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Lookup NU author(s): Dr Kat Da Silva MorganORCiD,
Professor John-Paul TaylorORCiD
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Introduction: Charles Bonnet Syndrome (CBS) occurs in patients who experience recurrent visual hallucinations (VH) secondary to visual impairment in the absence of psychiatric illness or cognitive impairment. Approximately one-third of patients experiencing CBS report significant distress and disruption to their daily lives as a result of VH. However, there are currently no effective treatments for this symptom. Current research suggests that loss of sensory information from the eyes results in increases in spontaneous hyperexcitability in the visual cortex, which contributes to the occurrence of VH. Non-invasive brain stimulation, including transcranial direct current stimulation (tDCS), can be used to modulate cortical activity (either increasing or decreasing excitability) by applying a weak electrical current to the scalp. However, this technique has yet to be tested in CBS and the optimal stimulation parameters needed to produce a therapeutic benefit are unknown.Objectives: This study aimed to investigate the optimal stimulation parameters of inhibitory tDCS required to produce a potentially beneficial therapeutic effect on visual hallucinations in CBS.Patients & methods: Six patients (3 male) diagnosed with CBS experiencing continuous VH throughout their waking hours were recruited and attended King”s College London to receive cathodal stimulation of the occipital cortex. Patients received multiple consecutive stimulations across nine possible occipital cathodal electrode locations at varying intensities (in conjunction with bilateral anodal stimulation of the left and right dorsolateral prefrontal cortex) and were asked to qualitatively report real-time changes to subjective aspects of their VH during and after each stimulation. Occipital resting state EEG was performed before and after stimulation.Results: All patients tolerated stimulation well, including higher current densities (0.32 mA/cm2). Four of six patients reported positive changes to their VH following 1mA inhibitory stimulation of the primary visual cortex, including a decrease to the size, movement, and intensity of VH. Additionally, the same four patients also reported improved access to their remaining vision following stimulation. Post-stimulation EEG analysis observed an increase in the ratio of open:closed eye occipital alpha when compared to pre-stimulation, providing proof of concept evidence that occipital tDCS can modulate key electrocortical rhythms associated with biological changes in visual function and hallucinatory experience.Conclusion: While this study provides tentative evidence for a beneficial therapeutic effect of tDCS in CBS, further placebo-controlled trials are needed.
Author(s): da Silva Morgan K, Taylor J-P, ffytche DH
Publication type: Conference Proceedings (inc. Abstract)
Publication status: Published
Conference Name: 7th International Conference on Non-Invasive Brain Stimulation (NIBS)
Year of Conference: 2020
Print publication date: 01/04/2020
Online publication date: 16/03/2020
Acceptance date: 02/03/2020
Publisher: Elsevier Ireland Ltd.
Series Title: Clinical Neurophysiology