Loss of rapid eye movement sleep atonia in patients with REM sleep behavioral disorder, narcolepsy, and isolated loss of REM atonia

Abstract

Study objectives: To compare the amounts of REM sleep without atonia (RSWA) between patients with REM sleep behavior disorder (RBD), "isolated loss of REM atonia," narcolepsy, and control subjects and determine if there were threshold values for the amount of RSWA that differentiate each group from controls.

Methods: Retrospective analyses of polysomnography (PSG) records were used employing strict quantitative criteria for the measurement of phasic and tonic EMG activity during REM sleep. The PSG recordings of 47 individuals were analyzed (RBD 16, isolated loss of REM atonia 11, narcolepsy 10, control 10).

Results: Patients with the diagnosis of isolated loss of REM atonia had significantly lower levels of EMG activity during REM sleep than those with RBD but higher than control subjects. RSWA was higher in narcolepsy than in loss of REM atonia but lower than for RBD patients. Receiver operating characteristic (ROC) curves provided threshold values with high specificity and sensitivity in all patient groups with a cutoff value ≥ 1.22% (100% correctly classified) for phasic and ≥ 3.17% for tonic (92% correctly classified) EMG activity in RBD.

Conclusion: Quantification of REM sleep EMG activity can successfully differentiate RBD and isolated loss of REM atonia patients from controls. The consistently increased amount of RSWA in patients with narcolepsy indicates that this can be an additional marker for a diagnosis of narcolepsy. Longitudinal studies of patients with isolated loss of REM atonia are needed to evaluate if these patients are at risk of developing RBD or neurodegenerative disorders.

Keywords: EMG; REM sleep; REM sleep behavior disorder (RBD); narcolepsy; polysomnography.

Figure 1. Box plots for tonic (left) and phasic (right) EMG muscle activity for all the studied groups

The graph displays summary of the group values of REM sleep proportion with tonic and phasic EMG activity: median, 25th and 75th interquartile ranges (IQR), minimum and maximum data values. RBD, REM sleep behavior disorder; ILRA, isolated loss of REM atonia.

Figure 2

(A) Dot plot of individual data for controls versus patients with RBD. For tonic activity (left), the cutoff value of amount of REM sleep with EMG activity (indicated as horizontal line on the graph) was ≥ 3.17%, (95% CI 0.75-1, sensitivity 87%, specificity 100%, with 92% correctly classified and area under curve = 0.92). For phasic activity (right), the cutoff value was ≥ 1.22% (sensitivity, specificity, and correctly classified 100%. 95% CI 1 and area under curve = 1). (B) Dot plot of individual data for controls versus patients with “isolated loss of REM atonia.” For tonic activity (left), the cutoff value of amount of REM sleep with EMG activity ≥ 1.28 (95% CI 0.51-0.96, sensitivity 63%, and specificity 90%, with 76% correctly classified and area under curve = 0.74). For phasic activity (right), the cutoff value was ≥ 1.12% (95% CI 0.94-1, sensitivity 90%, and specificity 100%, with 95% correctly classified and area under curve = 0.98). (C) Dot plot of individual data for controls versus patients with narcolepsy. For tonic activity (left) the cutoff value of amount of REM sleep with EMG activity ≥ 1.48 (95% CI 0.8-1, sensitivity 80%, and specificity 90%, with 85% correctly classified and area under curve = 0.92). For phasic activity (right) the cutoff value was ≥ 2.0 (95% CI 0.76-1, sensitivity 90%, and specificity 100%, with 95% correctly classified and area under curve = 0.92).

Figure 3. Receiver operating characteristic (ROC) graphs of tonic activity (left) and phasic activity (right)

(A) RBD, (B) ILRA (isolated loss of REM atonia), and (C) narcolepsy patients. ROC curve for the tonic EMG activity in RBD (AUC-1, 95% Confidence interval -1, sensitivity, specificity, and correctly classified 100%) is not generated by the software.