Objective: To describe the prevalence and characteristics of Olfactory Hallucinations (OlfH) in patients with Parkinson’s Disease (PD) in a tertiary movement clinic.

Background: Hallucinations are a non-motor feature of alpha synucleinopathies and occur in 20-50% of patients with PD. Due to a lack of awareness as well as paucity of structured questionnaires/tests that target psychosis assessment with an emphasis on olfactory hallucinations (OlfH), these are often missed during clinical consultations.

Method: Singe site, cross-sectional, IRB approved study. Patients diagnosed with PD per UK brain bank criteria by a movement disorder specialist were consecutively enrolled with informed consent and completed a questionnaire and self-administered a University of Pennsylvania Smell Identification Test (UPSIT). Inability to understand the instructions due to language barrier or severe underlying pathology were exclusion criteria.

Results: 137 of the 147 (93%) patients surveyed completed both the UPSIT and the questionnaire. Of the 137, 37% were female. 25 (18.2%) patients endorsed OlfH, of which 16 (64%) were men. Hallucinations in other sensory modalities were also reported: Visual (16.7%), Auditory (9.48%) and Tactile (7.29%). In the patients with OlfH (n=25); concurrent sensory hallucinations included visual (32%), auditory (24%) and tactile (12%). Concurrent visual hallucinations were more common in the OlfH group (32% compared to 13%,p=0.02). 84% of patients with OlfH had a poor sense of smell objectively (UPSIT showed severe microsmia or anosmia) compared to 70% without OlfH, however this difference was statistically insignificant (p=0.199). The most commonly described hallucinations were “smoke/cigarette smoke”. While most reported that OlfH were infrequent, 18% (n=2) reported hallucinations lasting >1 hour and found them unpleasant and upsetting.

Conclusion: Non-motor symptoms of PD are often missed in routine clinical practice and have far-reaching implications in patient care. OlfH tend to be underreported with prevalence ranging from 2.1% to 10% in prior studies compared to 18.2% in our cohort. These patients also reported a higher frequency of concurrent sensory hallucinations.

References: 1. Papapetropoulos S, Katzen H, Schrag A, et al. A questionnaire-based (UM-PDHQ) study of hallucinations in Parkinson’s disease. BMC Neurology. 2008;8:21. doi:10.1186/1471-2377-8-21. 2. Doty, R. L. (1995). The Smell Identification Test administration manual. Haddon Heights, NJ: Sensonics

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MDS Abstracts - https://www.mdsabstracts.org/abstract/olfactory-hallucinations-as-a-non-motor-sign-of-parkinsons-disease-a-cross-sectional-study/