Charles Bonnet Syndrome (CBS)

Charles Bonnet was a naturalist and philosophical writer from the 18^th Century.  In 1760 he described a condition in which vivid, complex visual hallucinations (fictive visual percepts) occur in psychologically normal people.  He documented condition in his then 87-year-old grandfather, who was nearly blind from cataracts in both eyes but perceived men, women, birds, carriages, buildings, tapestries and scaffolding patterns.

Charles Bonnet noted that most people affected are elderly with visual impairments, however the phenomenon does not occur only in the elderly or in those with visual impairments; it can also be caused by damage elsewhere in their optic pathway or brain.

Today, this condition is now known as Charles Bonnet Syndrome and 257-years later there is very little understood about this condition.  Doctors, GP’s and psychologists rarely understand or know of the condition and can regularly misdiagnose the condition.

Up to 60% of patients with Charles Bonnet syndrome are hesitant to tell their doctor about their visual hallucinations for fear of being labelled with a mental illness or dementia.  Misdiagnosis is also common as the syndrome is not recognised by clinicians and is often labelled as psychosis, delirium or early dementia.

Charles Bonnet Syndrome and Dementia

Both patients with the Charles Bonnet syndrome and patients with dementia with Lewy bodies can present with formed visual hallucinations.

Ophthalmologists and retina specialists, in particular, should be familiar with the features of dementia with Lewy bodies because the diagnosis of this condition can allow appropriate intervention and help prevent drug-related side effects.

If there is any suspicion of early dementia in such patients, they may benefit from neuropsychiatric evaluation.

Charles Bonnet Syndrome and Strokes

The effects of a stroke can be wide ranging.  Some symptoms are common such as affected communication and partial paralysis or restriction to part of the body. 

Less well known is that in about 20% of cases of stroke, there can be visual or perceptual consequences.  When a stroke occurs in the visual regions of the brain, there is an increased chance of visual disturbances including CBS.  Unlike most cases of CBS due to eye disease, in many instances of stroke-induced CBS, the affected person retains central vision (visual acuity) even though they may well experience some form of visual field loss.  

The stroke community needs to be aware that CBS is a possible consequence of stroke and that accurate information is available to the stroke-survivor as well as their loved ones.

The Edith Ellen Foundation

As a series of articles this blog aims to bring a better awareness and understanding of what Charles Bonnet Syndrome is and how to receive the correct medical treatment, we will also try to address the why's and how's of misdiagnosis.