Covert Consciousness in Acute Brain Injury Revealed by Automated Pupillometry and Cognitive Paradigms

Area of Science:

• Neuroscience
• Medical Technology
• Critical Care Medicine

Background:

• Identifying covert consciousness in intensive care unit (ICU) patients with disorders of consciousness (DoC) is critical for treatment.
• Sensitive, low-cost bedside markers for detecting residual consciousness are currently lacking.

Purpose of the Study:

• To investigate if automated pupillometry combined with cognitive paradigms can detect residual consciousness in ICU patients with DoC.
• To assess the utility of passive and active cognitive tasks in identifying covert awareness.

Main Methods:

• Prospective enrollment of clinically low-response or unresponsive ICU patients with DoC.
• Automated pupillometry recorded pupillary dilation responses to passive (visual, auditory) and active (mental arithmetic) cognitive paradigms.
• Comparison with age- and sex-matched healthy controls.

Main Results:

• Active cognitive paradigms, particularly mental arithmetic, differentiated between states of consciousness.
• Clinically unresponsive patients showed 17.8% detection of cognitive effort, while clinically low-responsive patients showed 50.0% detection (OR 4.56, p < 0.001).
• Healthy controls demonstrated 76.9% detection; results were consistent across sensitivity analyses.

Conclusions:

• Automated pupillometry with mental arithmetic reliably identifies cognitive efforts and covert consciousness in ICU patients with acute DoC.
• This technique offers a promising low-cost bedside tool for assessing consciousness levels.
• One case highlighted prolonged cognitive-motor dissociation, showing command-following before overt awareness.