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

• Published in: Neurocritical care 2024-08, Vol.41 (1), p.218-227
• Main Authors: Othman, Marwan H., Olsen, Markus Harboe, Hansen, Karen Irgens Tanderup, Amiri, Moshgan, Jensen, Helene Ravnholt, Nyholm, Benjamin, Møller, Kirsten, Kjaergaard, Jesper, Kondziella, Daniel
• Format: Article
• Language: English
• Subjects: Automation; Cognitive load; Coma; Consciousness; Critical Care Medicine; Intensive; Intensive care; Internal Medicine; Medicine; Medicine & Public Health; Neurology; Neurosurgery; Original Work; Paradigms; Patients; Sound; Statistical analysis; Traumatic brain injury
• ISSN: 1541-6933; 1556-0961; 1556-0961
• DOI: 10.1007/s12028-024-01983-7

Background Identifying covert consciousness in intensive care unit (ICU) patients with coma and other disorders of consciousness (DoC) is crucial for treatment decisions, but sensitive low-cost bedside markers are missing. We investigated whether automated pupillometry combined with passive and active cognitive paradigms can detect residual consciousness in ICU patients with DoC. Methods We prospectively enrolled clinically low-response or unresponsive patients with traumatic or nontraumatic DoC from ICUs of a tertiary referral center. Age-matched and sex-matched healthy volunteers served as controls. Patients were categorized into clinically unresponsive (coma or unresponsive wakefulness syndrome) or clinically low-responsive (minimally conscious state or better). Using automated pupillometry, we recorded pupillary dilation to passive (visual and auditory stimuli) and active (mental arithmetic) cognitive paradigms, with task-specific success criteria (e.g., ≥ 3 of 5 pupillary dilations on five consecutive mental arithmetic tasks). Results We obtained 699 pupillometry recordings at 178 time points from 91 ICU patients with brain injury (mean age 60 ± 13.8 years, 31% women, and 49.5% nontraumatic brain injuries). Recordings were also obtained from 26 matched controls (59 ± 14.8 years, 38% women). Passive paradigms yielded limited distinctions between patients and controls. However, active paradigms enabled discrimination between different states of consciousness. With mental arithmetic of moderate complexity, ≥ 3 pupillary dilations were seen in 17.8% of clinically unresponsive patients and 50.0% of clinically low-responsive patients (odds ratio 4.56, 95% confidence interval 2.09–10.10; p