Actigraphy assessments of circadian sleep-wake cycles in the Vegetative and Minimally Conscious States
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RESEARCH ARTICLE
Open Access
Actigraphy assessments of circadian sleep-wake cycles in the Vegetative and Minimally Conscious States Damian Cruse1*, Aurore Thibaut2, Athena Demertzi2, Julia C Nantes1, Marie-Aurélie Bruno2, Olivia Gosseries2, Audrey Vanhaudenhuyse2, Tristan A Bekinschtein3, Adrian M Owen1 and Steven Laureys2 See related commentary here http://www.biomedcentral.com/1741-7015/11/19
Abstract Background: The Vegetative and Minimally Conscious States (VS; MCS) are characterized by absent or highly disordered signs of awareness alongside preserved sleep-wake cycles. According to international diagnostic guidelines, sleep-wake cycles are assessed by means of observations of variable periods of eye-opening and eyeclosure. However, there is little empirical evidence for true circadian sleep-wake cycling in these patients, and there have been no large-scale investigations of the validity of this diagnostic criterion. Methods: We measured the circadian sleep-wake rhythms of 55 VS and MCS patients by means of wrist actigraphy, an indirect method that is highly correlated with polysomnographic estimates of sleeping/waking. Results: Contrary to the diagnostic guidelines, a significant proportion of patients did not exhibit statistically reliable sleep-wake cycles. The circadian rhythms of VS patients were significantly more impaired than those of MCS patients, as were the circadian rhythms of patients with non-traumatic injuries relative to those with traumatic injuries. The reliability of the circadian rhythms were significantly predicted by the patients’ levels of visual and motor functioning, consistent with the putative biological generators of these rhythms. Conclusions: The high variability across diagnoses and etiologies highlights the need for improved guidelines for the assessment of sleep-wake cycles in VS and MCS, and advocates the use of actigraphy as an inexpensive and non-invasive alternative. Keywords: Vegetative State, Minimally Conscious State, circadian rhythms, sleep, actigraphy
Background The Vegetative State (VS) or Unresponsive Wakefulness Syndrome (UWS [1]) is thought to reflect the dissociation of the two primary components of consciousness awareness and wakefulness [2,3]. A common tool for the assessment of awareness is the Coma Recovery Scale Revised [4] (CRS-R) which includes subscales designed to assess a range of functions, including auditory, visual, motor, verbal, communication and arousal. A braininjured patient is considered to possess awareness if * Correspondence: [email protected] 1 Brain and Mind Institute, University of Western Ontario, 1151 Richmond Street, London, ON N6A 3K7, Canada Full list of author information is available at the end of the article
they produce non-reflexive responses to stimulation, such as tracking an object that is moving in front of the eyes, or following a verbal command. Patients in the VS do not produce non-reflexive behavior and are, therefore, considered to lack awareness [5,6]. Patients in the Minimally Conscious State (MCS) exhibit some repro
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