Author
Questionnaire
Characteristics
Sensitivity (%)
Specificity (%)
Stiasny-Kolster et al. [9]
RBD Screening Questionnaire
10 items with 13 questions
96
56
Yes/no answers
Max score =13
Li et al. [11]
RBDQ-HK
13 questions
82
87
Assesses for life time and recent (1 year) occurrence
Boeve et al. [12]
Mayo Sleep Questionnaire
Contains an introductory question about RBD, followed by 5 subsequent questions about RBD symptoms
98
74
Postuma et al. [14]
Single question Screen for RBD
Single question
94
87
Frauscher et al. [13]
Innsbruck RBD Inventory
5 questions
91
86
Yes/no/do not know answers
Frauscher et al. [13]
RBD summary question (from Innsbruck RBD Inventory)
Single question
74
93
For example, a recent study demonstrates that even in a Parkinson’s disease population, the validity of the RBD questionnaire clearly depends on the setting, and where and how it is administered [16]. Even more importantly, 16 % false positives were obtained with a validated RBD screening questionnaire in healthy sleepers in whom RBD was later definitely excluded both by sleep expert interview and polysomnography [17, 18]. An unexpectedly high rate of RBD screening questionnaire positives, probably reflecting major false positive numbers, was also accumulated in a current research initiative to detect Parkinson’s disease progression markers in a Parkinson’s disease population versus a control population, in which 20 % of the healthy control group exceeded the RBD cut-off score (http://www.ppmi-info.org). Therefore, using a questionnaire alone must definitely be considered unreliable as a diagnostic instrument, even more so in the context of iRBD without any already diagnosed synucleinopathy, and when they are administered outside a study or hospital setting, or by untrained interviewers or as handouts only. Thus, the application of questionnaires alone without polysomnography can carry a substantial risk to both over- and underestimating RBD. This is of particular relevance in RBD as the clinical differential diagnosis is a challenging one. Patients with obstructive sleep apnea, a highly frequent disorder in the elderly, often exhibit violent limb movements in the arousal at the end of each apnea [19], and patients with RLS/PLM can have intense limb or whole body jerks [20]. Sleep-related seizures, non-REM parasomnias, psychiatric disorders, and drug-induced conditions are among the remaining differential diagnoses which are very difficult, if not impossible, to disentangle without PSG.
11.3 Polysomnographic Criteria for REM Sleep Without Atonia
The polysomnographic hallmark of RBD is the electromyographic demonstration of REM sleep without atonia. Current ICSD-criteria require polysomnographic evaluation as mandatory for a definite diagnosis of RBD [8]. It is defined qualitatively as “the EMG finding of excessive amounts of sustained or intermittent elevation of submental EMG tone or excessive phasic submental or (upper or lower) limb EMG twitching” [8]. As the qualitative assessment of REM sleep without atonia is dependent on the individual polysomnographic scorer, the current ICSD-3 criteria cite a normative study reporting that a total of 27 % of 30 s epochs which are positive for any (tonic/phasic or both) EMG activity in the chin or phasic activity detected in the bilateral flexor digitorum superficialis, reliably distinguish RBD patients from controls [21]. Examples of a 30 s epoch of normal REM sleep and of REM sleep without atonia are provided in Fig. 11.1.
Fig. 11.1
Examples of normal REM sleep and REM sleep without atonia. (a) Thirty sepoch of normal REM sleep. Note that few bursts of EMG activity are also present during normal REM sleep. (b) Thirty sepoch of REM sleep without atonia. Note increased levels of phasic EMG activity in the chin and the extremities. In the chin, there is in addition an increase of tonic background EMG activity
11.3.1 Manual Quantification of REM Sleep Without Atonia
Manual quantification of EMG activity during REM sleep was first performed in healthy normals in the mid-seventies and early eighties (for an overview, see [22]) REM sleep without atonia in the context of RBD was first systematically assessed by Lapierre and Montplaisir in 1992 [23], who classified EMG activity as “phasic” and “tonic” EMG activity within 2 s mini-epochs and 20 s epochs. Phasic EMG activity was defined as EMG activity between 0.1 and 5 s with an amplitude exceeding four times the background EMG, and tonic EMG activity was defined as the presence of tonic EMG activity for at least 50 % of the total epoch. This classification system is still the most widely used system for EMG quantification [21, 24–28]. Minor modifications of the original scoring system introduced by the various investigators concern the duration of the evaluated mini-epochs (2 vs. 3 s) and epochs (20 vs. 30 s) depending on historical national differences in polysomnographic recording paper speed, and the amplitude criterion with 4-times vs. 2-times the background EMG activity, as well as the duration of phasic EMG activity with 0.1–5 s vs. 0.1–10 s (for details, see [22]). The latest modification concerns the new introduction of the measure “any” in order to simplify the quantification of EMG activity during REM sleep, as the differentiation between phasic and tonic EMG activity can be challenging in clinical practice [21]. “Any” EMG activity is defined as presence of any EMG activity exceeding 0.1 s with an amplitude of twice the background EMG activity [21]. Apart from the Lapierre & Montplaisir scoring system, two different scoring approaches have been introduced [29–32]. Eisensehr et al. differentiated between short- and long-lasting EMG activity [29]: short-lasting EMG activity is defined as a minimum of 10 bursts of EMG activity between 0.1 and 0.5 s during a 10 s EEG epoch, and long-lasting EMG activity as >0.5 s activity for at least 1 s of the 10 s epoch [29]. Bliwise et al. [30] investigated the phasic electromyographic metric (PEM) which is defined as EMG activity exceeding 0.1 s with an identifiable return to baseline during the respective 2.5 s mini-epochs. In a recent study, the Mayo group introduced phasic burst duration as a new related measure [35]. Higher levels of phasic muscle activity even in nights without behavioral abnormalities have previously been described by Bliwise and Rye [33].
For further details see Table 11.2.
Table 11.2
Overview of studies which manually quantified REM sleep-related EMG activity
Authors | EMG measure | Amplitude | Duration (s) | Evaluated muscles | Epoch duration (s) |
|---|---|---|---|---|---|
Lapierre and Montplaisir [23] | Phasic | 4× background | 0.1–5 | Submental | 2 |
Tonic | N/A | >50 % of epoch | 20 | ||
Eisensehr et al. [29] | Short-lasting | 50 % amplitude increase | >10 × 0.1–0.5 | Mental, submental, TA | 10 |
Long-lasting | 50 % amplitude increase | >0.5 for >1 | |||
Consens et al. [24] | Phasic | >4× background | 0.1–5 | Chin | 3 |
Tonic | >4× background | 50 % of epoch | 30 | ||
PEM | >2× background | 0.1, identifiable return to baseline in the mini-epoch | Mental, brachioradialis, TA | 2.5 | |
Phasic | >4× background | 0.1–5 (total >5) | Chin, limbs | 30 | |
Tonic | > the minimum NREM amplitude | >50 % of epoch | 30 | ||
Zhang et al. [26] | Phasic | >4× background | 0.1–5 | Chin, extensor forearm, TA | 3 |
Tonic | >2× background | 50 % of epoch | 30 | ||
SINBAR (Frauscher et al. [25]) | Phasic | >2× background | 0.1–5 | Mental, SCM, deltoid, biceps, FDS, APB, TL paraspinal, RF, GAS, TA, EDB | 3 |
Montplaisir et al. [27] | Phasic | >4× background | 0.1–10 | Mental, TA | 2 |
Tonic | >2× background or 10 μV | >50 % of epoch | 20 | ||
SINBAR (Iranzo et al. [28]) | Phasic | >2× background | 0.1–5.0 s | Mental, FDS, EDB | 3 |
SINBAR (Frauscher et al. [21] | Phasic | >2× background | 0.1–5 | Mental, SCM, biceps, FDS, TA, EDB | 3 |
Tonic | >2× background or 10 μV | >50 % of epoch | 30 | ||
Any | >2× background | ≥0.1 | 3 | ||
McCarter et al. [33] | Phasic burst | >4× background | ≥0.1 | Chin, limbs | Single counts |
Phasic | >4× background | 0.1–14.9 s | 3 | ||
Any | >4× background | ≥0.1 | 3 | ||
Tonic | >2× background or 10 μV | >15 s | 30 |
Legend: PEM phasic electromyographic metric, TA tibialis anterior, SCM sternocleidomastoid, FDS flexor digitorum superficialis, APB abductor pollicis brevis, TL thoracolumbal, RF rectus femoris, GAS gastrocnemius, EDB extensor digitorum brevis
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