Flickering Stimuli Do Not Reliably Induce Visual Hallucinations in Parkinson's Disease.

Angeliki Zarkali,Andrew J Lees,Rimona S Weil

doi:10.3233/jpd-191635

Angeliki Zarkali, Andrew J Lees + Show 1 more

Open Access

https://doi.org/10.3233/jpd-191635

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Abstract

Visual hallucinations are a common and often distressing feature of Parkinson’s disease; they are ephemeral and capricious, making them difficult to study but tend to be more prominent in dim illumination. Flickering stimuli can induce simple hallucinations even in healthy individuals. We tested a stroboscope and an equivalent full-screen flickering stimulus in 16 participants: 7 patients with Parkinson’s and habitual visual hallucinations, 6 Parkinson’s patients without hallucinations and 3 controls. Both flicker sources induced varied geometrical hallucinations in 4 participants (25%) and complex hallucinations in 1 but neither induced typical Parkinson’s-associated hallucinations.

Highlights

Visual hallucinations are a frequent and often distressing symptom of Parkinson’s disease (PD) affecting 30–70% of patients [1, 2]
We reasoned that flicker might be a useful “stress-test”, that could be used in routine clinical settings to determine whether a patient with PD was at risk of visual hallucinations or as a tool to induce hallucinations in experimental conditions
Participants viewed the stroboscope at a 30 cm distance; they faced the lightbulb with their eyelids shut

Summary

Introduction

Visual hallucinations are a frequent and often distressing symptom of Parkinson’s disease (PD) affecting 30–70% of patients [1, 2]. The phenomenology of PD-associated hallucinations is rich and varied, including both complex formed visual imagery in the absence of a stimulus (the classical definition of hallucinations [3]), and other hallucinatory phenomena such as less formed passage hallucinations, misperceptions and illusions [1, 2,3,4]. When phantasmagorical they can sometimes be distressing and frightening and have been associated with increased mortality [5], higher likelihood of nursing home placement [6], worse quality of life [7] and increased carer burden [6]. We reasoned that flicker might be a useful “stress-test”, that could be used in routine clinical settings to determine whether a patient with PD was at risk of visual hallucinations or as a tool to induce hallucinations in experimental conditions

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