Transcranial direct current stimulation in the treatment of visual hallucinations in Charles Bonnet syndrome: A randomized placebo-controlled crossover trial.

da Silva Morgan, Katrina, Schumacher, Julia, Collerton, Daniel, Colloby, Sean J., Elder, Greg, Olsen, Kirsty, Ffytche, Dominic H. and Taylor, John-Paul (2022) Transcranial direct current stimulation in the treatment of visual hallucinations in Charles Bonnet syndrome: A randomized placebo-controlled crossover trial. Ophthalmology, 129 (12). pp. 1368-1379. ISSN 0161-6420

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Abstract

Objective
To investigate the potential therapeutic benefits and tolerability of inhibitory transcranial direct current stimulation (tDCS) on the remediation of visual hallucinations in Charles Bonnet Syndrome (CBS).

Design
Randomized, double-masked(blind), placebo-controlled crossover trial.

Participants
Sixteen individuals diagnosed with CBS secondary to visual impairment caused by eye disease experiencing recurrent visual hallucinations.

Intervention
All participants received four consecutive days of active and placebo cathodal stimulation (current density: 0.29mA/cm2) to the visual cortex (Oz) over two defined treatment weeks, separated by a four-week wash-out period.

Main Outcome Measures
Ratings of visual hallucination frequency and duration following active and placebo stimulation, accounting for treatment order, using a 2x2 repeated measures model. Secondary outcomes included impact ratings of visual hallucinations and electrophysiological measures.

Results
When compared to placebo treatment, active inhibitory stimulation of visual cortex resulted in a significant reduction in the frequency of visual hallucinations measured by the North East Visual Hallucinations Interview, with a moderate-to-large effect size. Impact measures of visual hallucinations improved in both placebo and active conditions suggesting support and education for CBS may have therapeutic benefits. Participants who demonstrated greater occipital excitability on electroencephalography assessment at the start of treatment were more likely to report a positive treatment response. Stimulation was found to be tolerable in all participants with no significant adverse effects reported, including no deterioration in pre-existing visual impairment.

Conclusions
Findings indicate that inhibitory tDCS of visual cortex may reduce the frequency of visual hallucinations in people with CBS, particularly individuals who demonstrate greater occipital excitability prior to stimulation. tDCS may offer a feasible, novel intervention option for CBS with no significant side effects, warranting larger scale clinical trials to further characterize its efficacy.

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