This systematic review of 91 studies (case reports and group designs; >7,300 participants) synthesized evidence on non-visual hallucinations in Parkinson’s disease (PD)—auditory, olfactory, somatic-tactile, gustatory, and “sensed presence.” Reported prevalence varied widely by modality: auditory 1.5% to 72.0%, olfactory 1.6% to 21.0%, somatic-tactile 0.4% to 22.5%, gustatory 1.0% to 15.0%, and sensed presence 0.9% to 73.3%. Multisensory hallucinations were also common (0.4%–80% across studies) and appeared in nearly half of the prevalence reports. Phenomenology was often vivid and elaborate, with experiences that were consuming and distressing.
Evidence for modality-specific predictors (clinical or cognitive correlates) was suggestive but inconsistent, underscoring the need for stronger, replicated studies. Methodological heterogeneity—differences in assessment tools, sampling frames, and case definitions—likely contributed to the broad prevalence ranges. Prospective longitudinal cohorts with standardized phenotyping and concurrent measurement of neuropsychiatric burden and treatment exposure are needed to clarify trajectories and modifiable risk factors. Overall, the high frequency and significant distress burden indicate that non-visual and multisensory hallucinations are clinically meaningful in PD. They warrant greater research focus and routine clinical assessment and management alongside the more widely studied visual hallucinations.
Reference: Toh WL, Yolland C, Gurvich C, Barnes J, Rossell SL. Non-visual hallucinations in Parkinson’s disease: a systematic review. J Neurol. 2023;270(6):2857-2889. doi: 10.1007/s00415-022-11545-6.
Link: https://link.springer.com/article/10.1007/s00415-022-11545-6
