Impaired sense of smell and color discrimination in monogenic and idiopathic Parkinson's disease.
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.
Kertelge
Lena
L
Department of Psychiatry and Psychotherapy, University of Luebeck, Luebeck, Germany.
Brüggemann
Norbert
N
Schmidt
Alexander
A
Tadic
Vera
V
Wisse
Claudia
C
Dankert
Sylwia
S
Drude
Laura
L
van der Vegt
Joyce
J
Siebner
Hartwig
H
Pawlack
Heike
H
Pramstaller
Peter P
PP
Behrens
Maria Isabel
MI
Ramirez
Alfredo
A
Reichel
Dirk
D
Buhmann
Carsten
C
Hagenah
Johann
J
Klein
Christine
C
Lohmann
Katja
K
Kasten
Meike
M
D000368:Aged; D003118:Color Perception / Q000235:genetics; D003117:Color Vision Defects / Q000235:genetics / Q000503:physiopathology*; D004192:Discrimination, Psychological / Q000502:physiology*; D005260:Female; D005820:Genetic Testing; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D000857:Olfaction Disorders / Q000235:genetics / Q000503:physiopathology*; D010300:Parkinson Disease / Q000235:genetics / Q000503:physiopathology*; D012903:Smell / Q000235:genetics*; D018709:Statistics, Nonparametric; D051844:alpha-Synuclein / Q000235:genetics
D051844:alpha-Synuclein