Andrew G. Lee, MD, Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, TX; Professor of Ophthalmology, Weill Cornell Medicine; Gina Pham, Baylor College of Medicine Class of 2020
Dr. Lee lectures medical students on Charles Bonnet syndrome
We are going to talk about the Charles Bonnet syndrome. Charles Bonnet was a Swiss naturalist, and he described the phenomenon in his grandfather. His grandfather had lost vision, and he had visual hallucinations, which he described as a man in a stove pipe hat. It is often a formed hallucination of a person or animals or something similar. The patients usually have complete insight into the unreal nature of the hallucination. They don't have any auditory component - that is the hallucination doesn't talk, and there can't be any delusional construct behind the visual hallucination. That is there is no reason why the person is there. It's not like the CIA sent them to kill them or anything like that. So it's caused by decreased vision. It can be at any level of visual loss, but most people consider 20/40 kind of the cutoff. It can be unilateral or bilateral vision loss, and most patients just want to be reassured that they're not crazy. So you get to ask them some questions now. #1. Do you know its not real? "Yes." #2. Does it talk to you? "No." #3. Why are they there? "I don't know." So if they answer appropriately and they have this level of vision loss, and they have formed visual hallucinations, we would be thinking of the Charles Bonnet syndrome. You can do an imaging study. but the yield is low. EEG could be done, but it is not likely to be seizure without other symptoms or signs. The treatment, however, is similar to seizure. We use anti-seizure medicines sometimes to help the Charles bonnet. Valproic acid is probably the most commonly used. These usually don't work. Most patients just want reassurance that they are not crazy. So when confronted with a patient who has a visual hallucination that is formed, ask them if it talks to them, do they know its not real, and why it's there. If there is no delusional construct, no auditory component, and they recognize it is unreal, and they have vision loss, you should be thinking about Charles Bonnet syndrome.
Spencer S. Eccles Health Sciences Library, University of Utah