Near-Infrared Spectroscopy to Assess Covert Volitional Brain Activity in Intensive Care

BACKGROUND: Detecting covert consciousness in unresponsive patients is challenging. Although functional magnetic resonance imaging and advanced electroencephalography paradigms can identify volitional brain activity, the limited accessibility of these technologies necessitates alternative approaches. Functional near-infrared spectroscopy may provide a portable solution in the intensive care unit. We assessed the feasibility of functional near-infrared spectroscopy with verbal motor commands to detect volitional brain activity in acute disorders of consciousness (DoC).

METHODS: Functional near-infrared spectroscopy recordings and clinical assessments were obtained from 50 patients with DoC with acute brain injury, with data analyzed post hoc and visually at the bedside. Twenty healthy volunteers served as controls.

RESULTS: After quality control, data from 19 controls and 36 patients were analyzed. Cortical activation was detected in 18 (96%) controls and 16 (44%) patients. Among 13 minimally conscious patients, volitional activity was found in 8 (62%), whereas 8 (35%) of 23 clinically unresponsive patients showed activation. Volitional brain activity in the latter was associated with higher odds of command following within a week, although it was not statistically significant (odds ratio 3.1, 95% confidence interval 0.7-15.8; p = 0.14). Visual bedside analysis showed high specificity (90%) but moderate agreement (κ = 0.4) with post hoc computational analysis.

CONCLUSIONS: Functional near-infrared spectroscopy with motor commands can detect volitional brain activity in acute DoC, although data quality issues remain a limitation.