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Olfactory dysfunction in patients with narcolepsy with and without REM sleep behaviour disorder
K Stiasny-Kolster1, S-C Clever, J C Möller
1Department of Neurology, Center of Nervous Diseases, Philipps-University of Marburg, Schwalmstadt-Treysa, Germany. stiasny@med.uni-marburg.de
Brain : a Journal of Neurology
|January 20, 2007
Summary
Olfactory dysfunction, or hyposmia, is common in idiopathic rapid eye movement sleep behaviour disorder (RBD). This study finds narcolepsy itself, not just RBD, is linked to hyposmia, suggesting it
Area of Science:
- Neurology
- Sleep Medicine
- Olfactory Neuroscience
Background:
- Idiopathic rapid eye movement sleep behaviour disorder (RBD) is linked to Parkinson's disease, often preceded by hyposmia.
- Olfactory dysfunction is observed in both idiopathic RBD and narcolepsy with RBD.
- The association between hyposmia and RBD in narcolepsy requires investigation to differentiate RBD-specific effects from narcolepsy-related olfactory changes.
Purpose of the Study:
- To determine if hyposmia in narcolepsy patients with RBD is specific to RBD or if narcolepsy itself is associated with olfactory dysfunction.
- To investigate the prevalence and characteristics of olfactory dysfunction in narcolepsy patients with and without RBD compared to healthy controls.
Main Methods:
- Olfactory function was assessed in 20 narcolepsy patients with RBD, 20 narcolepsy patients without RBD, and 40 age- and gender-matched healthy controls.
- The standardized 'Sniffin' Sticks' test was used to evaluate olfactory threshold, discrimination, and identification.
- Patients were screened for symptoms or signs of early parkinsonism.
Main Results:
- Both narcolepsy groups (with and without RBD) exhibited significantly higher olfactory thresholds, lower discrimination scores, and lower identification scores compared to healthy controls.
- No participants showed symptoms or signs of early parkinsonism.
- Hyposmia was present in narcolepsy patients regardless of the presence or absence of RBD.
Conclusions:
- Narcolepsy itself is associated with olfactory dysfunction, independent of rapid eye movement sleep behaviour disorder.
- Unlike idiopathic RBD, hyposmia in narcolepsy patients with RBD is unlikely to be a preclinical predictor of developing parkinsonism.
- These findings differentiate the underlying causes of olfactory dysfunction in narcolepsy and idiopathic RBD.
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