Brain Research Bulletin 70 (2006) 386–390 Olfactory deficit in idiopathic rapid eye movements sleep behavior disorder Maria Livia Fantini a,∗ , Ronald B. Postuma b , Jacques Montplaisir b,c , Luigi Ferini-Strambi a a Sleep Disorders Center, Department of Neurology, Universit` a Vita-Salute San Raffaele, Via Stamira d’Ancona n. 20, 20127 Milan, Italy b Centre d’´ etude du sommeil et des rythmes biologiques, H ˆ opital du Sacr´ e-Cœur de Montr´ eal, Montr´ eal, Qu´ ebec, Canada H4J 1C5 c D´ epartement de Psychiatrie, Universit´ e de Montr´ eal, Montr´ eal, Qu´ ebec, Canada H4J 1C5 Received 17 February 2006; received in revised form 14 July 2006; accepted 17 July 2006 Available online 7 August 2006 Abstract Introduction: REM sleep behavior disorder (RBD) is a parasomnia characterized by a loss of atonia and an increased phasic muscle activity during REM sleep. Idiopathic RBD frequently herald an alpha-synucleinopathy, including such as Parkinson’s disease (PD) and dementia with Lewy Body (DLB). Pathological changes in the anterior olfactory nucleus and olfactory loss occur very early in the course of PD and DLB. The aim of the study was to assess olfactory function in a large group of idiopathic RBD patients. Methods: Fifty-four consecutive polysomnographically-confirmed iRBD patients (44 men, 10 women; mean age: 69.2 ± 8.3 years; mean Unified Parkinson’s Disease Rating Scale Part III (UPDRS-III) score: 4.9 ± 4.3) and 54 age and gender-matched control subjects underwent the Brief University of Pennsylvania Smell Identification Test (B-SIT). Results: A marked olfactory impairment was observed in the RBD group (mean B-SIT score: 7.1 ± 2.5 versus 9.4 ± 1.8; p < 0.0001), with 33 (61.1%) RBD patients versus 9 (16.6%) controls showing abnormal olfactory function (p < 0.0001). No correlation was found between the degree of olfactory loss and either duration of RBD symptoms or UPDRS-III score. Deficit in recognize paint thinner odorant showed the highest positive predictive value (0.95) for identifying idiopathic RBD. Conclusions: The olfactory deficit found in most idiopathic RBD patients shares similarities with that described in PD and may be a sign of a widespread neurodegenerative process. Its detection may help in identifying subjects at higher risk of developing an alpha-synucleinopathy-mediated neurodegeneration. © 2006 Elsevier Inc. All rights reserved. Keywords: REM sleep behavior disorder; Olfaction; Lewy body disease 1. Introduction Rapid eye movement (REM) sleep behavior disorder (RBD) is characterized by a loss of the normal muscle atonia that accompanies REM sleep [21]. Patients show excessive motor activity usually associated with dreams that are rich in aggres- sive imagery [12]. The pathogenesis of RBD is partly known. It has been suggested that lesions of specific areas in the meso- pontine tegmentum and medial medulla are responsible [18,28], although an impairment of meso-striatal dopaminergic neurons has also been proposed [1,10]. ∗ Corresponding author. Tel.: +39 02 2643 3201; fax: +39 02 2643 3394. E-mail address: fantini.marialivia@hsr.it (M.L. Fantini). RBD is commonly associated with neurodegenerative disor- ders that are characterized by -synuclein deposition (synucle- inopathy), including Parkinson’s disease (PD), multiple system atrophy (MSA) and Lewy Body Dementia [4,16,3,26]. When not associated with neurological disorders, RBD is termed idio- pathic (iRBD). The idiopathic form accounts for up to 60% of cases described in the literature [30]. However, follow-up of iRBD patients revealed that subsequent emergence of a synu- cleinopathy is frequent in these patients [29]. Furthermore, sev- eral neurological abnormalities, such as cortical EEG slowing, subtle neuropsychological deficits, mild autonomic dysfunction and decreased striatal dopaminergic innervation, have all been reported in patients with iRBD, suggesting that this condition may represent a pre-clinical stage of a synucleinopathy [13]. Recently, a widespread and stereotyped pattern of patho- logical progression has been described in Lewy body disease, 0361-9230/$ – see front matter © 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.brainresbull.2006.07.008