Changes in cerebral and autonomic activity heralding periodic limb movements in sleep.

BACKGROUND AND PURPOSE: Periodic limb movement disorder (PLMD) is frequently accompanied by awakenings or signs of EEG arousal. However, it is matter of debate whether EEG arousals trigger leg movements or both EEG arousal and leg movements are separate expressions of a common pathophysiological mechanism. Previous studies showed that cardiac and cerebral changes occur in association with periodic limb movements (PLMs), and that a combining increase in delta activity and in heart rate (HR) occurs before the onset of PLMs. PATIENTS AND METHODS: This paper presents some preliminary data, obtained from a sample of 5 subjects with PLMD not associated to restless legs syndrome. To describe the temporal pattern of cardiac and EEG activities changes concomitant with PLMs in NREM sleep we used time frequency analysis technique. RESULTS: PLM onset is heralded by a significant activation of HR and delta activity power, beginning 4.25 and 3 s respectively before PLMs onset, with PLMs onset and arousal onset falling together. DISCUSSION: Delta and HR variations herald PLMs and activation of fast EEG frequencies. Such a stereotyped pattern is common in PLMs and in spontaneous or stimuli-induced arousals. Moreover a similar pattern seems to encompass the CAP phenomenon. The whole of these phenomena can be linked to the activity of a common brainstem system, which receives peripheral inputs, regulating the vascular, cardiac and respiratory activities and synchronizing them to cortical oscillations of EEG.

Modifications of sleep EEG induced by chronic vagus nerve stimulation in patients affected by refractory epilepsy.

OBJECTIVE: The aim of this study was to evaluate the impact of chronic vagus nerve stimulation (VNS) on sleep/wake background EEG and interictal epileptiform activity (IEA) of patients with medically refractory epilepsy. METHODS: From a broader sample of 10 patients subjected to baseline and treatment polysomnographies, spectral analysis and IEA count have been performed on 6 subjects' recordings, comparing the results by means of statistical analysis. RESULTS: An overall increase in EEG total power after VNS has been observed, more marked in NREM sleep; collapsing EEG power spectra into 5 frequency bands, we have found a statistically significant increase in delta and theta in NREM sleep, and of alpha in wakefulness and REM sleep. The incidence of IEA is diminished, although not significantly; only the duration of discharges is significantly diminished. CONCLUSIONS AND SIGNIFICANCE: Long-term VNS produces an enhancement in sleep EEG power of medically refractory epileptic patients. These results may be related to a better structured composition of EEG, and it is possible that chronic VNS may have a major role in enhancing the brain's ability to generate an electrical activity.

Impairment of the production of delta sleep in anorectic adolescents.

OBJECTIVE: Total sleep time and slow-wave sleep (SWS) are frequently reported to be reduced in anorectics. A preliminary study showed that slow-wave activity (SWA, 0.5-4.5 Hz) is decreased in anorectic adolescents. The present study investigates whether this reduction is the result of the increased sleep fragmentation or is dependent on an intrinsic weakness of SWA-producing mechanisms. DESIGN: Statistical analysis of spectral electroencephalogram data recorded during sleep from a group of anorectics and a control group. SETTING: Polysomnographic data were recorded in single rooms in the hospital for 1 night following an adaptation night. PARTICIPANTS: 20 adolescent anorectic girls (13.9 +/- 2.0 years) and 12 age-matched control subjects. INTERVENTIONS: Refeeding and psychotherapy. MEASUREMENTS AND RESULTS: Anorectics had an increase of wakefulness after sleep onset, a higher number of arousals, and a reduction of SWS and SWA during total sleep time. No relationship between the reduction of SWA and duration of illness was found, while a relationship between SWA decrease and the level of emaciation (body mass index) was present. The analysis limited to the first non-rapid eye movement sleep cycle did not show any difference between the 2 groups in the number of awakenings and arousals. Nevertheless, anorectics showed a reduction of SWS and SWA. CONCLUSIONS: Sleep of anorectic patients seems to be characterized by an impairment of SWA-producing mechanisms independent of the increased sleep fragmentation. This is probably related to the primary pathophysiologic characteristics of the illness but could also reflect secondary functional and anatomic alterations of the brain.

Chronic vagus nerve stimulation improves alertness and reduces rapid eye movement sleep in patients affected by refractory epilepsy.

OBJECTIVE: Our study aimed to evaluate the existence and entity of changes in sleep structure following vagus nerve stimulation in patients with refractory epilepsy. METHOD: A polysomnographic study was performed on the nocturnal sleep of 10 subjects with refractory epilepsy. Subjects were recorded both in baseline conditions and after chronic vagus nerve stimulation. Sleep parameters of the entire night were evaluated. Mean power value of slow-wave activity was computed in the first non-rapid eye movement sleep cycle. A sleep-wake diary evaluated quantity of both nocturnal and daytime sleep, while visual-analog scales assessed quality of sleep and wake. The differences between the 2 conditions underwent parametric and nonparametric statistical evaluation. RESULTS: Vagus nerve stimulation produced a significant reduction in REM sleep (in all subjects with vagus nerve stimulus intensity greater than 1.5 milliampere, but not in the only patient with a stimulus intensity less than 1.5 milliampere), along with an increase in the number of awakenings, percentage of wake after sleep onset, and stage 1 sleep. Data from a sleep-wake questionnaire show a decrease in both nocturnal sleep and daytime naps and an increased daytime alertness, while the quality of wakefulness is globally improved. Spectral analysis shows an enhancement of delta power during non-rapid eye movement sleep. CONCLUSIONS: Our data demonstrate major effects of vagus nerve stimulation on both daytime alertness (which is improved) and nocturnal rapid eye movement sleep (which is reduced). These effects could be interpreted as the result of a destabilizing action of vagus nerve stimulation on neural structures regulating sleep-wake and rapid eye movement/non-rapid eye movement sleep cycles. Lower intensity vagus nerve stimulation seems only to improve alertness; higher intensity vagus nerve stimulation seems able to exert an adjunctive rapid eye movement sleep-attenuating effect.