Lack of improvement in odor identification by levodopa in humans

UPSIT subitems may predict motor progression in Parkinson's disease

Background

The relationship between hyposmia and motor progression is controversial in Parkinson's disease (PD). The aim of this study was to investigate whether preserved identification of Chinese-validated University of Pennsylvania Smell Identification Test (UPSIT) odors could predict PD motor progression.

Methods

PD patients with two consecutive clinical visits while taking medication were recruited. Based on mean changes in Movement Disorder Society Unified Parkinson's Disease Rating Scale part 3 score and levodopa equivalent daily dosage, the participants were categorized into rapid progression, medium progression, and slow progression groups. Odors associated with the risk of PD motor progression were identified by calculating the odds ratios of UPSIT item identification between the rapid and slow progression groups. Receiver operating characteristic curve analysis of these odors was conducted to determine an optimal threshold for rapid motor progression.

Results

A total of 117 PD patients were screened for group classification. Preserved identification of neutral/pleasant odors including banana, peach, magnolia, and baby powder was significantly correlated with rapid motor progression. The risk of rapid progression increased with more detected risk odors. Detection of ≥1.5 risk odors could differentiate rapid progression from slow progression with a sensitivity of 85.7%, specificity of 45.8%, and area under the receiver operating characteristic curve of 0.687.

Conclusion

Preserved identification of neutral/pleasant odors may help to predict PD motor progression, and detection of ≥1.5 UPSIT motor progression risk odors could improve the predictive power. In PD patients with a similar level of motor disability during initial screening, preserved pleasant/neutral odor identification may imply relatively better cortical odor discriminative function, which may suggest the body-first (caudo-rostral) subtype with faster disease progression.

Using the Chinese Smell Identification Test to explore olfactory function in Parkinson's disease

Introduction: The Chinese Smell Identification Test (CSIT) was developed specifically for Chinese populations. This work investigated the utility of this test in detecting Parkinson's disease (PD). Olfactory dysfunction is a common non-motor symptom of PD. There are different opinions on the efficacy of drugs for anosmia in PD.Objective: To investigate the olfactory function of Chinese PD patients, verify the effectiveness of the CSIT, and further detect the effects of dopaminergic drugs on anosmia.Methods: In total, 149 PD patients were recruited from the First Affiliated Hospital of Anhui Medical University and 149 healthy comparison participants (HCP) were recruited from the Institute of Psychology of the Chinese Academy of Sciences. The CSIT was used for olfactory function testing in all participants.Results: CSIT scores were significantly lower in the PD group than in the HCP group (t(296) = -12.797, P < 0.001, d = 1.48). Receiver operating characteristic curve analysis showed that the optimal threshold value for the olfactory recognition test was 22.5, which had a sensitivity and specificity of 71.1% and 89.3%, respectively, for the detection of Parkinson's disease. Sex showed a significant influence on CSIT score (t = -3.552, P = 0.001), with males being more likely to develop olfactory dysfunction. We found CSIT scores of the non-medication group and the group with medication were lower than those of the HCP group, and the difference was statistically significant (t(82) = -7.116, P < 0.0167, d = 1.59; t(82) = -4.907, P < 0.0167, d = 1.10). CSIT scores of the group with medication were significantly higher than those of the non-medication group (t(41) = -3.067, P < 0.0167, d = 0.41).Conclusions: In China, the CSIT is recommended to improve the sensitivity of PD detection. The olfactory function of PD patients was improved after treatment with dopaminergic drugs.

Unilateral olfactory deficit in a hemiparkinson's disease mouse model

Parkinson's disease is a neurodegenerative disease which often presents hyposmia (80-90% of the cases). We characterized the olfactory behavior in the model of 6-hydroxydopamine of Parkinson's disease. Mice were trained to discriminate between two odorants in a radial maze. One of the odorants was associated with water as a reward. 6-hydroxydopamine was injected directly into the dorsal striatum; after complete striatal denervation, olfactory performance was evaluated in a radial maze. In the first evaluation, experimental mice performed as control mice. After the first evaluation, the narine of the contralateral side to the striatal injection was closed and mice were evaluated again. The experimental group completely lost the capacity to discriminate between the odorant associated with the reward (heptaldehyde) and the unconditioned odorant (2-heptanone). We propose that the olfactory deficit was caused by dopaminergic denervation to the olfactory tubercle and nucleus accumbens.

Suprathreshold odor intensity perception in early-stage Parkinson's disease

BACKGROUND

Whether Parkinson's disease (PD) influences suprathreshold changes in perceived odor intensity is unknown. In patients with Alzheimer's disease, patients with schizophrenia, and the elderly, such perception is reportedly normal. If generally true, this could reflect a core element of the olfactory system insulated to some degree from age- and disease-related pathological conditions.

METHODS

Odor intensity ratings for pentyl acetate were obtained from 29 early-stage PD patients when on and off dopamine-related medications (DRMs) and from 29 matched controls.

RESULTS

The ratings were significantly attenuated at the higher odorant concentrations, with the degree of attenuation associated with overall olfactory dysfunction. Ratings were higher on the right than on the left side of the nose of both patients and controls. No associations with DRMs, Unified Parkinson's Disease Rating Scale (UPDRS) scores, or striatal dopamine transporter imaging were found.

CONCLUSIONS

Parkinson's disease (PD) influences suprathreshold estimates of perceived odor intensity, negating the notion that such perception might be spared in this disease. No association with dopaminergic processes was apparent.

Olfactory training in patients with Parkinson's disease

OBJECTIVE

Decrease of olfactory function in Parkinson's disease (PD) is a well-investigated fact. Studies indicate that pharmacological treatment of PD fails to restore olfactory function in PD patients. The aim of this investigation was whether patients with PD would benefit from "training" with odors in terms of an improvement of their general olfactory function. It has been hypothesized that olfactory training should produce both an improved sensitivity towards the odors used in the training process and an overall increase of olfactory function.

METHODS

We recruited 70 subjects with PD and olfactory loss into this single-center, prospective, controlled non-blinded study. Thirty-five patients were assigned to the olfactory training group and 35 subjects to the control group (no training). Olfactory training was performed over a period of 12 weeks while patients exposed themselves twice daily to four odors (phenyl ethyl alcohol: rose, eucalyptol: eucalyptus, citronellal: lemon, and eugenol: cloves). Olfactory testing was performed before and after training using the "Sniffin' Sticks" (thresholds for phenyl ethyl alcohol, tests for odor discrimination, and odor identification) in addition to threshold tests for the odors used in the training process.

RESULTS

Compared to baseline, trained PD patients experienced a significant increase in their olfactory function, which was observed for the Sniffin' Sticks test score and for thresholds for the odors used in the training process. Olfactory function was unchanged in PD patients who did not perform olfactory training.

CONCLUSION

The present results indicate that olfactory training may increase olfactory sensitivity in PD patients.

The predictors of parent reported behaviors related to olfactory information processing in children with ADHD

OBJECTIVE

Attention deficit hyperactivity disorder (ADHD) is a heterogeneous disorder with contradictory findings about smell detection function. It is not clear if the parent perceived behavior related to olfactory function is associated with age, gender, severity of ADHD, and cooccurring symptoms of anxiety and oppositional behavior in children with ADHD.

METHODS

Participants were a clinical sample of 104 children and adolescents with ADHD using DSM-IV diagnostic criteria by a semi-structured interview. Parent perceived behavior related to olfactory processing function was assessed trough a questionnaire. The parent reported Olfactory Functioning Checklist was used to evaluate "seeking behavior and over-responsiveness to smell (SSBO)" and "smell detection ability (SDA)".

RESULTS

ADHD and separation anxiety symptoms count (severity) predicted the SDA scale score. None of the variables of gender, age, ADHD subtypes, co-morbidity with oppositional defiant disorder (ODD), and symptom count of ODD predicted SSBO and SDA scales' scores.

CONCLUSION

Parent reported behavior related to olfactory detection impairment increased with higher ADHD and anxiety severity. It is independent of age and gender.