Is normosmic Parkinson disease a unique clinical phenotype?
OBJECTIVE
Olfactory dysfunction is present in the majority of patients with early-stage Parkinson disease (PD) and can precede the onset of motor symptoms by many years. We performed this study to evaluate whether normosmic patients with PD had different clinical features compared to hyposmic patients.


METHODS
We analyzed the data of 208 de novo patients with PD (mean age, 65.4 ± 9.7 years; range, 38-85 years; 104 men) who underwent both olfactory function tests and dopamine transporter (DAT) scans.


RESULTS
Normosmic patients were significantly younger and had fewer motor deficits than hyposmic patients with PD. Striatal subregional DAT activities were comparable between the 2 groups, but intersubregional gradients were significantly higher in normosmic than hyposmic PD. A general linear model showed that normosmic patients with PD showed significantly fewer motor deficits after controlling the patient's age, sex, symptom duration, and DAT activity in the posterior putamen (p = 0.016). Levodopa-equivalent dose at approximately 2.5 years follow-up tended to be lower in normosmic than in hyposmic PD (p = 0.055).


CONCLUSIONS
These results suggest that normosmic PD is a unique clinical phenotype with a more benign course, compared to hyposmic PD. Either less pathologic involvement in the olfactory system or a greater potential for olfactory neurogenesis in normosmic PD may contribute to this benign process compared to hyposmic PD.
From the Department of Neurology (D.H.L., J.H.H., J.J.L., P.H.L., Y.H.S.) and the Severance Biomedical Science Institute (P.H.L.), Yonsei University College of Medicine; and the Department of Nuclear Medicine (J.S.O., I.L., J.S.K.), Asan Medical Center, College of Medicine, University of Ulsan, Seoul, Korea.
Dong H
DH
Lee
From the Department of Neurology (D.H.L., J.H.H., J.J.L., P.H.L., Y.H.S.) and the Severance Biomedical Science Institute (P.H.L.), Yonsei University College of Medicine; and the Department of Nuclear Medicine (J.S.O., I.L., J.S.K.), Asan Medical Center, College of Medicine, University of Ulsan, Seoul, Korea.
Jungsu S
JS
Oh
From the Department of Neurology (D.H.L., J.H.H., J.J.L., P.H.L., Y.H.S.) and the Severance Biomedical Science Institute (P.H.L.), Yonsei University College of Medicine; and the Department of Nuclear Medicine (J.S.O., I.L., J.S.K.), Asan Medical Center, College of Medicine, University of Ulsan, Seoul, Korea.
Jee H
JH
Ham
From the Department of Neurology (D.H.L., J.H.H., J.J.L., P.H.L., Y.H.S.) and the Severance Biomedical Science Institute (P.H.L.), Yonsei University College of Medicine; and the Department of Nuclear Medicine (J.S.O., I.L., J.S.K.), Asan Medical Center, College of Medicine, University of Ulsan, Seoul, Korea.
Jae J
JJ
Lee
From the Department of Neurology (D.H.L., J.H.H., J.J.L., P.H.L., Y.H.S.) and the Severance Biomedical Science Institute (P.H.L.), Yonsei University College of Medicine; and the Department of Nuclear Medicine (J.S.O., I.L., J.S.K.), Asan Medical Center, College of Medicine, University of Ulsan, Seoul, Korea.
Injoo
I
Lee
From the Department of Neurology (D.H.L., J.H.H., J.J.L., P.H.L., Y.H.S.) and the Severance Biomedical Science Institute (P.H.L.), Yonsei University College of Medicine; and the Department of Nuclear Medicine (J.S.O., I.L., J.S.K.), Asan Medical Center, College of Medicine, University of Ulsan, Seoul, Korea.
Phil H
PH
Lee
From the Department of Neurology (D.H.L., J.H.H., J.J.L., P.H.L., Y.H.S.) and the Severance Biomedical Science Institute (P.H.L.), Yonsei University College of Medicine; and the Department of Nuclear Medicine (J.S.O., I.L., J.S.K.), Asan Medical Center, College of Medicine, University of Ulsan, Seoul, Korea. yhsohn62@yuhs.ac jaeskim@amc.seoul.kr.
Jae S
JS
Kim
From the Department of Neurology (D.H.L., J.H.H., J.J.L., P.H.L., Y.H.S.) and the Severance Biomedical Science Institute (P.H.L.), Yonsei University College of Medicine; and the Department of Nuclear Medicine (J.S.O., I.L., J.S.K.), Asan Medical Center, College of Medicine, University of Ulsan, Seoul, Korea. yhsohn62@yuhs.ac jaeskim@amc.seoul.kr.
Young H
YH
Sohn
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003342:Corpus Striatum / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D050483:Dopamine Plasma Membrane Transport Proteins / Q000378:metabolism; D005260:Female; D006801:Humans; D007980:Levodopa / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D055495:Neurogenesis / Q000187:drug effects / Q000502:physiology*; D010300:Parkinson Disease / Q000175:diagnosis / Q000188:drug therapy* / Q000473:pathology; D010641:Phenotype; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods
D050483:Dopamine Plasma Membrane Transport Proteins; D007980:Levodopa