Can fast-component of nystagmus on caloric vestibulo-ocular responses predict emergence from vegetative state in ICU?

The aim of the study was to determine if bedside caloric vestibulo-ocular responses (VOR) are able to predict consciousness recovery from clinically determined vegetative state (VS) in the ICU. Twenty-six severely brain injured patients that were clinically in VS were included. Horizontal VOR were tested at bedside by cold-water irrigation of the external auditory canal. Visual inspection evaluated the presence of a slow drift toward the side of stimulation (slow-component of nystagmus or tonic deviation) as well as the presence of a rapid compensatory movement/jerk back to the midline (fast-component of nystagmus). Patients were then divided into two groups according to whether they eventually regained consciousness or not. Patients were 59 ± 21 years old. Thirteen out of 26 patients ultimately recovered consciousness and 13 remained unconscious. Thirteen patients (100%) presented a slow-component of nystagmus during VOR testing in the group that recovered consciousness and 11 (85%) in the group that remained unconscious. All the patients that recovered consciousness (13, 100%) presented a fast-component of nystagmus during VOR testing compared to only one of 11 patients (8%) in the group that remained unconscious. Sensitivity of fast-component of nystagmus during VOR testing to predict recovering of consciousness was 1.00, specificity was 0.92, positive predictive value was 0.93 and negative predictive value was 1.00. Bedside VOR testing in clinically VS patients seems able to predict consciousness recovery from vegetative state and could help to preclude active medical treatment withdrawal and to indicate the need for further complementary explorations, i.e. event-related potentials, functional MRI or PET-scan.