The chief complaint in the ER chart was listed as Hallucinations.
“We are not here for the hallucinations,” my patient stated at the outset of our interaction.
It was true that she was seeing frequent visual hallucinations. She could describe them vividly as tiny Mary Poppins figures seen hovering over her bed with raised umbrellas. When she looked outside she saw tiny soldiers crouched in the bushes or marching in formation down the street. She was not bothered by these hallucinations and knew that they were not real, although she could see them clearly.
“That is just her Charles Bonnet syndrome,” her husband assured me. She confidently agreed with him.
“Been going on for years, ever since my glaucoma got bad,” she added. “I am used to them now.”
Charles Bonnet syndrome (CBS) is a somewhat common phenomenon in people who have severe vision loss. Charles Bonnet first described it in 1760 after observing it in his 87-year-old grandfather. Bonnet was a lawyer, not a physician, but he was also a self-taught biologist.
My patient had advanced macular degeneration, which affects central vision, combined with glaucoma, which affects peripheral vision. With her visual input so diminished her brain began forming its own images not based on any objective reality.
The visions in CBS—classified as visual release hallucinations–are usually lilliputian figures, very small, and often described as cartoons by the patients. Many patients see striking geometric formations.
Visual release hallucinations occur when the visual pathways in the brain circuits are starved for input. Lacking any incoming neural impulses from the retina and optic nerves, the brain begins to misinterpret the background electrical “noise” that the neurons themselves make as part of their normal metabolism as visual input.
Visual release hallucinations can be seen in people kept in complete darkness for long periods of time. They manifest as weird lights and figures when there is no light. They have been dubbed the “prisoner’s cinema.” The more scientific term for these are phosphenes—the experience of seeing light without light actually entering the eye. You can create your own phosphene very easily. Just close your eyes and firmly push on the right side of your right eye. You will see a small semi-circle of bright white light in the left side of that eye.
Sir Isaac Newton was the first to describe this effect, which results from the pressure stimulation on the retinal light detection cells causing tiny electrical electric pulses to transmit to the brain and be interpreted as light. And that is how Charles Bonnet syndrome occurs. Misinterpreted neuronal inputs. We are all susceptible.
So if she was not here for the hallucinations though, what was she here for?
Her husband explained that she had been in a serious car crash (yes, she was driving up until recently) in South Carolina. She was hospitalized for several days for a head injury. While in the hospital she developed a fixed delusion that the hospital was in fact inside her home in Charlottesville. When the hospital could offer the couple no explanation for this weird delusion her husband decided to check her out and have her seen at our hospital.
When I talked with her about this it became apparent that she thought our hospital had somehow been built inside her house as well. In addition, during the trip to Charlottesville they had stayed in a hotel that she also thought was part of her home, and a restaurant as well. She knew on some level that it sounded absurd, but it felt so real to her that she could not help but believe it despite its illogic. Like the prisoners in Plato’s Cave analogy, she was receiving distorted information through her sensory pathways and interpreting it to draw skewed conclusions. But she had to make sense of it somehow; this is the human condition.
Her delusion is called reduplicative paramnesia, a type of delusional misidentification disorder like Capgras syndrome, previously discussed in this column. By a historical coincidence, this paramnesia was also first described by Charles Bonnet, in 1789, although he did not recognize it as a syndrome as he only saw one case.
Reviewing the head CT done in South Carolina, it was clear that she had suffered damage to the right side of her brain and this likely accounted for her delusion, as this has been well described in this type of injury. Only time will tell if her condition is permanent. I suspect it will be. But as delusions go, this one was pretty comforting. She was always at home, no matter where she went.