Abstract
BackgroundComplex visual hallucinations are common in Lewy body dementia (LBD) and can cause significant patient and caregiver distress. Current treatments are primarily pharmacological in nature and have limited efficacy and associated side effects. The objective of this study was to assess the effects of consecutive sessions of transcranial direct current stimulation (tDCS) on visual hallucination frequency and severity in LBD, at short-term and long-term follow-up stages.MethodsThe study was a randomised, double-blind, placebo-controlled trial involving 40 participants with LBD (Mage = 75.52 years, SDage = 8.69 years) which was conducted at a single site between November 2013 and December 2017. Participants received two consecutive 20-min sessions of active (0.048 mA/cm2) or placebo tDCS, separated by a 30-min break, over 5 consecutive days. The anodal electrode was applied to the right parietal cortex (P4) and the cathodal electrode was applied to the occipital cortex (Oz). The primary outcome measure was the Neuropsychiatric Inventory (NPI) hallucinations subscale, as completed by a caregiver/informant at baseline and day 5 (short-term) follow-up, and month 1 and month 3 (long-term) follow-up. Secondary outcome measures included visual cortical excitability, as measured using transcranial magnetic stimulation, computerised attentional and visuoperceptual tasks, and measures of global cognition and cognitive fluctuations.ResultsComplete study data were obtained from 36 participants. There was an overall improvement in visual hallucinations (NPI) for both groups at day 5 relative to baseline, with a medium-to-large effect size; however, compared to placebo, active tDCS did not result in any improvements in visual hallucinations (NPI) at day 5 relative to baseline, or at month 1 or month 3 follow-up time points. Additionally, comparisons of secondary outcome measures showed that active tDCS did not result in any improvements on any measure (visual cortical excitability, attentional and visuoperceptual tasks or cognitive measures) at any time point.ConclusionsRepeated consecutive sessions of parietal anodal tDCS, and occipital cathodal tDCS, do not improve visual hallucinations or visuoperceptual function, or alter visual cortical excitability in LBD.Trial registrationISRCTN, ISRCTN40214749. Registered on 25 October 2013.
Highlights
Complex visual hallucinations are common in Lewy body dementia (LBD) and can cause significant patient and caregiver distress
The current study aimed to examine whether active transcranial direct current stimulation (tDCS) reduced visual cortical excitability and improved visuoperceptual function, as secondary outcome measures
Participant flow A total of 40 participants (26 dementia with Lewy bodies (DLB), 14 Parkinson’s disease with dementia (PDD); Mage = 75.52 years, SDage = 8.69 years) were entered into the study
Summary
Complex visual hallucinations are common in Lewy body dementia (LBD) and can cause significant patient and caregiver distress. Current treatments are primarily pharmacological in nature and have limited efficacy and associated side effects. DLB is a common cause of degenerative dementia in older people after Alzheimer’s dementia (AD), accounting for up to 7.5% of all diagnosed dementia cases in secondary care [1, 2]; and in Parkinson’s disease (PD), dementia is a common long-term outcome, affecting up to 80% of patients [3]. Treatments for visual hallucinations in DLB and PDD are primarily pharmacological in nature and are typically limited to the use of cholinesterase inhibitors and antipsychotic agents [10]; these agents have been shown to have only limited efficacy and, in the case of antipsychotic medications, are typically associated with significant morbidity and mortality risks. There is an urgent need for alternative methods of treatment
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