ORIGINAL ARTICLE J Sleep Med 2015;12(2):47-52 pissn 2384-2423 / eissn 2384-2431 http://dx.doi.org/10.13078/jsm.15009 Video Polysomnographic Analysis of Dream-Enacting Behaviors in the Patients with REM Sleep Behavior Disorder Jung Jun Park 1, Hyung Ji Kim 1, Jae Wook Cho 2, Jee Hyun Kim 1 1 Department of Neurology, Dankook University College of Medicine, Dankook University Hospital, Cheonan, 2 Department of Neurology, Pusan National University School of Medicine, Yangsan Hospital, Yangsan, Korea 수면다원검사 중 비디오 분석을 통한 렘수면행동장애를 가진 환자들의 꿈꾸면서 하는 행동들의 분석 박정준 1, 김형지 1, 조재욱 2, 김지현 1 단국대학교 의과대학 단국대학교병원 신경과, 1 부산대학교 의과대학 양산병원 신경과 2 Received October 26, 2015 Revised October 29, 2015 Accepted October 30, 2015 Address for correspondence Jee Hyun Kim, MD, PhD Department of Neurology, Dankook University College of Medicine, Dankook University Hospital, 201 Manghyang-ro, Dongnam-gu, Cheonan 31116, Korea Tel: +82-41-550-3292 Fax: +82-41-556-6245 E-mail: fever26@gmail.com Objectives: The aim of this study is to analyze dream-enacting behaviors (DEB) using video REM sleep behavior disorder severity scale (RBDSS) during night polysomnography (PSG) and compare them between in patients with idiopathic RBD (irbd) and patients with symptomatic RBD (srbd). Methods: 21 consecutive patients with either irbd or srbd were recruited (15 female and 10 male, mean age 63.6±13.86 years). Video analysis of DEB in all the REM sleep during their night PSGs was retrospectively performed using RBDSS. According to the clinical history depicting behaviors were also categorized by RBDSS-C to compare with the video RBDSS. Comparison of difference of RBDSS in between patients with irbd and in those with srbd was done. The frequency of DEB during the night PSG was measured as RBD density. Results: irbd patients had higher RBD density than srbd despite the same disease duration. irbd patients also tended to have higher RBDSS than srbd, compatible with higher prevalence of injury history. Night-night variability was observed in the patients comparing RBDSS and RBDSS-C. Conclusions: RBDSS is an easy tool to analyze severity of DEB in patients with RBD. Analysis of clinical feature of DEB may give a clue to differentiation of RBD patients as well as the alarm for the treatment of RBD to prevent potential injury. J Sleep Med 2015;12(2):47-52 Key Words: REM sleep behavior disorder, Video night polysomnography, Dream-enacting behavior, RBD severity scale, Injury. 렘수면행동장애는 렘수면동안수면을방해하거나 부상을유발할가능성이있는비정상적인행동이일어나는 이없어지고근전도가비정상적으로증가하여꿈에서하 수면장애다 렘수면에서관찰되는골격근의무긴장증- 는행동을자는동안에하게되는수면장애로사건수면- 으로분류된다 원인이될만한뇌병변이나동반 질환없이발생하는특발성렘수면행동장애 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. 가있고파킨슨증후군기면병이나다른뇌간의병변을 가진환자에서동반되는이차성또는증상성렘수면행동장 애로분류할수있 다 최근수년간환자들을추적한연구들은가 다발성신경계위축증이나루이소체치 매파킨슨씨병 과같은시누클레인병증을가진퇴행성뇌신경계질 환의전구증상임을밝히고있다 따라서파킨슨증상없 이먼저발생하였다가년이후에약의환자 들이위에서언급한파킨슨증후군으로진행하는임상경과 를보여퇴행성신경계질환의초기지표및비운동성증상으 로인식되고있다 렘수면행동장애에서관찰되는꿈을 꾸면서보이는행동들은다 Copyright 2015 Korean Sleep Research Society 47
Video Analysis of Dream-Enacting Behaviors in RBD Patients 양하다단순히누군가와대화하듯이중얼거리는잠꼬대에 서웃거나욕설을하거나누군가와싸우듯이소리지르고외 치는증상싸우거나쫓기는꿈과함께발로차는듯한행동 주먹으로때리는듯한행동과같은과격한행동을보이는경 우가흔하며손으로물건을만지는듯한약한행동이나드 물지만먹거나담배를피우는듯한행동을보이기도한다 렘수면행동장애의진단은수면다원검사에서렘수면중렘 수면무긴장소실과함께 임상병력이나검사중관찰된로진단을하게된다 를진단하기위해서는렘수면때증가한긴장성근전 도와위상성근전도를분석하게된다 최근 등이비디오야간수면다원검사에기록 된렘수면행동장애환자들이보이는다양한행동들을비교 적쉽게분석하는분류법을고안하여그를적용해보는연구 를시행하였고꿈꾸면서보이는행동들을정량화시키려는 시도가있었다 이연구에서는그들이고안한분석방법인렘 수면행동장애심각도척도- 로비교적간단하고쉽게정량화할수 있음을보여주었다이러한렘수면의임상행동을분석하려 는시도는렘수면행동장애를분류하거나진행여부를분석 하는데임상적인효용성이있을수있다 본연구에서는를이용하여수면다원검사시기록 된를비디오를분석하여분류해보고또한이분류방법 을임상병력에도적용하여비교해보고자하였다또한 및환자군간의양상이나심각도의차이가있는지 보고자하였다 년부터년까지단국대병원신경과에내원하여야 간수면다원검사를시행하여렘수면행동장애로진단받은환 자들을대상으로후향적으로분석하였다 모두국제수면장애분류판 의렘수면행동장애의진단기준에따 라진단이되었으며 원발성렘수면행동장애및파킨 슨증후군또는기면병과동반된증상성렘수면행동장애 를가진환자를포함시켜분석하였다또한동반된폐쇄성무 호흡장애의치료를위하여비강양압기적정압력을결정하 기위하여시행한수면다원검사도렘수면이기록되었다면분 석에포함시켰다모든환자들은렘수면행동장애를위한치 료약물이나중추신경계에작용하는약물을복용하지않고검 사를시행하였다단비강양압기검사를위한번째수면다원 검사를시행한환자중명은약물복용중에검사가이루어 졌다 본연구는의허가하에이루 어졌다 (ICSD-2) 수면다원검사에서렘수면에서의근육긴장도소실의부 재를확인한다턱근육근전도의지속적인또는간헐적인증 가또는턱근육또는팔다리에서의위상성근전도의증가 다음중적어도한가지의증상이있어야한다 수면중다친적이있거나위험한행동또는수면을방 해하는행동을보인병력 또는수면다원검사중렘수면에서비정상적인행동이 관찰된경우 임상양상이동반된렘수면관련뇌전증과임상적으로확 실히구분되는경우가아니라면뇌파에서경련파가없어야함 환자의수면장애가다른수면장애나내과적인질환신경 과정신과질환약물이나물질사용으로설명되지않아야한다 (Night polysomnography, PSG) 일반적인수면다원검사의절차에따라시행되었다단움 직임의관찰을위해양쪽팔의근위부와원위부에추가의 전극을부착하였다검사는단국대병원의수면검사실에서 하룻밤또는비강양압기를사용하는경우에는이틀밤동안 시행되었고첫번째검사와두번째검사를바로이어서시행 하지는않았다전극은뇌파를위한 및안전도턱근전도양측경골근및팔의근위부와원위부의 전극호흡을관찰하기위한 흉부와복부의호흡노력을보기위한벨트및자 세위치센서심전도산소포화도의센서를부착하였다 렘수면행동장애심각도척도를사용하여분석하였 고검사동안기록된모든렘수면중관찰된모든움직임을 비디오를통해분석하였다 분석은신경과의사일인 이시행하였다 분석은움직임과소리의두가지측면에서분석하여다음 과같이분류하였다 모든행동을분석하여가장높은점수를환자의로 택하였고움직임과소리로구분하여따로표시하였다 처 음숫자는움직임의척도이며두번째숫자는소리척도이다 비강양압기를사용한환자에서는두번의검사중가장높은 점수를택하였다는다음과같다 48
Park JJ et al. 움직임 움직임이없음 약간의움직임이나떨림 폭력적인행동을포함한근위부의팔다리의움직임 침대에서떨어지는것과같은몸의중앙부를이동하는 움직임축행동 소리 없음코골이는제외 소리를냄 렘수면중보인모든행동의숫자를전체렘수면시간으로 나누어렘수면행동의밀도밀도를구하 였다 DEB 환자의의무기록을조사하였으며렘수면행동장애의유병 기간현재까지로생긴부상의병력을조사하였다외 래진료기록을바탕으로환자및보호자가서술하는의 임상증상을바탕으로상기의를적용하여분류하였고 이는로표시하였다또한진단후렘수면행동장 애의치료로사용한약물을조사하였다 을이용하여분석 하였다와군의및밀도의비교를 위해서는를시행하였고인구학적정보 의분석을위해서는를시행하였다환자군 내의와를비교하기위해서 를시행하였다p<를통계적인유의성 이있는것으로간주하였다 총명의환자가연구에포함되었고남자가명이었으 며평균연령은±세세였다명의 환자와명의환자명의파킨슨증후군환자및명 의기면병환자가포함되었다평균년의유병기간을호 소하였고약에서로인한신체손상의병력을호 소하였다명중명의환자는비강양압기의압력을결정하 기위해번의수면다원검사를시행하여총개의수면다원 Table 1. Demographics of subjects n=21 Gender Male 10 Age (year±sd) 63.7±13.9 (15 79) Idiopathic RBD, no 15 Secondary RBD, no 6 No. of RBD episodes±sd 16.1±12.4 (1 40) Injury history, no (%) 9 (42.7) RBD: REM sleep behavior disorder 검사를분석하였다각환자들에서평균±회의 가기록되었다 RBDSS RBDSS-C 소리척도를비교하였을때는모두즉소리를 내었다고하였으나의환자에서는으 로소리가관찰되지않았다움직임의척도를비교하였을때 의환자에서와의차이가관찰 되었고그중는임상적으로수면다원검사보다더심한 움직임이보고되었고>는수면다원 검사에서더큰움직임이관찰되었다통계적으로도 유의한차이가관찰되었다± ±p 수면다원검사를시행한후에기면병환자명을제외한 명의환자들은모두약물을처방받았고클로나제팜외에멜 라토닌도함께복용하는환자들은명으로그중명이 환자였다 또한비강양압기의압력을결정하기위해한번더수면다 원검사를시행했던명의환자들의를비교했을때 명의환자에서기록하는날에따른의움직임척도 가일치하지않음을확인할수있었다그러나명 의환자는차수면다원검사와차검사간개월에서년이 상의시행시기의큰차이가있었고두번째검사에서약물을 복용하고시행하였으므로의날에따른변이를보기위 한통계분석을시행하지는않았다 irbd srbd RBDSS RBD 환자들의연령및의유병기간은두군간에비슷한반 면환자군에서환자군에비해밀도가의미 있게높았다±±p또한 도환자에서높은경향을보였다±± p는두군간에통계적으로유의하지 않았으나역시환자군에서환자보다높은경향 http://journal.sleepnet.or.kr 49
Video Analysis of Dream-Enacting Behaviors in RBD Patients 을보였고실제환자에서렘수면행동으로인한신체부 상의병력이의미있게더높았다p 렘수면동안증가된근전도의정량화를통한렘수면행동 장애의진단및임상적인연관성을알아보고자한연구들이 많이시행되어져왔다 파킨슨병환자의렘수면동안의근 육긴장도를분석한연구들에서는파킨슨병의아형이나성별 과긴장성근전도의증가와관련이있다고보고한것도있고 렘수면중근육긴장도의증가정도와파킨슨병증상의심각 도및유병기간이관련이있다고보고한연구도있으며 초 기환자의렘수면중근육긴장도의증가가높은군이 퇴행성신경계질환을보일가능성이높다고보고하였다 렘수면행동장애환자의비디오분석도시도되어왔었 으며 등은와군의임상양상은큰 차이가없다고보고하였다 기존연구들에서시행한비디오 분석방법은다소복잡하고시간이오래걸린다는단점이있 었다 년에 등이고안해낸렘수면행동장애의 Table 2. RBDSS based on PSG finding and clinical history of each patient No. Sex Age Type of RBD RBD duration (year) RBDSS RBDSS-C RBD density Medication 1 M 74 I 11 3.1 3.1 0.241 CNZ+MTN 2 F 65 S 2 1.0 1.1 0.022 CNZ 3* M 62 I 5 1.0 3.1 0.155 CNZ 4 F 66 I 13 2.1 2.1 0.072 CNZ+MTN 5* M 54 I 4 2.1 3.1 0.530 CNZ 6 M 15 S 5 3.1 3.1 0.091 None 7* F 53 I 13 3.1 2.1 0.370 CNZ+MTN 8* M 74 I 10 3.1 2.1 0.385 CNZ 9 M 66 I 3 2.1 2.1 0.525 CNZ 10* F 62 S 3 1.1 2.1 0.160 CNZ+MTN 11 F 64 I 3 2.1 2.1 0.274 CNZ 12* F 79 I 3 1.1 3.1 0.246 CNZ 13 M 74 S 2 1.1 1.1 0.125 CNZ 14* F 67 S 15 2.1 3.1 0.188 CNZ 15* F 72 I 5 1.1 3.1 0.336 CNZ+MTN 16 F 71 I 5 3.1 3.1 0.231 CNZ 17* F 47 S 3 0.1 1.1 0.195 CNZ 18* M 79 I 6 1.1 2.1 0.386 CNZ 19 M 58 I 4 2.0 2.1 0.400 CNZ 20 F 60 I 5 2.1 2.1 0.404 CNZ 21 M 73 I 4 1.1 1.1 0.636 CNZ *Patient who showed discrepancy of motor scale between RBDSS and RBDSS-C. RBD: REM sleep behavior disorder, I: idiopathic RBD, S: symptomatic RBD, RBDSS: RBD severity scale based on PSG recording, RBDSS-C: RBDSS based on clinical history, CNZ: clonazepam, MTN: melatonin, PSG: polysomnography Table 3. Night to night variability of RBD severity in the same patient Patient no. Age Interval between two PSGs (day) RBDSS RBD density Night 1 Night 2 Night 1 Night 2 1 74 120 3.1 1.1 0.24 0.11 2 65 50 1.0 2.1 0.02 0.21 3 62 2 1.0 1.0 0.16 0.02 4 66 1 2.1 2.1 0.07 0.08 5 54 480 2.1 3.1 0.53 0.71 RBD: REM sleep behavior disorder, RBDSS: RBD severity scale, PSG: polysomnography 50
Park JJ et al. Table 4. Comparison of RBDSS and RBD density between idiopathic RBD patients and symptomatic RBD patients 비디오수면다원검사분석을통한는비교적쉽게 꿈꾸면서보이는행동들을분류및정량화할수있고분석 기준이단순하여판독자간의일치도또한높은편이다 소 리와움직임의두측면으로이원화한점도편리하다본연구 에서는한명의신경과의사가수면다원검사중관찰되는모 든움직임을분석하였고임상병력에도적용하여및 로표시하여함께분석하여환자및 환자의를비교하였다 렘수면행동장애의심각도는크게두가지측면에서임상 적인의미가있을수있다첫째렘수면행동으로인한환자 나같이자는사람에게부상을일으킬만한잠재적인위험도 이다렘수면행동장애환자의에서자신이나함께잠 을자는사람의부상의병력이보고가되어있다 본연구 에서도의환자들에서부상의병력이있었다부상과 렘수면행동과관련된인자들에대한최근에시행된후향적 연구에서는환자가환자에비해부상의병력이 높으며함께자는사람보다는환자자신이다치는경향이많 다고보고하였다 의빈도는부상의병력과는크게관 계가없어빈도가많지않아도렘수면행동장애를치료해야 할필요성을강조하였다 본연구에서도와를 비교하였을때부상의병력이군에서의미있게높았다 두군은비슷한유병기간을가졌음에도군에서밀 도가의미있게더높아하룻밤에발생하는의빈도도 높았고또한가더높은경향을보여움직임이더컸 으므로군에서부상의병력이높은것을설명할수있 는소견이다본연구에서시행한것처럼수면다원검사시비 디오분석을통하여를분석하는것은특히함께자 는사람이없어정확한병력을알수없는환자의경우기록 하는날에따른변이가있을수있다는한계점이있긴하나 의임상양상및심한정도를객관적으로분석할수있 다는장점이있다와가일치하지않은것 은날에따른의운동증상의변이라고할수있으며 이는전체환자군의에서관찰되었다 irbd (SD) srbd (SD) p value No. 15 5 Age 67 (8.42) 63 (9.97) 0.553 RBD duration 6.26 (3.59) 5 (5.61) 0.098 RBD density 0.34 (0.13) 0.14 (0.07) 0.005 RBDSS (motor) 1.93 (0.79) 1 (0.7) 0.053 RBDSS-C (motor) 2.33 (0.61) 1.6 (0.89) 0.098 Injury history 60% 0% 0.019 RBD: REM sleep behavior disorder, RBDSS: RBD severity scale, RBDSS-C: RBD severity scale by clinical symptoms, irbd: idiopathic RBD, srbd: symptomatic RBD (the patient with narcolepsy excluded) 둘째를예후인자로사용할수있느냐는것이다 가시누클레인병증과관련된신경퇴행성질환의초기 생체징후일수있다는것은여러연구들에서밝혀졌고현재 의가장중요한임상적인의미일수있다 그러나 아직도환자에서로진행하는것을예측하는인 자는확실하게밝혀져있지않다등이시행한연구 에서환자에서로진행한환자의기존수면다원 검사를조사하였을때긴장성근전도의증가가진행하지않 은군에비해더증가되어있다고발표하여의정도 가예측인자일수있음을시사하였다 본연구에서는 와의를조사하였고단편적으로두군간의 의차이를보여주었다군의비디오수면다원 검사의추적관찰을통해외에도의비디오분석 이군에서도가높은환자에서더일찍파킨슨 증후군으로진행하게되는예후를예측할수있는생체신호 가될수있을지많은군의환자를통한추가분석이필요할 것이다 비디오분석을통한의분석은약물의치료전후를비 교하는데도움이될수있다를통하여 의치료효과를비교한연구에서는약물복용전후의수면다원 검사에서관찰된를로분석하여시행하였다 본연구의한계점은매우적은수의환자군을비교하였다 는점과병원에내원한환자를대상으로한연구였기때문 에선택편견이있을가능성을배제할수없다는점이다두 군간에서보여주는및밀도의차이가를 가진환자에서더높은것은실제로움직임이더크고폭력적 인행동이많아병원을일찍내원하게되었을가능성이높다 는점을고려해야한다또한분석당시환자들의의유 병기간이평균년으로시간경과후에군이 로진단이바뀔수있다는점이한계점이라고할수있다 는비록비디오를분석하여측정하는심각도척도 이나저자들이연구시이용한것처럼병력을가지고도분류 해볼수있다아주정확하지는않더라도지속적으로환자 http://journal.sleepnet.or.kr 51
Video Analysis of Dream-Enacting Behaviors in RBD Patients 를추적관찰하거나임상양상을정량화해볼수있다는점에 서유용할수있다그러나임상에서를이용시에빈 도는언급되어있지않은점이한계일수있다 저자들은는렘수면행동장애환자에서를정 량화할때또한의료진간의소통시도움이될것으로생각하 며초기관찰소견과추적관찰시소견과함께지속적 인연구를한다면의진행에대한정보를더제공할수 있을것으로생각한다또한움직임의분석은치료의 조기치료의필요성을강조할수있을것이다 REFERENCES 1. Schenck CH, Mahowald MW. REM sleep behavior disorder: clinical, developmental, and neuroscience perspectives 16 years after its formal identification in SLEEP. Sleep 2002;25:120-138. 2. Mahowald MW, Schenck CH, Bornemann MA. Pathophysiologic mechanisms in REM sleep behavior disorder. Curr Neurol Neurosci Rep 2007;7:167-172. 3. Arnulf I, Merino-Andreu M, Bloch F, et al. REM sleep behavior disorder and REM sleep without atonia in patients with progressive supranuclear palsy. Sleep 2005;28:349-354. 4. Cipolli C, Franceschini C, Mattarozzi K, Mazzetti M, Plazzi G. Overnight distribution and motor characteristics of REM sleep behaviour disorder episodes in patients with narcolepsy-cataplexy. Sleep Med 2011;12:635-640. 5. Schenck CH, Boeve BF. The strong presence of REM sleep behavior disorder in PD: clinical and research implications. Neurology 2011;77: 1030-1032. 6. Schenck CH, Boeve BF, Mahowald MW. Delayed emergence of a parkinsonian disorder or dementia in 81% of older men initially diagnosed with idiopathic rapid eye movement sleep behavior disorder: a 16-year update on a previously reported series. Sleep Med 2013;14:744-748. 7. Xi Z, Luning W. REM sleep behavior disorder in a patient with pontine stroke. Sleep Med 2009;10:143-146. 8. Boeve BF, Silber MH, Ferman TJ, et al. Clinicopathologic correlations in 172 cases of rapid eye movement sleep behavior disorder with or without a coexisting neurologic disorder. Sleep Med 2013;14:754-762. 9. Postuma RB, Gagnon JF, Montplaisir JY. REM sleep behavior disorder: from dreams to neurodegeneration. Neurobiol Dis 2012;46:553-558. 10. Schenck CH. Rapid eye movement sleep behavior disorder: current knowledge and future directions. Sleep Med 2013;14:699-702. 11. Dugger BN, Boeve BF, Murray ME, et al. Rapid eye movement sleep behavior disorder and subtypes in autopsy-confirmed dementia with Lewy bodies. Mov Disord 2012;27:72-78. 12. Boeve BF, Silber MH, Saper CB, et al. Pathophysiology of REM sleep behaviour disorder and relevance to neurodegenerative disease. Brain 2007;130(Pt 11):2770-2788. 13. Postuma RB, Lang AE, Gagnon JF, Pelletier A, Montplaisir JY. How does parkinsonism start? Prodromal parkinsonism motor changes in idiopathic REM sleep behaviour disorder. Brain 2012;135(Pt 6):1860-1870. 14. American Academy of Sleep Medicine. The international classification of sleep disorders: diagnostic and coding manual. 2nd ed. Westchester, IL: American Academy of Sleep Medicine, 2005;148-152. 15. Iber C, Ancoli-Israel S, Chesson AL, Quan SF. The AASM Manual for the Scoring of Sleep and Associated Events: Rules, Terminology, and Technical Specifications. 1st ed. Westchester, IL: American Academy of Sleep Medicine, 2007. 16. Sixel-Döring F, Schweitzer M, Mollenhauer B, Trenkwalder C. Intraindividual variability of REM sleep behavior disorder in Parkinson s disease: a comparative assessment using a new REM sleep behavior disorder severity scale (RBDSS) for clinical routine. J Clin Sleep Med 2011;7: 75-80. 17. Consens FB, Chervin RD, Koeppe RA, et al. Validation of a polysomnographic score for REM sleep behavior disorder. Sleep 2005;28:993-997. 18. Frauscher B, Iranzo A, Högl B, et al. Quantification of electromyographic activity during REM sleep in multiple muscles in REM sleep behavior disorder. Sleep 2008;31:724-731. 19. Frauscher B, Iranzo A, Gaig C, et al. Normative EMG values during REM sleep for the diagnosis of REM sleep behavior disorder. Sleep 2012; 35:835-847. 20. Park SG, Shin DJ, Park HM, Lee YB, Shin DH, Park KH. Diagnostic approach with quantitative anlysis of polysomnography in REM sleep behavior disorder. J Korean Sleep Res Soc 2012;9:46-51. 21. Lee SA, Kim CS, Cho CU, Kim B, Lee GH. Quantitative EMG criteria for diagnosing idiopathic REM sleep behavior disorder. Sleep Breath 2015;19:685-691. 22. Bliwise DL, Trotti LM, Greer SA, Juncos JJ, Rye DB. Phasic muscle activity in sleep and clinical features of Parkinson disease. Ann Neurol 2010;68:353-359. 23. Montplaisir J, Gagnon JF, Fantini ML, et al. Polysomnographic diagnosis of idiopathic REM sleep behavior disorder. Mov Disord 2010;25: 2044-2051. 24. Iranzo A, Ratti PL, Casanova-Molla J, Serradell M, Vilaseca I, Santamaria J. Excessive muscle activity increases over time in idiopathic REM sleep behavior disorder. Sleep 2009;32:1149-1153. 25. Chahine LM, Kauta SR, Daley JT, Cantor CR, Dahodwala N. Surface EMG activity during REM sleep in Parkinson s disease correlates with disease severity. Parkinsonism Relat Disord 2014;20:766-771. 26. Postuma RB, Gagnon JF, Rompré S, Montplaisir JY. Severity of REM atonia loss in idiopathic REM sleep behavior disorder predicts Parkinson disease. Neurology 2010;74:239-244. 27. Frauscher B, Gschliesser V, Brandauer E, et al. Video analysis of motor events in REM sleep behavior disorder. Mov Disord 2007;22:1464-1470. 28. Cygan F, Oudiette D, Leclair-Visonneau L, Leu-Semenescu S, Arnulf I. Night-to-night variability of muscle tone, movements, and vocalizations in patients with REM sleep behavior disorder. J Clin Sleep Med 2010;6:551-555. 29. Iranzo A, Santamaría J, Rye DB, et al. Characteristics of idiopathic REM sleep behavior disorder and that associated with MSA and PD. Neurology 2005;65:247-252. 30. Chiu HF, Wing YK, Lam LC, et al. Sleep-related injury in the elderly--an epidemiological study in Hong Kong. Sleep 2000;23:513-517. 31. McCarter SJ, St Louis EK, Boswell CL, et al. Factors associated with injury in REM sleep behavior disorder. Sleep Med 2014;15:1332-1338. 32. Ferri R, Marelli S, Ferini-Strambi L, et al. An observational clinical and video-polysomnographic study of the effects of clonazepam in REM sleep behavior disorder. Sleep Med 2013;14:24-29. 52