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Abstract
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.
GLOSSARY
- BDI=
- Beck Depression Inventory;
- CCSIT=
- Cross-Cultural Smell Identification Test;
- DAT=
- dopamine transporter;
- MMSE=
- Mini-Mental State Examination;
- OB=
- olfactory bulb;
- PD=
- Parkinson disease;
- SUV=
- standardized uptake value;
- SVZ=
- subventricular zone;
- UPDRS=
- Unified Parkinson's Disease Rating Scale;
- UPSIT=
- University of Pennsylvania Smell Identification Test;
- VOI=
- volume of interest
Footnotes
Go to Neurology.org for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
Editorial, page 1266
- Received December 4, 2014.
- Accepted in final form April 23, 2015.
- © 2015 American Academy of Neurology
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