Olfactory dysfunction predicts early transition to a Lewy body disease in idiopathic RBD.

Mahlknecht P, Iranzo A, Högl B, Frauscher B, Müller C, Santamaría J, Tolosa E, Serradell M, Mitterling T, Gschliesser V, Goebel G, Brugger F, Scherfler C, Poewe W, Seppi K; Sleep Innsbruck Barcelona Group. Neurology. 2015 Feb 17;84(7):654-8. Epub 2015 Jan 21.

Collaborators (13)
Frauscher B, Gschliesser V, Högl B, Iranzo A, Mahlknecht P, Mitterling T, Müller C, Poewe W, Santamaría J, Scherfler C, Seppi K, Serradell M, Tolosa E.

OBJECTIVE: The aim of the present study was to determine the predictive value of olfactory dysfunction for the early development of a synuclein-mediated neurodegenerative disease in subjects with idiopathic REM sleep behavior disorder (iRBD) over an observational period of 5 years.
METHODS: Thirty-four patients with polysomnography-confirmed iRBD underwent olfactory testing using the entire Sniffin’ Sticks test assessing odor identification, odor discrimination, and olfactory threshold. Patients with iRBD were prospectively followed up over a period of 4.9 ± 0.3 years (mean ± SD). The diagnosis of neurodegenerative diseases was based on current clinical diagnostic criteria.
RESULTS: After 2.4 ± 1.7 years (mean ± SD), 9 patients (26.5%) with iRBD developed a Lewy body disease (6 Parkinson disease and 3 dementia with Lewy bodies). The entire Sniffin’ Sticks test and the identification subtest had the same overall diagnostic accuracy of 82.4% (95% confidence interval: 66.1%-92.0%) in predicting conversion. The relative risk for a Lewy body disease in the lowest tertile of olfactory function was 7.3 (95% confidence interval: 1.8-29.6) compared with the top 2 tertiles.
CONCLUSIONS: Assessment of olfactory function, particularly odor identification, may help to predict the development of a Lewy body disease in patients with iRBD over a relatively short time period and thus to identify patients suitable for future disease modification trials.

Ventana Científica. Diciembre 2015. Artículo 80
Olfactory dysfunction predicts early transition to a Lewy body disease in idiopathic RBD.