Covert Tracking to Visual Stimuli in Comatose Patients With Traumatic Brain Injury

ObjectivesThis study investigated video eye-tracking (VET) in comatose traumatic brain injury (TBI) patients. Methods We recruited healthy participants and unresponsive TBI patients. We surveyed the patients’ clinicians on whether the patient was tracking and performed the Coma Recovery Scale Revised (CRS-R). We recorded eye movements in response to motion of a finger, a face, a mirror, and an optokinetic stimulus using VET glasses. Patients were classified as “covert tracking” (tracking on VET only), and “overt tracking” (VET and clinical exam). The ability to obey commands was evaluated at 6-month follow-up. Results We recruited 20 healthy participants and 10 TBI patients. The use of VET was feasible in all participants and patients. Two patients demonstrated “covert tracking” (CRS-R of 6, 8), two demonstrated “overt tracking” (CRS-R 22, 11), and six patients had “no tracking” (CRS-R 8, 6, 5, 7, 6, 7). Five of 56 (9%) of tracking assessments were missed on clinical exam. All patients with tracking recovered consciousness at follow-up while only 2 out of 6 patients without tracking recovered at follow-up. Discussion VET is a feasible method to measure covert tracking. Future studies are needed to confirm the prognostic value of covert tracking.