Stimulation to Visual Cortex Could Reduce CBS Hallucinations in Blind Patients
Non-invasive brain stimulation may be useful in lowering the frequency of visual hallucinations in blind people, according to a recent study. Researchers from Newcastle University and Kings College London have tested a procedure known as "transcranial direct current stimulation" (tDCS) on patients as part of the 18-month study.
It has been discovered that the method, which involves sending a mild electric current between electrodes positioned on a person's head, alters the degree of activity in specific regions of the brain.
What are the findings saying?
Previous studies suggest that the Charles Bonnet Syndrome (CBS) is caused by a loss of information from the eyes, which causes an increase in spontaneous activity in the visual cortex, resulting in the appearance of visual hallucinations. The goal of the study was to decrease this activity and bring it back to normal levels using tDCS.
The study's findings, which were reported in the journal Ophthalmology, suggest that stimulation may lessen the frequency of visual hallucinations in patients with CBS, particularly in those who have higher levels of spontaneous activity in their visual regions of the brain.
“CBS, where people experience visual hallucinations is a common experience for people who develop eye disease and visual loss. We don't unfortunately have any good treatments for CBS and drugs which are typically used are often associated with significant side effects. We are excited by our initial findings that using a form of non-invasive brain stimulation, which was well tolerated and can be delivered in a person's own home, may reduce the frequency of visual hallucinations for people with CBS.“ said Dr. John-Paul Taylor, from Newcastle University's Faculty of Medical Sciences.
The study now needs to shift into a larger, multicenter trial to decide whether this treatment is effective and can be used clinically.
Dr. Dominic ffytche, from the Institute of Psychiatry at King's College London, added, "CBS can be considered a normal response of the brain to loss of vision. Once you know what it is, most people don't need specific treatment. But for those that do, this study provides the first glimpse of what treatment might look like in the future. It is not a cure—CBS did not stop completely for anyone—but by reducing how often hallucinations occur, the hope is we can shift CBS from a highly distressing and unpleasant experience to something that no longer troubles you."
Comparison of occipital power spectral density of treatment responders and nonresponders based on an average of recordings performed prior to both active and placebo stimulation. The shaded areas represent standard errors of the spectral density estimate. Credit: Ophthalmology (2022). DOI: 10.1016/j.ophtha.2022.06.041
CBS hallucinations cause distress in patients
Up to 50% of those with macular degeneration experience CBS hallucinations. Although many people also perceive geometric grids and lattices, they can also be basic, unformed flashes of color, light, or structure.
Others have described having more intricate visual experiences, such as seeing snakes, disembodied heads, and little individuals dressed in ornate clothing. According to about one-third of CBS patients, hallucinations can be upsetting and interfere with everyday activities.
In the study, four consecutive days of active and placebo treatment with non-invasive stimulation to the visual areas of the brain were given to 16 persons with CBS who had recurring visual hallucinations.
