Cognitive Motor Dissociation in Disorders of Consciousness.
Level 3 - non-randomized controlled study
Prospective non-randomized multicenter cohort study.
PubMed 39141852 · doi:10.1056/NEJMoa2400645
What was done
In a prospective cohort study across six international centers, investigators evaluated 353 adults with disorders of consciousness using clinical assessment (Coma Recovery Scale-Revised [CRS-R]), task-based functional MRI (fMRI), and task-based electroencephalography (EEG). They tested for brain responses to commands in 241 patients without observable behavioral response to verbal commands (coma, vegetative state, or minimally conscious state-minus) and 112 patients with observable command-following. Modality availability was fMRI only or EEG only in 65% of participants, and both in 35%.
What was found
Cognitive motor dissociation was detected in 25% (60 of 241) of behaviorally unresponsive participants (11 evaluated by fMRI alone, 13 by EEG alone, and 36 by both). Detection was associated with younger age, traumatic brain injury (50% of the overall cohort), and longer duration post-injury (median time to assessment was 7.9 months). In comparison, task-based fMRI or EEG responses were detected in 38% (43 of 112) of participants who did exhibit observable behavioral responses to commands.
Why it matters
This large multicenter study shows that one in four behaviorally unresponsive patients with severe brain injuries retains measurable, covert cognitive capacity when assessed with advanced neuroimaging or electrophysiology.
Limits
The study relied on a convenience sample. Only 35% of participants underwent both fMRI and EEG testing, which may lead to underdetection in those receiving single-modality assessments. The abstract does not report whether covert command-following correlated with long-term functional recovery or altered clinical management.