Improved computation of the atonia index in normal controls and patients with REM sleep behavior disorder

Sleep Research Centre, Department of Neurology I.C., Oasi Institute for Research on Mental Retardation and Brain Aging (IRCCS), Via C. Ruggero 73, Troina, Italy.
Sleep Medicine (Impact Factor: 3.15). 10/2010; 11(9):947-9. DOI: 10.1016/j.sleep.2010.06.003
Source: PubMed


The aim of this study was to evaluate the effects of a simple method of noise reduction before the calculation of the REM sleep atonia index (AI) on a large number of recordings from different normal controls and patient groups.
Eighty-nine subjects were included: 25 young controls, 10 aged controls, 31 untreated patients with idiopathic REM sleep behavior disorder (iRBD), 8 treated patients with iRBD, 10 patients with multiple system atrophy (MSA) and 5 patients with obstructive sleep apnea syndrome (OSAS). The average amplitude of the rectified submentalis muscle EMG signal was then obtained for all 1-s mini epochs of REM sleep. The new correction method was implemented by subtracting from each mini epoch the minimum value found in a moving window including the 60 mini epochs surrounding it.
Two arbitrary thresholds were established at AI<0.8 and 0.8<AI<0.9; all young controls presented AI>0.9; this was not true for aged controls, 3 of whom presented 0.8<AI<0.9 but none had AI<0.8; on the contrary 74.4% of all iRBD showed AI<0.9, with 38.5% of the whole group having AI<0.8 and only 25.6% with AI>0.9. All MSA patients showed AI<0.8.
After the introduction of this new method for noise reduction, REM sleep AI index values lower than 0.8 were strongly indicative of altered (reduced) chin EMG atonia during REM sleep; values of AI between 0.8 and 0.9 indicated a less evident involvement of atonia, and values above 0.9 characterized the majority of normal recordings.

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    • "The sleep respiratory pattern was normal (apnea/hypopnea index 3.8/hour). Finally, during REM sleep an excessive amount of tonic and phasic chin EMG activations was evident with a moderate decrease of the REM sleep atonia index (0.82) [26, 27]. During the subsequent MSLT, the patient fell asleep in all of the 5 sessions with a mean sleep latency of 5 min and 36 s; no sleep-onset REM episodes were recorded. "
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    ABSTRACT: A patient is reported in whom signs and symptoms of REM sleep behavior disorder (RBD) and narcolepsy have been associated for almost two decades with a late development of parkinsonism and rheumatoid arthritis. A 78-year-old male patient in whom RBD was first diagnosed was followed-up by clinical examination, videopolysomnography, multiple sleep latency test, cerebral magnetic resonance imaging, and dopamine transporter imaging by single-photon emission computerized tomography. The patient was found to present for almost two decades, in addition to RBD, also narcolepsy. Moreover, a late development of parkinsonism and the occurrence of rheumatoid arthritis were detected and clinically and instrumentally characterized. Patients predisposed to RBD and later parkinsonism might be susceptible to a variety of triggers that, in our patient, might have been represented by a possible latent autoimmune process leading to the development of narcolepsy with cataplexy and rheumatoid arthritis, later.
    Behavioural neurology 04/2013; 2014. DOI:10.3233/BEN-120340 · 1.45 Impact Factor
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    • "To calculate atonia index values, the rectified chin EMG signal was subdivided into 1-s miniepochs , and the average amplitude of each of these was calculated. Then, we applied a correction method which subtracted from each mini-epoch average rectified EMG amplitude, the minimum value found in a moving window including the 60 mini-epochs surrounding it (Ferri et al., 2010). Atonia index was defined as the ratio between the percentage of EMG mini-epochs with an average amplitude of ≤1 μV and the total mini-epochs excluding those with 1 μV < averaged EMG amplitude ≤2 μV. "
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    ABSTRACT: The authors hypothesized that if locomotor drive increases along with rapid eye movement (REM) sleep without atonia in idiopathic REM sleep behavior disorder (RBD), then RBD patients would have greater corticomuscular coherence (CMC) values during REM sleep than at other sleep stages and than in healthy control subjects during REM sleep. To explore this hypothesis, we analyzed beta frequency range CMC between sensorimotor cortex electroencephalography (EEG) and chin/limb muscle EMG in idiopathic RBD patients. Eleven drug naive idiopathic RBD patients and 11 age-matched healthy control subjects were included in the present study. All participants completed subjective sleep questionnaires and underwent polysomnography for one night. The CMC value between EEGs recorded at central electrodes and EMGs acquired at leg and chin muscles were computed and compared by repeated measures analysis of variance (ANOVA). Sleep stages and muscle (i.e., chin vs. leg) served as within-subject factors, and group served as the between-subject factor. Repeated measures ANOVA revealed no significant main effect of group (F(1,20) = 0.571, p = 0.458) or muscle (F(1,20) = 1.283, p = 0.271). However, sleep stage was found to have a significant main effect (F(2.067,41.332) = 20.912, p < 0.001). The interaction between group and sleep stage was significant (F(2.067,41.332) = 3.438, p = 0.040). RBD patients had a significantly higher CMC value than controls during REM sleep (0.047 ± 0.00 vs. 0.052 ± 0.00, respectively, p = 0.007). This study reveals increased CMC during REM sleep in patients with RBD, which indicates increased cortical locomotor drive. Furthermore, this study supports the hypothesis that sufficient locomotor drive plays a role in the pathophysiology of RBD in addition to REM sleep without atonia.
    Frontiers in Neurology 04/2012; 3:60. DOI:10.3389/fneur.2012.00060
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    • "The average amplitude of the rectified submentalis muscle EMG signal was then obtained for each mini-epoch. Then a noise reduction method was implemented (Ferri et al., 2010) by subtracting from the average Table 1 Demographic features of the subject groups "
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    ABSTRACT: The current definition of rapid eye movement (REM) sleep without atonia has no quantitative character, and cut-off values above which the level of electromyographic tone can be considered to be 'excessive' are unclear. The aim of this study was to analyse the characteristics of chin electromyographic amplitude by means of an automatic approach in a large group of normal controls, subdivided into different age groups. Eighty-eight normal controls were included, subdivided into six age groups: preschoolers (≤6 years); schoolers (6-10 years); preadolescents (10-13 years); young adults (24-40 years); middle-aged (58-65 years); and old (>65 years). The average amplitude of the rectified submentalis muscle electromyographic signal was used for the computation of the REM sleep Atonia Index. Chin muscle activations were detected, and their amplitude, duration and interval analysed. REM sleep Atonia Index showed a progressive and rapid increase from the preschool age to school and preadolescent age, reaching the maximum in the young adult group; after this age a small decline was observed in the middle-aged and old subjects. Conversely, the number of movements per hour in REM sleep showed a 'U'-shaped distribution across these age groups, with the minimum in the preadolescent group and the two extremes (preschool age and old) showing similar average levels of activity. Our results show that REM sleep atonia develops continuously during the lifespan, and undergoes complex changes with different developmental trajectories for REM atonia and electromyographic activations during REM sleep. Different mechanisms might subserve these two phenomena and their differential developmental dynamics.
    Journal of Sleep Research 09/2011; 21(3):257-63. DOI:10.1111/j.1365-2869.2011.00958.x · 3.35 Impact Factor
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