Sleep in the Unresponsive Wakefulness Syndrome and Minimally Conscious State

Abstract

The goal of our study was to investigate different aspects of sleep, namely the sleep-wake cycle and sleep stages, in the vegetative state/unresponsive wakefulness syndrome (VS/UWS), and minimally conscious state (MCS). A 24-h polysomnography was performed in 20 patients who were in a UWS (n = 10) or in a MCS (n = 10) because of brain injury. The data were first tested for the presence of a sleep-wake cycle, and the observed sleep patterns were compared with standard scoring criteria. Sleep spindles, slow wave sleep, and rapid eye movement sleep were quantified and their clinical value was investigated. According to our results, an electrophysiological sleep-wake cycle was identified in five MCS and three VS/UWS patients. Sleep stages did not always match the standard scoring criteria, which therefore needed to be adapted. Sleep spindles were present more in patients who clinically improved within 6 months. Slow wave sleep was present in eight MCS and three VS/UWS patients but never in the ischemic etiology. Rapid eye movement sleep, and therefore dreaming that is a form of consciousness, was present in all MCS and three VS/UWS patients. In conclusion, the presence of alternating periods of eyes-open/eyes-closed cycles does not necessarily imply preserved electrophysiological sleep architecture in the UWS and MCS, contrary to previous definition. The investigation of sleep is a little studied yet simple and informative way to evaluate the integrity of residual brain function in patients with disorders of consciousness with possible clinical diagnostic and prognostic implications.

Disorders of consciousness after acquired brain injury: the state of the science

“…115 A 24-h polysomnography study observed behavioural (eyes open or closed) but not electrophysiological sleep-wake patterns in VS. 116 Using high-density EEG, a homoeostatic decline of EEG slow-wave activity through the night (possibly reflecting residual synaptic plasticity) and periods of REM sleep (possibly reflecting 'dreaming') could be demonstrated in MCS but not in VS. 117 Event-related potentials (ERPs) are averaged EEG epochs to external or cognitive events. 118 In comatose patients, the absence of a cortical response to electrical stimulation of the median nerves during somatosensory ERP recordings is associated with poor outcome, especially after anoxic injury, 119 although treatment by hypothermia might challenge the prognostic utility of this approach.…”

Assessing consciousness in coma and related states using transcranial magnetic stimulation combined with electroencephalography

“…Although recovery of the sleep-wake cycle is part of the criteria of UWS, recent studies have demonstrated an absence of electrophysiological characteristics of sleep in UWS [10,11]. Brain metabolism is usually diminished by 40 to 50% with impaired cortico-thalamo-cortical circuits but relatively preserved brainstem functions [12].…”

Study of Sleep Patterns Might Advance Our Knowledge on Alertness in Traumatic Brain Injury

“…Also, researchers have utilized EMG in an attempt to distinguish central from obstructive sleep apnea (SA) and concluded that the diaphragmatic EMG could be a useful technique in assessing neural respiratory drive and respiratory effort and, therefore, in accurately distinguishing the two forms of sleep apnea (SA). This is particularly relevant to the TBI population as, according to a report by Cologan et al [10], the majority of the events in their TBI sample were central in nature rather than obstructive, while in the general population, sleep apnea (SA) consists of 90% obstructive and only 10% central events [35].…”

“…Similarly, Cologan and colleagues proposed that the presence of EEG patterns resembling normal human sleep [9] (i.e. well-structured patterns of non rapid eye movement and/or rapid eye movement (REM) sleep)can be markers of a favorable outcome after brain injury [10]. Moreover, the quality and quantity of spindles can provide a new index of the severity of thalamocortical injury, in accordance with brain imaging studies showing the correlation between the extent of thalamus damage and behavioral disability and outcome in disorders of consciousness [10][11][12][13].Gosselin and colleagues observed increased delta and decreased alpha activity during wakefulness in patients with mild TBI and proposed sleep intrusions in the waking state might indicate continuous sleep inertia, manifesting as fatigue and impaired functioning [14].…”

“…well-structured patterns of non rapid eye movement and/or rapid eye movement (REM) sleep)can be markers of a favorable outcome after brain injury [10]. Moreover, the quality and quantity of spindles can provide a new index of the severity of thalamocortical injury, in accordance with brain imaging studies showing the correlation between the extent of thalamus damage and behavioral disability and outcome in disorders of consciousness [10][11][12][13].Gosselin and colleagues observed increased delta and decreased alpha activity during wakefulness in patients with mild TBI and proposed sleep intrusions in the waking state might indicate continuous sleep inertia, manifesting as fatigue and impaired functioning [14]. The clinical significance of the utility of EEG in TBI is reflected in a recent study by Teel et al [15].While concussed participants passed all clinical concussion testing tools, they showed path physiological dysfunction with evaluation of EEG variables,supporting the hypothesis of diminishedbrain resources to compensate appropriately during activity [15].The results of the study areparticularly relevant to clinicians who make return-toplay or return-to-work decisions (i.e.…”