length of time since their initial injury. The study authors concluded, "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."
Full disclosures can be found in the published study.
