Sleep Medicine 13 (2012) 402–408

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Sleep Medicine

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Original Article

Sensations in restless legs syndrome

Elias Georges Karroum a,c,d, Jean-Louis Golmard b,c, Smaranda Leu-Semenescu a,c,d, Isabelle Arnulf a,c,d,⇑a Unité des Pathologies du Sommeil, Groupe Hospitalier Pitié-Salpêtrière, Paris, Franceb Unité de Biostatistiques et Information Médicale, Groupe Hospitalier Pitié-Salpêtrière, Paris, Francec Université Pierre et Marie Curie (UPMC, Paris 6), Paris, Franced Centre de Recherche de l’Institut du Cerveau et de la Moelle épinière (CRICM), UPMC/Inserm UMR_S975/CNRS UMR7225, Paris, France

a r t i c l e i n f o

Article history:Received 2 November 2010Received in revised form 19 December 2010Accepted 26 January 2011Available online 31 January 2012

Keywords:Restless legs syndromeSensationsDescriptorsQualifiersMcGill Pain QuestionnaireQuestion Douleur Saint-AntoineNeuropathic pain

1389-9457/$ - see front matter � 2011 Elsevier B.V. Adoi:10.1016/j.sleep.2011.01.021

⇑ Corresponding author at: Unité des Pathologies duPitié-Salpêtrière, 47-83 Boulevard de l’Hôpital, 75651+33 1 42 16 77 02; fax: +33 1 42 16 77 00.

E-mail addresses: isabelle.arnulf@psl.aphp.fr, isabe(I. Arnulf).

a b s t r a c t

Objective: To characterize the verbal descriptors of the sensations in restless legs syndrome (RLS) indepth.Methods: Fifty-six patients with primary RLS (interviewed in person) and 738 members of the French RLSAssociation (sent a postal questionnaire) were included in the study. Patients in the clinical series wereasked to report their RLS sensations in detail. The two groups completed a French reconstruction of theMcGill Pain Questionnaire (QDSA) to assess their RLS sensations.Results: All patients in both groups had abnormal sensations associated with the urge to move the legs. Mostpatients in the clinical series reported spontaneous ‘‘electrical,’’ ‘‘prickling,’’ ‘‘burning,’’ ‘‘tingling,’’ and ‘‘itch-ing’’ sensations. In the QDSA, more than two-thirds of subjects in both groups selected the sensory subclass-es ‘‘temporal’’ and ‘‘paresthesias,’’ and the affective subclasses ‘‘evaluative,’’ ‘‘nervous tension,’’ ‘‘asthenia,fatigue,’’ and ‘‘punishment.’’ More than one-third of subjects chose the sensory words ‘‘electric shocks,’’‘‘irradiating,’’ and ‘‘tingling,’’ and the affective words ‘‘exhausting,’’ ‘‘distressing,’’ ‘‘unbearable,’’ ‘‘irritating,’’and ‘‘depressing.’’ The subjects used more heat than cold descriptors to express their sensations.Conclusion: RLS is a primary sensory disorder without any pure motor form. The sensory descriptors in RLScould be similar to those of neuropathic pain, except for rare cold and numbness sensations.

� 2011 Elsevier B.V. All rights reserved.

1. Introduction irregular rhythm’’ [3]. However, patients with RLS can still report

Restless legs syndrome (RLS) is a neurological disorder classi-cally characterized by an urge to move the lower limbs. RLS symp-toms occur during inactivity, worsen during the evening and night,and are alleviated by moving the troublesome limbs [1]. The urgeto move the limbs is a subjective internal experience that is differ-ent from the voluntary motor restlessness (walking, stretching,flexing, or rubbing the legs) that usually follows. It is a necessarysymptom for the diagnosis of RLS. This focal akathisia is accompa-nied by abnormal sensations (especially paresthesia or dysesthe-sia-like sensations) of the same limbs in most patients [1,2].Patients with RLS find it very difficult to describe these sensations.Indeed, some patients merely report uncomfortable or unpleasantsensations that are simply indescribable [1,2]. Some patients usemetaphors such as ‘‘Elvis legs’’ or ‘‘soda bubbling in the veins’’[1], while others describe their sensations with complete sentencessuch as ‘‘it feels as though my whole legs were full of worms’’ or ‘‘itfelt as though something widened and contracted in a slow and

ll rights reserved.

Sommeil, Groupe HospitalierParis Cedex 13, France. Tel.:

lle.arnulf@psl.ap-hop-paris.fr

these sensations with simple verbal descriptors such as ‘‘crawling,’’‘‘tingling,’’ ‘‘pulling,’’ ‘‘stinging,’’ or ‘‘burning’’ [4,5]. Moreover, 47–61% of RLS patients [5–7] perceive these uncomfortable sensationsas painful. In two small sample studies, all RLS patients selectedverbal descriptors from the McGill Pain Questionnaire (MPQ) toassess their sensations [8,9], including the sensory descriptors:‘‘tingling,’’ ‘‘gnawing,’’ ‘‘jumping,’’ ‘‘pricking,’’ ‘‘dull,’’ and ‘‘aching’’[9]. Studies in RLS are seldom focused on these peculiar sensations.To date, no large study has been conducted to characterize the sen-sory component of the symptoms in RLS in more detail. Therefore,the aim of the current study was to investigate the verbal qualifiersof the sensations in RLS in depth, and to compare the qualifiersused in two groups: a clinical series of 56 patients with primaryRLS and a large sample of 738 subjects who were members ofthe French RLS Association.

2. Methods

2.1. Subjects and study design

2.1.1. Clinical series of patients with RLSPatients meeting the criteria for primary RLS [1] were selected

for inclusion in the study. The diagnosis of idiopathic RLS was

E.G. Karroum et al. / Sleep Medicine 13 (2012) 402–408 403

made by two neurologists experienced in sleep medicine and RLS(IA, SLS). Patients with RLS secondary to iron deficiency, renal fail-ure, pregnancy, side-effects of drugs, or neuropathy were excluded.Fifty-six patients with primary RLS who had been followed formore than five years at the sleep unit of the Pitié-Salpêtrière Hos-pital volunteered to participate and completed the study over a 1-year period. They signed an informed consent form, and the studywas approved by the hospital ethics committee. The patients wereinterviewed face to face by the same physician (EGK) using a semi-structured questionnaire.

2.1.2. Members of the RLS AssociationThe members of the French RLS Association (Association Franç-

aise des personnes affectées par le Syndrome des Jambes sans Re-pos [AFSJR]) were the target population. At the time of the study,the AFSJR had 2742 members (1814 females [66%]). Two thousandfive hundred members (91%) were selected at random and sent ananonymous structured questionnaire within a 20-day period, alongwith a letter explaining the aim of the study and how to return thequestionnaire. Four questions based on the four essential diagnos-tic criteria of the International Restless Legs Syndrome StudyGroup [1], translated into layman’s terms, were included in thequestionnaire, and were used to identify members affected withRLS. The questions were:

(1) Do you feel or have you ever felt an irresistible urge to moveyour legs?

(2) If you feel or you have ever felt an irresistible urge to moveyour legs, does it begin or become worse during periods ofrest or inactivity, such as sitting or lying down (in yourbed, on a plane, in the theater, etc.)?

(3) If you feel or you have ever felt an irresistible urge to moveyour legs, does it get better, at least partially, by movementssuch as walking or stretching your legs?

(4) If you feel or you have ever felt an irresistible urge to moveyour legs, does it begin or become worse during the eveningor the night?

A positive answer to all four questions was required for a pre-sumed diagnosis of RLS and inclusion in the study.

2.2. Measures

2.2.1. Measures performed in the clinical series and the AFSJR sampleSubjects in both groups completed a questionnaire including

questions on demographics (age and gender), general features ofRLS (age at onset; family history of RLS; reported involuntary legjerks while awake, especially during the evening and while asleepif reported by partners), treatment characteristics of RLS (history ofRLS treatment with dopaminergic agents [DA], positive responseunder DA, current treatment of RLS, current DA treatment), andgeneral questions on RLS sensations (presence of uncomfortablesensations associated with the urge to move the legs and if thesesensations were painful). All subjects completed the InternationalRestless Legs Severity Scale (IRLS), a validated [10] 10-item scalemeasuring the frequency, intensity, and impact of RLS symptomswith a five-point scale assessing each item (total score 0–40).The subjects also completed the ‘Questionnaire Douleur de Saint-Antoine’ (QDSA), a validated [11,12] French reconstruction of theMPQ [13]. The QDSA was designed using a similar methodologyas the MPQ, and its verbal descriptors were generated based onFrench translations of the MPQ, a review of the French medical lit-erature about the semiology of pain, and face-to-face interviewswith chronic pain patients [11]. The QDSA is composed of 58 painwords categorized into two classes (sensory or affective) and 16subclasses (1–9 sensory and 10–16 affective), while the MPQ is

composed of 78 pain descriptors categorized in four classes (sen-sory, affective, evaluative, and miscellaneous) and 20 subclasses(1–10 sensory, 10–15 affective, 16 evaluative, and 17–20 miscella-neous). The two pain questionnaires have 35 descriptors in com-mon, and 68% of these words are categorized in equivalentsubclasses. Direct translations of the MPQ in French Canadian havebeen compared with the QDSA, leading to the recommendationthat the QDSA version be used in France [12]. Each subclass inthe QDSA contains two to six verbal descriptors with a similarsemantic meaning but differing intensity, and classified accord-ingly. In each subclass of the QDSA, the subject chooses the wordthat best characterizes their sensations, with the option of notselecting any word in a particular subclass. They also give an inten-sity score ranging from zero to four for each chosen word. In addi-tion to qualitative information, the QDSA gives four types ofquantitative data: the number of words chosen by each subject(ranging from zero to 16) and three pain-rating indexes (PRI).PRI-S is the sum of the mean scale values (obtained by Boureauet al. [11]) of all the words chosen by the patient. PRI-R is thesum of the rank values (each word is given a rank value in its par-ticular subclass) of all the words chosen by the patient. The num-ber of words chosen, the PRI-S, and the PRI-R can also be generatedfrom the MPQ. Finally, PRI-P is the sum of the intensity scale values(ranging from zero to four) ascribed by the patient for each se-lected word at the time of investigation. This is specific to theQDSA; a global five-point intensity scale, the Present Pain Intensity,is generated in the MPQ. The correlation of each of these fourscores with the IRLS was measured for the patients in the clinicalseries and the AFSJR sample. French verbal descriptors (reportedor chosen from the QDSA) are presented with their most appropri-ate English equivalents in the ‘‘Results’’ section, although theremay be some semantic differences between the two languages.

2.2.2. Specific measures in the clinical seriesThe patients in the clinical series were also asked more detailed

questions about the uncomfortable sensations (frequency of occur-rence of the urge to move the legs: always, sometimes, and never)and their temporal relationship with the urge to move the legs (ifthe sensations occurred before, concomitantly with, or after theurge to move the legs). In addition, they were asked to give an ex-act description of their RLS sensations (exact verbatim) at thebeginning of the interview and before completing subsequentscales (IRLS and QDSA). The minimum number of the most sensi-tive reported sensory words covering the maximum number of pa-tients in the clinical series was obtained.

2.3. Statistical analysis

Quantitative data are presented as mean ± standard deviation,and categorical data as frequency and/or percentage. For the anal-ysis of quantitative data, the Student’s t-test was used to comparetwo independent groups. For the analysis of categorical data, theChi-squared test was used to compare two independent groups(Fisher’s exact test was used when at least one ‘‘expected’’ fre-quency was less than five). Bonferroni’s correction was appliedfor the comparison of multiple variables between groups (33 vari-ables with a corrected alpha error of 0.05/33 = 0.0015). The mini-mum number of the most sensitive reported sensory wordscovering the maximum number of patients in the clinical serieswas obtained using a step-wise method, beginning with the mostcommonly reported word and shifting downwards to the nextmost sensitive word (that covers the largest number of patientsnot covered by the previous selected word). When two wordshad the same sensitivity, the most commonly reported word wasselected. In this stepwise method, the sensory words reportedspontaneously were analyzed rather than the sensory words

404 E.G. Karroum et al. / Sleep Medicine 13 (2012) 402–408

chosen in the QDSA, because it was assumed that they would bemore accurate and closer to the exact RLS sensations. Spearman’srank correlation coefficient (q) was used to measure the strengthof the linear association between each of the four scores calculatedfrom the QDSA and the IRLS. All statistical tests were two-tailed.Computations were performed using SAS Version 9, except forthe step-wise method, which was performed by hand.

3. Results

Of the 2500 questionnaires sent to members of the AFSJR, 1203were returned (response rate 48%). Of those, only those subjectswho gave an affirmative answer to all four questions related tothe criteria of the International Restless Legs Syndrome StudyGroup for the diagnosis of RLS, and who completed the IRLS andthe QDSA correctly, were selected. As such, statistical analyseswere performed on the data of 738 members (61% of responders,29% of members who received a questionnaire). Most question-naires that were excluded from the analysis contained an incor-rectly completed QDSA.

3.1. General features of the clinical series and the AFSJR sample

The demographics, general features of RLS, treatment character-istics of RLS, general RLS sensations and IRLS, score for the patientsin the clinical series and the AFSJR sample are summarized in Ta-ble 1. The subjects in the AFSJR sample were less likely to have afamily history of RLS (p = 0.0013), had a higher IRLS score(p < 0.0001), and were less often being currently treated for RLS(p = 0.0003) compared with the patients in the clinical series. Therewere no other significant differences between the two groups interms of demographics and general RLS features.

3.2. Additional features of RLS sensations in the clinical series

In the clinical series, 54 (96%) patients complained of uncom-fortable sensations associated with the urge to move the legs.These uncomfortable sensations were always present in 47 (84%)patients and sometimes present in seven (12%) patients. The twopatients who never had uncomfortable sensations in their legsnoted peculiar sensations just before the urge to move the legs(heaviness in the legs with nervousness in one patient, and a verystressful situation with something moving from the tibia to theankles and feet in the other patient). Of the 54 patients with

Table 1General features of restless legs syndrome (RLS) subjects in the clinical series compared wiRepos (AFSJR) sample.

Number of subjects Cli

56

Age 64Gender (females) 37Age at RLS onset 37Family history of RLS 38Reported involuntary leg jerks while awake 43Reported involuntary leg jerks while asleep 40RLS treated before with DA 53Positive response under DA 53RLS currently treated 56RLS currently treated with DA 46Uncomfortable sensations associated with the urge to move 54Painful sensations associated with the urge to move 34IRLS score (0–40) 21

DA, dopaminergic agents; IRLS, International Restless Legs Severity Scale.Quantitative data are displayed as mean ± standard deviation, and categorical data are d* p < 0.0015 was considered significant because of multiple testing.

uncomfortable sensations, 30 (55%) experienced these sensationsexclusively before the urge to move the legs (and felt that thesensations triggered the urge to move the legs), while 20 (37%)patients could not separate the urge to move the legs from theseuncomfortable sensations. Three (6%) patients described thesesensations as occurring before and concomitantly with the urgeto move the legs, and only one (2%) patient had uncomfortablesensations after the urge to move the legs but also concomitantlywith the urge to move the legs.

3.3. Reported verbal descriptors by patients in the clinical series

The patients found it difficult to describe the quality of their sen-sations. They often used analogies (Appendix 1, online) and emo-tional or affective words such as ‘‘irritating,’’ ‘‘annoying,’’ and‘‘unbearable’’ (Table 2). They also often gave impressions of their sit-uation: ‘‘It is a disease from which we do not die but it prevents usfrom living’’; ‘‘It is as if I was punished from staying still and doingnothing’’; ‘‘The sensations begin as soon as I think of them’’; ‘‘Itmakes me aware of my legs’’; and ‘‘I have the nerves on edge.’’ Threepatients could not describe their symptoms with any specific sen-sory qualifier. (Two patients considered RLS sensations to be painfulin general, and another patients was just irritated by the sensa-tions.) However, the majority of patients (95%) could report sensoryverbal descriptors (Table 2), with a mean of 2.5 ± 1.7 words per pa-tient (range 0–8, median 2) and a total of 34 different sensory words.Common sensory descriptors (reported by at least 10% of patients)were ‘‘electrical,’’ ‘‘prickling,’’ ‘‘burning,’’ ‘‘tingling,’’ and ‘‘itching.’’At least one of these five sensory descriptors was reported by 41(73%) patients. When analyzing all the sensory words to find theminimum number of the most sensitive reported words coveringthe maximum number of patients (beginning with the most com-mon word: ‘‘electrical’’), three of the most common sensory words(‘‘electrical,’’ ‘‘tingling,’’ and ‘‘burning’’) covered 70% of all the pa-tients (when the word ‘‘tenseness’’ was included, this covered 75%of the patients), while 16 words (Fig. 1) covered 95% of the patientsreporting sensory words (15 words when eliminating the word‘‘stabbing’’ or ‘‘diffusing’’; each reported by only 4% of patients).

3.4. QDSA results from the clinical series and the AFSJR sample

The mean number of total words chosen from the QDSA per pa-tient was 9.7 ± 2.9 words (range 4–16, median 9.5) in the clinicalseries and 10.2 ± 3.6 words (range 1–16, median 10.5) in the AFSJR

th the Association Française des personnes affectées par le Syndrome des Jambes sans

nical series AFSJR sample

738 Response rate

.1 ± 11.3 65.7 ± 11.8 738 (100%)(66%) 457 (62%) 738 (100%)

.9 ± 16.8 42.3 ± 18.4 695 (94%)(68%) 313 (45%)* 688 (93%)(77%) 574 (78%) 732 (99%)(71%) 387 (62%) 625 (85%)(95%) 541 (89%) 611 (83%)(100%) 514 (95%) 541 (100%)(100%) 591 (81%)* 734 (99%)(82%) 476 (81%) 591 (100%)(96%) 716 (97%) 738 (100%)(61%) 407 (55%) 734 (99%)

.0 ± 9.4 26.9 ± 6.3* 738 (100%)

isplayed as frequency (%).

Table 2Reported verbal descriptors for the restless legs syndrome sensations (n = 56patients).

French descriptors English translation Percentage (frequency)Descriptifs sensoriels Sensory descriptors 95% (53)

Electriques Electrical 43% (24)Picotements Prickling 30% (17)Brûlure Burning 29% (16)Fourmillement Tingling 27% (15)Démangeaisons Itching 14% (8)Contraction Contraction 9% (5)Lourdeur Heaviness 7% (4)Pression Pressure 7% (4)Tension Tenseness 7% (4)Tiraillement Tugging 7% (4)Chaleur Heat 5% (3)Courbatures Aching 5% (3)Coup de poignard Stabbing 4% (2)Crispation Contortion 4% (2)Diffusante Diffusing 4% (2)Elancement Shooting 4% (2)En étau Squeezing 4% (2)Engourdissement Numbness 4% (2)Etirement Stretching 4% (2)Grattement Scratching 4% (2)Piqûre Pricking 4% (2)Serrement Tightness 4% (2)Arrachement Wrenching 2% (1)Broiement Grinding 2% (1)Chatouillement Tickling 2% (1)Constriction Constriction 2% (1)Dilatation Dilatation 2% (1)Elongation Elongation 2% (1)Etranglement Strangulation 2% (1)Froid Douloureux Painful cold 2% (1)Pincement Pinching 2% (1)Sourde Dull 2% (1)Torsion Twisting 2% (1)Vibrations Vibrating 2% (1)

Descriptifs affectifs Affective descriptors 41% (23)Enervante Irritating 18% (10)Agaçante Annoying 11% (6)Insupportable Unbearable 11% (6)Exaspérante Exasperating 2% (1)Gênante Awkward 2% (1)Irrépressible Irrepressible 2% (1)Malaise Discomfort 2% (1)Obsédante Obsessing 2% (1)Pénible Distressing 2% (1)Torturante Torturing 2% (1)

E.G. Karroum et al. / Sleep Medicine 13 (2012) 402–408 405

sample. The mean number of sensory words chosen from the QDSAper patient was 5.0 ± 1.9 words (range 1–9, median 5) in the clin-ical series and 5.3 ± 2.4 words (range 1–9, median 5) in the AFSJRsample. The PRI-S, PRI-R, and PRI-P scores were 24.7 ± 8.6,23.6 ± 9.0, and 25.2 ± 12.2, respectively, in the clinical series, and26.0 ± 10.0, 24.4 ± 10.0, and 30.5 ± 13.1, respectively, in the AFSJRsample. There were no significant differences between the twogroups for these four QDSA scores; the PRI-P of the AFSJR samplewas higher than that for the clinical series (p = 0.0027), but thiswas not statistically significant after applying Bonferroni’s correc-tion (p < 0.0015) for multiple testing. The overall choice of the pa-tients in the clinical series covered 55 (95%) words of the QDSA (32sensory descriptors out of 35 and 23 affective descriptors), whilethe subjects in the AFSJR sample chose all the words in the QDSA.In the clinical series, even the patients who only had abnormal sen-sations (i.e., not uncomfortable) and those who could not reportany simple verbal descriptors found the words in the QDSA veryadequate for assessing of their sensations. In the AFSJR sample,the 22 subjects with no uncomfortable sensations associated withthe urge to move the legs also chose a variety of words from theQDSA. In the two groups, more than two-thirds of the subjects

selected verbal descriptors from the sensory subclasses ‘‘temporal’’and ‘‘paresthesias,’’ and from the affective subclasses ‘‘evaluative,’’‘‘nervous tension,’’ ‘‘asthenia, fatigue,’’ and ‘‘punishment’’ (Tables3a and 3b). The sensory subclass ‘‘thermal cold’’ and the affectivesubclass ‘‘autonomic reactions’’ were chosen by less than one-thirdof patients. The frequency of choice of each subclass and the distri-bution of words chosen in each subclass were statistically similarbetween the two groups. Eight verbal descriptors were chosen fre-quently by more than one-third of the subjects in both groups:‘‘electric shocks,’’ ‘‘irradiating,’’ ‘‘tingling,’’ ‘‘exhausting,’’ ‘‘distress-ing,’’ ‘‘unbearable,’’ ‘‘irritating,’’ and ‘‘depressing.’’ In the clinicalseries, a moderate but significant correlation (q = 0.37, p = 0.005)was found between the IRLS and the PRI-P, but not between theIRLS and the number of chosen words, or the PRI-S and the PRI-R. However, in the AFSJR sample, the number of chosen wordsand the PRI-S, PRI-R, and PRI-P increased when the IRLS increased(p < 0.0001), and the PRI-P had the strongest (although still moder-ate) correlation (q = 0.56) with the IRLS (Appendix 2, online).

4. Discussion

This study of 56 patients with primary RLS (all treated) and 738members of an RLS Association (81% treated) explored the sensorycomponent of RLS symptoms quantitatively and qualitatively.

4.1. Does a pure motor form of RLS exist?

In the clinical series, all patients had abnormal sensations asso-ciated with the urge to move the legs that were mostly uncomfort-able (96%) and often occurred before (63%) or concomitantly (43%)with the urge to move the legs. These temporal patterns were re-ported recently with even higher frequencies in a small group ofpatients (n = 21) with RLS [14]. In addition, 95% of the patients inthe clinical series reported sensory verbal descriptors, and all thesubjects in both groups, including those without uncomfortablesensations, chose sensory descriptors from the QDSA. These find-ings challenge the existence of a ‘‘pure urge to move the legs’’ (puremotor form of RLS) that was reported previously [1,15] in approx-imately 10–20% of subjects with RLS [1].

4.2. Can the QDSA assess the RLS sensations accurately?

Of the 34 sensory words reported by the patients in the clinicalseries, 21 (62%) can be found in the QDSA. In addition, all the pa-tients in both groups selected sensory and affective words fromthe QDSA. Moreover, a moderate positive correlation was foundbetween the PRI-P of the QDSA and the general RLS severity scorefor both groups. These results suggest that the QDSA is a useful toolfor assessment of the sensations in RLS, as reported previously [9].However, 13 (38%) reported words were only semantically relatedto, or were distinct from, words in the QDSA. In addition, althoughRLS sensations (particularly painful sensations) are considered tobe one of the most troublesome symptoms by subjects with severeRLS [16,17], they are not evaluated by the IRLS (the gold-standardscale for measuring the severity of RLS in clinical practice and drugtrials), which mainly assesses the motor symptoms of RLS and itsimpact on sleep and quality of life. Therefore, a more sensitiveand specific scale that focuses on RLS sensations needs to be devel-oped to complement the IRLS.

4.3. The diverse RLS sensations: a neuropathic pain manifestation?

The patients in the clinical series reported a total of 34 sensorywords, and chose 32 sensory words out of 35 from the QDSA. Incontrast, the subjects in the AFSJR sample chose all the 35 sensory

Fig. 1. Cumulative frequency of patients (displayed as percentages) in the clinical series (n = 56) covered by the minimum number of sensitive sensory words, beginning withthe most commonly reported word (‘‘electrical’’). The number of patients exclusively covered by each word is displayed in parentheses after each word.

406 E.G. Karroum et al. / Sleep Medicine 13 (2012) 402–408

words in the QDSA. This resulted in the generation of a large vari-ety of sensory qualifiers describing RLS sensations (48 differentsensory words for the patients in the clinical series following elim-ination of duplicates). This diversity of RLS sensory descriptors maysuggest that the disorder is heterogeneous, with different sensoryphenotypes. Alternatively, the mechanism of RLS may involve acentral system modulating (rather than generating) the limb sen-sations, thereby creating diverse sensory symptoms.

The most commonly reported sensory descriptors (14–43% ofthe patients) in the clinical series (‘‘electrical,’’ ‘‘prickling,’’ ‘‘burn-ing,’’ ‘‘tingling,’’ and ‘‘itching’’) correspond to those characterizingneuropathic pain [18], and are typically used in validated neuro-pathic pain screening tools [19]. In addition, these five sensorydescriptors are part of the seven sensory qualifiers in the DN4, aFrench validated screening tool for neuropathic pain [20]. Three ofthese descriptors (‘‘electrical,’’ ‘‘tingling,’’ and ‘‘burning’’) coveredthe sensations in 70% of the patients in the clinical series; hencethey have good sensitivity. However, the last two DN4 words, ‘‘pain-ful cold’’ and ‘‘numbness’’ (chosen by 26% and 66% of neuropathicpain patients, respectively [20]), were rarely reported by the pa-tients in the clinical series (2% and 4%, respectively). Moreover, pa-tients in the clinical series and the AFSJR sample chose sensorywords from the subclasses ‘‘temporal’’ (mostly ‘‘electric shocks’’)and ‘‘paresthesias’’ (mostly ‘‘tingling’’), typically found in neuro-pathic pain groups, more often. However, they also often chosethe words ‘‘irradiating’’ and ‘‘hot,’’ which may not belong to the neu-ropathic pain spectrum (although ‘‘hot’’ is close to ‘‘burning,’’ foundin neuropathic pain). Controlled studies of patients with primaryRLS and patients with neuropathic pain are needed to determinewhether RLS sensations are similar to or distinct from neuropathicpain sensations by identifying distinct clustering of verbal descrip-tors, as undertaken previously for various chronic pain syndromes[18,21–23]. Similarly, one may compare the sensory qualifiers ofRLS sensations with those of other leg discomforts that are oftenconfused with RLS [24], including venous insufficiency, leg cramps,osteoarthritis, disc lesion injury, and intermittent claudication[17,25,26]. A cluster of specific sensory descriptors could improvethe specificity of a diagnosis of RLS (82–84% if based solely on thefour essential criteria for the diagnosis of RLS [27,28]) in future epi-demiological studies and in clinical practice.

The patients in the clinical series reported heat descriptors moreoften than cold descriptors to express their sensations. Similar re-sults were found comparing the subclasses ‘‘thermal hot’’ and ‘‘ther-mal cold’’ of the QDSA between the two groups (‘‘thermal hot’’ waschosen three times more than ‘‘thermal cold’’ in the AFSJR sampleand seven times more in the patients in the clinical series). Indeed,

patients with RLS often complain of the aggravating effect of a hotenvironment (e.g., summer season, blanket on the legs) on theirRLS symptoms compared with a cold environment. In the authors’experience, patients often position their feet and legs out of theblanket during the night, use refreshing creams, run cold showerson their legs, and walk on a cold floor to alleviate their symptoms.Although this suggests that the balance between cold and warmsensations would be abnormally switched towards warm, the pa-tients with primary RLS (unlike those with RLS secondary to smallfiber neuropathy) have normal thresholds for warm and cold (andcold and hot pain) sensations on quantitative sensory testing [29].

For the affective evaluation of the sensations, it is noteworthythat patients in the clinical series often reported the word ‘‘unbear-able.’’ In addition, in both groups, the subjects chose the words‘‘unbearable’’ and ‘‘distressing’’ much more often than the words‘‘awkward’’ and ‘‘unpleasant’’ from the subclass ‘‘evaluative’’ ofthe QDSA. These results contrast with the definition of RLS, usuallypresented as ‘‘unpleasant or uncomfortable sensations.’’ Here thepatients’ evaluation of the sensations is skewed towards a more se-vere affective description.

4.4. Limitations of the study

This study has some limitations that must be considered wheninterpreting the results. In the AFSJR sample, one cannot be surethat all members had true RLS. The authors attempted to reducefalse-positive results in the AFSJR sample by strictly applying theessential criteria for a diagnosis of RLS [1]. RLS mimics [27,28] suchas leg cramps, positional discomfort, and leg movements due to ha-bit or anxiety were not specifically excluded by adding additionalappropriate questions to the questionnaire. However, the fact thatthe sampling was made from an RLS Association and not from thegeneral population may have reduced this selection bias. Moreover,most RLS features were similar between the AFSJR sample and theclinical series, suggesting that the subjects in the AFSJR sample havetrue RLS. Another weakness of the study is that the IRLS was admin-istered to the AFSJR sample by mail, while it has been validated forface-to-face interview [10]. This could explain the lower IRLS scorefor the clinical series (the scale was completed during a face-to-faceinterview at the medical center in charge of the patient) comparedwith the AFSJR sample (the scale was self-completed by the AFSJRmembers). Similar concerns may apply to the QDSA since this painquestionnaire was validated in a face-to-face interview in the origi-nal study [11]. To circumvent this bias, 39% of the questionnaireswere excluded, mainly because of an incorrectly completed QDSA.Other limitations in the AFSJR sample are the low response rate

Table 3aDistribution (displayed as percentages) of verbal descriptors in each sensory subclassof the Questionnaire Douleur de Saint-Antoine (QDSA) as chosen by patients in therestless legs syndrome (RLS) clinical series compared with the Association Françaisedes personnes affectées par le Syndrome des Jambes sans Repos (AFSJR) sample.

QDSASensorysubclassesSensorydescriptors

Englishtranslation

Clinical series(n = 56) (%)

AFSJR sample(n = 738) (%)

Temporelle Temporal 81 87Battements Beating 0 2Pulsations Pulsing 2 5Elancements Shooting 25 29En éclairs Flashing 4 2Décharges électriques Electric

shocks50 48

Coups de marteau Pounding 0 1

Spatiale Spatial 64 59Rayonnante Radiating 9 11Irradiante Irradiating 55 48

Piqûre–Coupure Punctuate-incisive

50 64

Piqûre Pricking 7 9Coupure Cutting 0 0*

Pénétrante Penetrating 23 30Transperçante Piercing 13 16Coups de poignard Stabbing 7 9

Compression–Constriction

Constrictive 59 54

Pincement Pinching 2 7Serrement Tightness 18 13Compression Compressing 23 17Écrasement Crushing 2 2En étau Squeezing 9 11Broiement Grinding 5 4

Distension–Traction Traction 63 62Tiraillement Tugging 27 27Étirement Stretching 13 10Distension Distension 4 4Déchirure Tearing 4 3Torsion Twisting 13 15Arrachement Wrenching 2 3

Thermique: Chaud Thermal hot 59 59Chaleur Hot 32 33Brûlure Burning 27 26

Thermique: Froid Thermalcold

8 18

Froid Cold 4 14Glace Ice 4 4

Paresthésies Paresthesias 73 71Picotements Prickling 21 11Fourmillements Tingling 36 52Démangeaisons Itching 16 8

Caractère sourd Dullness 50 53Engourdissement Numbness 9 17Lourdeur Heaviness 21 19Sourde Dull 20 17

The QDSA is the French adapted version of the McGill Pain Questionnaire.* Only one subject chose the word ‘cutting’ in the AFSJR sample.

Table 3bDistribution (displayed as percentages) of verbal descriptors in each affective subclassof the Questionnaire Douleur de Saint-Antoine (QDSA) as chosen by patients in therestless legs syndrome (RLS) clinical series compared with the Association Françaisedes personnes affectées par le Syndrome des Jambes sans Repos (AFSJR) sample.

QDSAAffectivesubclassesAffectivedescriptors

Englishtranslation

Clinical series(n = 56) (%)

AFSJR sample(n = 738) (%)

Fatigue–Asthénie Asthenia,fatigue

86 89

Fatigante Tiring 32 32Epuisante Exhausting 36 42Éreintante Backbreaking 18 15

Réactions neuro-végétatives

Autonomicreactions

12 27

Nauséeuse Nauseating 5 14Suffocante Suffocating 2 9Syncopale Fainting 5 4

Anxiété Anxiety 55 61Inquiétante Disturbing 2 10Oppressante Oppressing 30 24Angoissante Frightening 23 27

Punition-Persécution Punishment 78 77Harcelante Harassing 18 21Obsédante Obsessing 29 25Cruelle Cruel 2 1Torturante Torturing 25 22Suppliciante Killing 4 8

Evaluation Gêne-Tolérance

Evaluative 98 97

Gênante Awkward 5 5Désagréable Unpleasant 7 11Pénible Distressing 38 35Insupportable Unbearable 48 46

Tension nerveuse Nervoustension

90 84

Énervante Irritating 43 35Exaspérante Exasperating 29 32Horripilante Maddening 18 17

Dépression Depression 46 60Déprimante Depressing 39 51Suicidaire Suicidal 7 9

The QDSA is the French adapted version of the McGill Pain Questionnaire.

E.G. Karroum et al. / Sleep Medicine 13 (2012) 402–408 407

and the fact that the authors could not distinguish between primaryand secondary RLS. In fact, the significantly lower family history inthe AFSJR sample may indicate that there was an increased numberof individuals in that sample with secondary RLS. Finally, bothgroups were mainly composed of subjects with severe RLS (almostall treated), which is different from general-population-based sam-ples. Although there were no significant differences between trea-ted and untreated subjects in the AFSJR sample in terms of thedistribution of words chosen from the QDSA, this study did notexamine sensations before and after treatment in the same sub-jects; therefore, an effect of RLS treatment on the quality of thesesensations cannot be ruled out.

5. Conclusion

This study of sensations in RLS, conducted in two large groups ofsubjects, documents RLS as a primary sensory disorder. No puremotor form of RLS was identified. The sensory descriptors of thesensations in RLS could be similar to those described in neuropathicpain. The emotional component of these sensations is skewedtowards words that describe a severe impact. These verbal descrip-tors can be used to develop a specific sensory questionnaire, whichwill better capture the patient experience and impact of treatments.

Conflict of interest

The ICMJE Uniform Disclosure Form for Potential Conflict ofinterest associated with this article can be viewed by clicking onthe following link: doi:10.1016/j.sleep.2011.01.021.

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