Observation of Wakefields and Resonances in Coherent Synchrotron Radiation.

We report on high resolution measurements of resonances in the spectrum of coherent synchrotron radiation (CSR) at the Canadian Light Source (CLS). The resonances permeate the spectrum at wave number intervals of 0.074 cm(-1), and are highly stable under changes in the machine setup (energy, bucket filling pattern, CSR in bursting or continuous mode). Analogous resonances were predicted long ago in an idealized theory as eigenmodes of a smooth toroidal vacuum chamber driven by a bunched beam moving on a circular orbit. A corollary of peaks in the spectrum is the presence of pulses in the wakefield of the bunch at well-defined spatial intervals. Through experiments and further calculations we elucidate the resonance and wakefield mechanisms in the CLS vacuum chamber, which has a fluted form much different from a smooth torus. The wakefield is observed directly in the 30-110 GHz range by rf diodes, and indirectly by an interferometer in the THz range. The wake pulse sequence found by diodes is less regular than in the toroidal model, and depends on the point of observation, but is accounted for in a simulation of fields in the fluted chamber. Attention is paid to polarization of the observed fields, and possible coherence of fields produced in adjacent bending magnets. Low frequency wakefield production appears to be mainly local in a single bend, but multibend effects cannot be excluded entirely, and could play a role in high frequency resonances. New simulation techniques have been developed, which should be invaluable in further work.

EEG synchronisation during sleep-related epileptic seizures as a new tool to discriminate confusional arousals from paroxysmal arousals: preliminary findings.

Confusional arousals, paroxysmal arousals (as part of the nocturnal frontal lobe epilepsy) and normal arousals and awakenings from NREM sleep are frequently a challenge for differential diagnosis. In this article we describe the course of synchronisation between different EEG channels during nocturnal seizures in 3 patients with sleep-related epileptic seizures and in 1 patient with sleep terrors. The functional interactions between the different EEG channels during the nocturnal seizures were analysed by means of the so-called synchronisation likelihood (SL). SL is a measure of the dynamical (linear and nonlinear) interdependencies between a time series (EEG channel) and one or more other time series. The main results of our study are the confirmation of a significant increase in EEG synchronisation during sleep-related seizures and the indication that clinically similar ictal motor patterns might be generated by different neurophysiological mechanisms, characterised by different patterns of synchronisation involving multiple or single frequency bands. This new approach might be useful to differentiate motor seizures, emerging from NREM sleep, from parasomnias (arousal disorders) when both ictal and interictal EEGs are uninformative.

Nocturnal paroxysmal arousals with motor behaviors during sleep: frontal lobe epilepsy or parasomnia?

Nocturnal paroxysmal arousals with motor behaviors have been described in a few individuals, and their possible epileptic origin as nocturnal frontal lobe seizures has been suggested. However, the clinical and polysomnographic differentiation from parasomnias and physiologic movements during sleep have not been clarified yet. In this study, we evaluated a group of patients with nocturnal motor behaviors and tried to characterize paroxysmal arousals. Thirty-four participants (mean [+/-SD] age 22.7 [+/-12.9] years) noting nocturnal motor agitation or behaviors and 12 healthy controls (mean age 24.1 [+/-3.1] years) underwent nocturnal polysomnography with video-tape recording and motor behaviors analysis. Arousals with motor attacks were classified as minimal, minor, or major depending on semiology, complexity, and duration of behaviors. All patients showed several minimal (e.g., scratching or rubbing the nose and the head) and minor (e.g., pelvic thrusting or swinging with dystonic component) attacks, and 53% also had major episodes (e.g., sudden elevation of the head and trunk from the bed with complex behaviors) occurring mainly in non-rapid eye movement sleep. In all the patients, motor attacks were characterized by stereotypy, sudden onset, short duration, and repetitiveness. In 80%, epileptiform abnormalities were found. All control subjects showed motor events, but they were fewer, slower, nonstereotyped, and semiologically different from the patients'. No significant difference in conventional sleep parameters between the two groups were found. Paroxysmal arousals with motor behaviors probably represent a particular form of nocturnal frontal lobe epilepsy rather than an unusual parasomnia. The semiologic characteristics of these type of arousals are difficult to recognize and differentiate from physiologic movements or parasomnias without video-polygraphic analysis.

Autosomal dominant nocturnal frontal lobe epilepsy: electroclinical picture.

PURPOSE: Nocturnal frontal lobe epilepsy is a disorder that is difficult to diagnose because its clinical presentation is often limited to motor behavior during sleep. For this reason, a misleading diagnosis of benign nocturnal parasomnias might be possible. Recently, an inherited form of nocturnal frontal lobe epilepsy was described in some families. The aim of our work was to describe the electroclinical pattern of a sample of familial cases with this syndrome. METHODS: We observed 33 patients, all complaining of frequent nocturnal motor attacks, from eight Italian families. The family trees were strongly supportive of autosomal dominant inheritance. We performed a full-night video-polysomnographic monitoring in 12 patients. RESULTS: The recordings showed attacks in all patients, there being a widespread pattern of motor activity. Ictal and interictal EEG abnormalities were often hidden and, unless associated with a video recording, were of no use for the final diagnosis. Intraindividual stereotypy, abrupt onset, and semiology of attacks allowed differentiation from healthy subjects' nocturnal motor behavior. CONCLUSIONS: Autosomal dominant nocturnal frontal lobe epilepsy is probably not uncommon. Full-night video-polysomnographic monitoring is fundamental for the differential diagnosis of benign parasomnias and, consequently, for appropriate therapy.