Impaired sense of smell and color discrimination in monogenic and idiopathic Parkinson's disease

• Published in: Movement disorders Vol. 25; no. 15; pp. 2665 - 2669
• Main Authors: Kertelge, Lena, Brüggemann, Norbert, Schmidt, Alexander, Tadic, Vera, Wisse, Claudia, Dankert, Sylwia, Drude, Laura, van der Vegt, Joyce, Siebner, Hartwig, Pawlack, Heike, Pramstaller, Peter P., Behrens, Maria Isabel, Ramirez, Alfredo, Reichel, Dirk, Buhmann, Carsten, Hagenah, Johann, Klein, Christine, Lohmann, Katja, Kasten, Meike
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 15.11.2010; Wiley; Wiley Subscription Services, Inc
• Subjects: Aged; alpha-Synuclein - genetics; Biological and medical sciences; color discrimination; Color Perception - genetics; Color Vision Defects - genetics; Color Vision Defects - physiopathology; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Discrimination (Psychology) - physiology; Female; Genetic Testing; Humans; Male; Medical sciences; Middle Aged; monogenic parkinsonism; Movement disorders; Mutation; Neurology; Olfaction Disorders - genetics; Olfaction Disorders - physiopathology; Parkinson Disease - genetics; Parkinson Disease - physiopathology; Parkinson's disease; sense of smell; Smell - genetics; Statistics, Nonparametric; Nervous system diseases; Parkinson's disease; monogenic parkinsonism; Color; Idiopathic; Parkinson disease; color discrimination; Cerebral disorder; Parkinsonism; Discrimination; Central nervous system disease; sense of smell; Degenerative disease; Extrapyramidal syndrome
• ISSN: 0885-3185; 1531-8257; 1531-8257
• DOI: 10.1002/mds.23272

Olfaction is typically impaired in idiopathic Parkinson's disease (IPD), but its role is uncertain in monogenic PD. Diminished color discrimination has been suggested as another early sign of dopaminergic dysfunction but not been systematically studied. Furthermore, it is unknown whether both deficits are linked. We examined 100 patients with IPD, 27 manifesting mutation carriers (MC), 20 nonmanifesting mutation carriers (NMC), and 110 controls. Participants underwent a standardized neurological examination, the University of Pennsylvania Smell Identification Test (UPSIT), the Farnsworth‐Munsell (FM) color discrimination test, and mutation testing in known PD genes. The monogenic group consisted of 15 Parkin (6MC/9NMC), 17 PINK1 (10MC/7NMC), 8 LRRK2 (4MC/4NMC), 3 SNCA (MC), and 4 ATP13A2 (MC) carriers. Olfaction was most impaired in IPD (UPSIT percentiles 10.1 ± 13.5) compared with all other groups (MC 13.8 ± 11.9, NMC 19.6 ± 13.0, controls 33.8 ± 22.4). Within MC, carriers of two mutations in Parkin and PINK1 showed higher UPSIT percentiles than LRRK2 and SNCA carriers. Color discrimination was reduced in IPD (FM total error score 134.8 ± 92.7). In MC (122.4 ± 142.4), the reduction was most pronounced in LRRK2, NMC (80.0 ± 38.8) were comparable with controls (97.2 ± 61.1). UPSIT and FM scores were correlated in the control (r = −0.305; P = 0.002) and the IPD group (r = −0.303; P = 0.006) but not among mutation carriers. First, we confirmed olfaction and color discrimination to be impaired in IPD and suggest olfaction to be a premotor sign. Second, olfaction differed between carriers with one and two mutations in Parkin/PINK1‐associated PD. Third, olfaction and color discrimination impairment do not necessarily evolve in parallel. © 2010 Movement Disorder Society