Visual Pursuit: Within-Day Variability in the Severe Disorder of Consciousness

Abstract

Visual pursuit marks substantial recuperation from a vegetative state and evolution into a minimally-conscious state, but its incidence in different studies suggests some unreliability in contrast with its established prognostic relevance. Subjects in vegetative (n=9) or minimally-conscious (n=13) states were tested for visual pursuit 6 times/day (9:30, 10:30, and 11:30 am, and 2:00, 3:00, and 4.00 pm, for a total of 132 determinations). Visual pursuit was observed at all testing times in 8 minimally-conscious patients, and never in 5 subjects in a vegetative state. Its incidence per subject ranged from 50-100% of testing times in the minimally-conscious state (83±23%), and 0-33% in a vegetative state (7%±12), with spontaneous fluctuations during the day and maximal levels at 10.30 am and 3.00 pm, and was never observed at the post-prandial time point (2:00 pm). The overall chance of observing visual tracking at least once during the day was ∼33% in the vegetative state, whereas that of not observing it in the minimally-conscious state was ∼38%. These percentages are congruent with the reported misdiagnosis rate between the two conditions, and document spontaneous variability possibly related to circadian rhythms.

Detection of visual pursuit in patients in minimally conscious state: A matter of stimuli and visual plane?

“…Moreover, unsettled vigilance could also have impacted both studies by negatively affecting both the patients' performance and diagnosis. Indeed, a recent study showed that visual pursuit is particularly sensitive to withinday fluctuations in patient with MCS [39].…”

Sleep in the Unresponsive Wakefulness Syndrome and Minimally Conscious State

“…It is well known, however, that vigilance and awareness fluctuate in such patients, resulting in variable behaviors and cognitive performances. [2][3][4] At present, there is no standard description of the different vigilance states in VS/UWS and MCS patients.…”

Komunikacja w grupie pacjentów z zaburzeniami świadomości – wnioskiz projektu InteRDoCTor

“…Presence of caregivers may decrease misdiagnosis percentage [22]. Within-day variability of diagnosis was high: it may achieve 33% in the VS/UWS and 38% in MCS [23]. What important assessment using GCS do not provide predictor that a patient is emerging from VS/UWS to an MCS [14].…”