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

Raffaele Ferri, Francesco Rundo, Mauro Manconi, Giuseppe Plazzi, Oliviero Bruni, Alessandro Oldani, Luigi Ferini-Strambi, Marco Zucconi

Research output: Contribution to journalArticlepeer-review


Objective: 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. Subjects and methods: 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. Results: 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. Conclusions: 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.

Original languageEnglish
Pages (from-to)947-949
Number of pages3
JournalSleep Medicine
Issue number9
Publication statusPublished - Oct 2010


  • Atonia index
  • Multiple system atrophy
  • Obstructive sleep apnea syndrome
  • Quantitative analysis
  • REM sleep behavior disorder
  • Submentalis EMG

ASJC Scopus subject areas

  • Medicine(all)


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