Objective: The aim of this study was to assess olfactory function using Sniffing Sticks Test in groups of patients with Parkinson’s disease, and atypical extrapyramidal essential tremor, and to investigate the possibility of applying this tool as a method of differential diagnosis between these distinct nosologies.

Background: Extrapyramidal disorders are a rapidly growing group of neurologic diseases with high socioeconomic burden and significant impact on quality of life. The most widespread movement disorder in the world is Parkinson’s disease. Its prevalence in the population is sometimes increased by a misdiagnosed movement disorders presenting with similar symptoms (e.g. Essential tremor). This raises the problem of finding an objective diagnostic method to differentiate Parkinson’s disease in clinical practice.

Methods: The olfactory performance was tested in two groups of patients using Sniffing Sticks Test. The first group consisted of 12 patients with tremor-dominant Parkinson’s disease; the second group included 12 patients diagnosed with atypical extrapyramidal form of Essential tremor. Performance was calculated as a summary of points earned for all of three subtests. The result of 30 and higher was considered normosmia, 30-15 points–hyposmia, result less than 15 points indicated functional anosmia.

Results: All patients with Parkinson’s disease were diagnosed with olfactory dysfunction of varying degree: 11 patients (91,7%) had hyposmia, 1 patient (8,3%) had anosmia. In the Essential tremor group only 3 patients (25,0%) had hyposmia, while 9 patients (75,0%) had normal olfactory function. The most significant differences (p<0,01) between groups were registered in the odor identification subtest (9,1±2,3 points in Parkinson’s disease group and 13,2±1,2 points in Essential tremor group).

Conclusions: Olfactory dysfunction is significantly more common in tremor-dominant Parkinson’s disease than in atypical extrapyramidal form of Essential tremor. Impairment of odor identification ability is the most specific finding in Parkinson’s disease. Our study suggests that olfactory assessment using Sniffing Stix Test can be used in clinical practice to differentiate tremor dominant Parkinson’s disease from atypical Essential tremor.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/olfactory-testing-in-differential-diagnosis-of-atypical-essential-tremor-and-tremor-dominant-parkinsons-disease/