Cognitive Motor Dissociation Detected in 25% of Unresponsive Patients

Cognitive motor dissociation may be more common than previously understood, according to results of a prospective cohort study published in The New England Journal of Medicine. Cognitive motor dissociation, a phenomenon in which people who are unresponsive to commands due to severe brain injury demonstrate brain activity on functional MRI (fMRI) or EEG when presented with cognitive tasks, was previously thought to affect approximately 10% to 20% of people with disorders of consciousness. The present study identified cognitive motor dissociation in 1 in 4 of participants, with implications for the assessment of cognitive activity in patients with disorders of consciousness.

The prospective cohort study was conducted at 6 international centers, collecting clinical, behavioral, and task-based fMRI and EEG data for 353 adult participants with disorders of consciousness related to traumatic brain injury (TBI), cardiac arrest or hypoxia, and stroke, among others. Researchers conducted behavioral assessment using the the Coma Recovery Scale–Revised (CRS-R), dividing participants into 2 groups: those with an observable response to verbal commands (n=112) and those without an observable response (n=241). Only 122 participants (35%) received both fMRI and EEG assessment, whereas 231 received only fMRI or only EEG (65%) assessment. According to the definition used by the researchers, only participants without an observable response to verbal commands could be considered to have cognitive motor dissociation.

In terms of results:

• Cognitive motor dissociation was detected in 60 (25%) of the 241 participants without an observable response to verbal commands.
• Cognitive motor dissociation was associated with younger age, longer time since injury, and brain trauma as an etiologic factor.
• Brain trauma was an etiologic factor in 50% of study participants.
• Individuals assessed using both fMRI and EEG were more likely to be determined as having cognitive motor dissociation.

The researchers note that the rate of cognitive motor dissociation in these study findings are 5% to 10% higher than those measured in previous studies. Noted limitations include heterogenous strategies used in data acquisition, analysis, and interpretations. The researchers suggest that further efforts be made in the field to standardize, validate, and simplify fMRI and EEG methods for the detection of cognitive motor dissociation. Additionally, they state that further research should be conducted to determine whether detection of cognitive motor dissociation can lead to better outcomes for patients.