Sleeping well
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COMMENTARY
Open Access
Sleeping well Mithu Sen and G Bryan Young* See related research article here http://www.biomedcentral.com/1741-7015/11/18
Abstract In a study by Cruse et al. published in BMC Medicine, patients with severe brain damage who were in the Vegetative or Minimally Conscious States (VS or MCS, respectively) from traumatic and nontraumatic etiologies had assessments of circadian rhythms using an actigraph, a device worn on a limb to evaluate circadian rhythmicity, in this population. This is a novel approach and is being used as a surrogate for polysomnography and other reference standards. Cruse et al. showed more disruption in circadian rhythms in the VS when compared to the MCS. This suggests that more brain injury occurs in the areas that control circadian rhythmicity in VS than in MCS patients. The study provides opportunities for improved prognostication and rehabilitation strategies in this patient population. Keywords: vegetative state, minimally conscious state, actigraphy, circadian rhythm
Commentary Sleep is the golden chain that ties health and our bodies together. (Thomas Dekker) The Vegetative and Minimally Conscious States (VS and MCS, respectively) are severe disorders of consciousness that reflect severe brain dysfunction/damage. Vegetative patients have preserved vegetative functions (temperature, hemodynamic and hormonal regulation and breathing) and are awake (with arousability with eye opening and sleep-wake cycles) but show no behavioral evidence of awareness (no eye contact, tracking, obeying of commands or emotional responses). Minimally conscious patients show minimal and limited but definite evidence of some aspect(s) of awareness, for example, visual tracking, movements or emotional responses triggered by relevant environmental stimuli, even very * Correspondence: [email protected] Department of Medicine, Division of Critical Care Medicine, Western University, London, Ontario, N6A 5A5, Canada
simple command-following or verbalization as isolated phenomena. Cruse and colleagues report the results of actigraphy assessments of circadian sleep-wake rhythms in patients with VS and MCS in research published in BMC Medicine [1]. They studied patients with traumatic and nontraumatic brain injury at widely ranging intervals from the ictus (0 to 290 months). Actigraphy uses a watchshaped device that is strapped to the arm and is used to measure limb movements in sleep as a surrogate for estimating the sleep-wake cycle. The actigraphs (or actimeters) can provide patterns of activity that can be used to outline circadian rhythms [2]. Four distinct aspects of movement are captured: amplitude, acrophase (the point in the sleep-wake cycle when activity is maximal), the mesor (the mean of the rhythm) and a goodness-of-fit curve to show the robustness of the circadian rhythm. This methodology has been previously validated by comparing the results with standard polysomnography [2]. The principal finding was that as a group VS patients (n = 18) had more significantly disrupted circa
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