Olfactory Loss in Parkinson's Disease

Impairment of olfaction is a characteristic and early feature of Parkinson's disease. Recent data indicate that >95% of patients with Parkinson's disease present with significant olfactory loss. Deficits in the sense of smell may precede clinical motor symptoms by years and can be used to assess the risk for developing Parkinson's disease in otherwise asymptomatic individuals. This paper summarizes the available information about olfactory function in Parkinson's disease, indicating the advantageous use of olfactory probes in early and differential diagnosis

Olfactory fMRI in Patients with Parkinson's Disease

Hyposmia is one of the early signs in idiopathic Parkinson's disease (PD). Olfactory stimuli were applied during fMRI scanning to show disease-related modulation of central nervous system structures and to advance our understanding of olfactory dysfunction in PD patients. All participants received either unpleasant stimuli that smelled like rotten eggs or pleasant ones that smelled like roses. Using a block design at a 1.5 T scanner we investigated a total of 8 PD patients (mean age 60 ± 10.9 years) and 13 age matched controls (mean age 58 ± 9.6 years). PD duration ranged from 1 to 9 years (mean 6.63 years); patients had an average “Unified Parkinson's Disease Rating Scale III” score of 23.25 (range, 6–46). Olfactory function was established using the “Sniffin’ Sticks” test battery. Patients tended to rate the stimuli presented during fMRI scans as less intense, but also as more pleasant than controls. fMRI results revealed differences between PD patients and controls which depended on the type of stimulation. While both pleasant and unpleasant stimulation was associated with lower activation in the amygdalo–hippocampal complex in patients compared to controls, increased activity in response to pleasant stimuli was observed in the striatum and the left inferior frontal gyrus. In contrast, unpleasant stimulation led to hypoactivation of the ventral striatum in patients (but not in controls) and did not enhance left inferior frontal activity. These results may partly reflect differences between PD patients and healthy controls in the processing of primary dimensions of odors, intensity, and valence

Topical Administration of Mometasone Is Not Helpful in Post-COVID-19 Olfactory Dysfunction

Persistent olfactory dysfunction is a major concern post-COVID-19, affecting up to 5% of all patients. Different therapeutic options, including mometasone nasal spray, have been recommended, only some of which have been validated for post-COVID-19 olfactory dysfunction. In this study we psychophysically assessed the effect of intranasally applied mometasone furoate on the recovery of olfaction. The spray was applied with a long applicator so that the olfactory cleft could be reached effectively. After olfactory dysfunction had been confirmed psychophysically using Sniffin’ Sticks, patients were randomly assigned to two different treatment arms: the study group (n = 40) underwent olfactory training and intranasal administration of mometasone furoate twice daily, whereas the control group (n = 46) performed olfactory training only. After a study duration of three months, psychophysical testing of olfaction was repeated using Sniffin’ Sticks. We found no benefit of an additional topical administration of mometasone furoate compared to olfactory training alone. These results psychophysically confirm two previous studies which were based on patients’ subjective self-ratings. Our findings are in contrast to current recommendations for the management of olfactory dysfunction post-COVID-19, which might have to be adapted accordingly

Nonlinear association between chemosensory dysfunction and body mass index

Chemosensory (gustatory and olfactory) dysfunction contributes to obesity, but the association between body mass index (BMI) and chemosensory dysfunction are inconsistently reported. The present study included 4,390 subjects at a Smell and Taste Clinic. Results suggested that both the obesity class II group (BMI ≥ 35) and underweight group (BMI < 18.5) exhibited impaired taste function compared with the normal weight group (p <.05). Comparing with the other groups, the obesity class II group exhibited a higher proportion of impaired bitter identification (8.6%), and the underweight group showed a higher proportion of impaired salty identification (7.9%). When investigating differences for individual tastes, subjects with impaired bitter identification had higher BMI (t = 2.79, p =.005) and lower olfactory scores (p <.05) compared with those with intact bitter identification. Finally, reduced taste scores are associated with an increased BMI (r = −.04, p =.022). This correlation becomes more pronounced with age (F = 1.42, p <.001). Practical Application: The nonlinear association between chemosensory dysfunction and BMI suggested that maintaining the gustatory and olfactory function is of significance for normal metabolism. In obesity regulating bitter taste appears to be more important than the other tastes

High Test-Retest Reliability of the Extended Version of the "Sniffin' Sticks” Test

The "Sniffin' Sticks” test kit is a validated and commonly used tool for assessment of olfactory function in subjects with normal sense of smell and in individuals with smell loss. That test incorporates subtests for odor threshold, discrimination, and identification. To gain higher subtest reproducibility, tests on odor discrimination and odor identification were extended using 32 instead of the usually applied 16 single trials each. In developing the extended Sniffin' Sticks test, a number of preliminary experiments were performed in 46 healthy, normosmic individuals 1) to evaluate intensity and familiarity of the additionally selected odors, 2) to select distractors for the discrimination and identification test, and 3) to evaluate the test-retest reliability of each subtest. Furthermore, the extended test was applied to 126 patients with olfactory loss and 71 normosmic individuals. Follow-up investigation could be performed in 69 controls within an average interval of 4 days. Results revealed significant differences between patients and healthy subjects. Estimated intensity and familiarity of the newly selected 16 items of the discrimination test did not differ significantly from the 16 standard items. Test-retest reliability was found to be r = 0.80 (odor discrimination), r = 0.88 (odor identification), and r = 0.92 (odor threshold). In conclusion, the extended test kit allows a precise evaluation of olfactory function, especially when different olfactory tasks are assessed using individual subtests. Furthermore, the high test-retest reliability of both the 16 and the 32-item tests allows the evaluation of even relatively small changes of olfactory function over time by means of either tes

Long lasting phantosmia treated with venlafaxine

Qualitative olfactory disorders such as parosmia and phantosmia are not well investigated. In particular, the causes and treatment options for phantosmia are largely unknown. We report a case of long lasting phantosmia that disappeared under anti-depressive treatment, raising the question to what extent certain forms of qualitative olfactory disorders are an early symptom of depression

Subtle Differences in Brain Architecture in Patients with Congenital Anosmia

People suffering from congenital anosmia show normal brain architecture although they do not have functional sense of smell. Some studies in this regard point to the changes in secondary olfactory cortex, orbitofrontal cortex (OFC), in terms of gray matter volume increase. However, diffusion tensor imaging has not been explored so far. We included 13 congenital anosmia subjects together with 15 controls and looked into various diffusion parameters like FA. Increased FA in bilateral OFC confirms the earlier studies reporting increased gray matter thickness. However, it is quite difficult to interpret FA in terms of gray matter volume. Increased FA has been seen with recovery after traumatic brain injury. Such changes in OFC point to the plastic nature of the brain.Funding Agencies|Projekt DEAL</p

Subtle Differences in Brain Architecture in Patients with Congenital Anosmia

People suffering from congenital anosmia show normal brain architecture although they do not have functional sense of smell. Some studies in this regard point to the changes in secondary olfactory cortex, orbitofrontal cortex (OFC), in terms of gray matter volume increase. However, diffusion tensor imaging has not been explored so far. We included 13 congenital anosmia subjects together with 15 controls and looked into various diffusion parameters like FA. Increased FA in bilateral OFC confirms the earlier studies reporting increased gray matter thickness. However, it is quite difficult to interpret FA in terms of gray matter volume. Increased FA has been seen with recovery after traumatic brain injury. Such changes in OFC point to the plastic nature of the brain