Three-year prospective study on olfaction of patients with Parkinson's disease.

OBJECTIVE: We conducted a 3-year prospective study on olfaction of patients with Parkinson's disease (PD) in order to examine the severity and frequency of smell disorder in PD using odor identification test, Open Essence (OE) and to verify the validity of olfactory tests as a predictor of cognitive symptom onset of PD. PATIENTS AND METHODS: We conducted a prospective study by performing an annual examination over a 3-year period. For 56 cases diagnosed with PD by the Department of Neurology at our hospital, OE and Jet Stream Olfactometry (JSO) were performed to assess the olfactory function, and Mini-Mental-State Examination (MMSE) was conducted to measure cognitive impairment. RESULTS: At the beginning, 56 cases were examined, of which 42 remained to be followed up for 3 years. Based on the results of baseline, we found a correlation between OE and the average cognitive thresholds of JSO, but did not find any correlation between OE and MMSE. OE (median 4.0→4.0) and the average cognitive thresholds of JSO (median 2.2→1.6)　decreased after 3 years, and MMSE (median 29→29) also declined, but not significantly. At the 3rd year, 6 cases with MMSE score of 23 or less were identified as suspected dementia and 36 cases with more than 24 points were defined as an invariant group. In order to distinguish these two groups, OE scores of baselines were evaluated with a combination of 12 odors. Sensitivity 1.0 and specificity 0.722 were obtained and the sensitivity+specificity value (1.722) was the highest when the number of correct answers was 4 or less using an odor combination of lumber, menthol, Japanese orange, gas for household use, Hinoki cypress and condensed milk. CONCLUSION: When the number of correct answers of 6 odors (lumber, menthol, Japanese orange, gas for household use, Hinoki cypress and condensed milk) is 4 or less in patients with PD, there is a possibility that MMSE declines in 3 years.

Characteristics of Smell Identification Test in Patients With Parkinson Disease.

OBJECTIVES: Parkinson disease (PD) is frequently associated with olfactory disorder at early stage, which is caused by deposition of Lewy bodies emerging from the olfactory bulb to higher olfactory centers. Early detection of olfactory disorder in the patients with PD may lead to the early diagnosis and treatment for this refractory disease. METHODS: Visual analog scale (VAS), Jet Stream Olfactometry, and Japanese smell identification test, Open Essence (OE), were carried out on 39 patients with PD. Thirty-one patients with postviral olfactory disorder (PVOD), which was caused by the olfactory mucosal dysfunction, were also enrolled in this study as control. RESULTS: There were no significant differences in detection thresholds (2.2 vs. 1.4, P=0.13), recognition thresholds (3.9 vs. 3.5, P=0.39) and OE (4.8 vs. 4.2, P=0.47) between PVOD and PD, while VAS scores of PVOD and PD were significantly different (2.0 and 6.2, P<0.01). In OE, significant differences were observed in the accuracy rates of menthol (68% vs. 44%, P=0.04) and Indian ink (42% vs. 15%, P=0.01) between PVOD and PD. Of particular interest, patients with PVOD tended to select "no detectable," while patients with PD tended to select wrong alternative other than "no smell detected." CONCLUSION: Discrepancy between VAS and OE, and high selected rates of wrong alternative other than "undetectable" in OE might be significant signs of olfactory dysfunction associated with PD.