CBS frequently goes unrecognized in clinical practice.9 Patients who admit to experiencing hallucinations often are labeled demented or psychotic.10 The course of CBS is categorized in 3 patterns:
- episodic (in this least common pattern, hallucinations occur over days to months and then resolve)
- periodic (hallucinatory activity alternates with phases of remission)
- continuous (patients experience no hallucination-free intervals).7,11
The pathophysiology of CBS is not fully understood. The deafferentation hypothesis suggests that reduced or absent visual system stimulation leads to increased excitability of areas of the cerebral cortex associated with vision, resulting in phantom vision.6,7,12
CBS has no universally accepted diagnostic criteria; it is a diagnosis of exclusion. Because we ruled out medical and organic causes, dementia, delirium, schizophrenia, and depression with psychotic features—and because Mrs. L had advanced macular degeneration and retinopathy—we believed CBS was a likely diagnosis. We referred her to an ophthalmologist, who confirmed the CBS diagnosis.
TREATMENT: Temporary improvement
We prescribe low-dose lorazepam, 0.5 to 1 mg every 8 hours as needed for agitation, and increase quetiapine to 50 mg up to twice a day as needed. These approaches fail because of excessive sedation and delayed onset of action in relation to the fast onset of Mrs. L’s hallucinations.
Based on a published report, we prescribe gabapentin, 100 mg bid, which seems to help Mrs. L. For several months, her hallucinations are reduced, and she occasionally experiences a hallucination-free day. After several months, however, the frequency of her hallucinations increases. Mrs. L refuses to take a higher dosage of gabapentin because she doesn’t like “a lot of medicine.”
Her cognitive function remains mostly stable over the next few months, with an MMSE score of 23+/-1, which is equal to 25.6 +/- 1 when corrected for unperformed tasks secondary to severe visual impairment. She develops no aphasia, apraxia, or agnosia.
Educating Mrs. L about her illness—reassuring her that she is not “crazy”—helped to decrease her anxiety, as did teaching her family to acknowledge the hallucinations and react appropriately. Mrs. L’s hallucinations are less frequent when she interacts with other people and more frequent when she is alone with less sensory stimulation. Although Mrs. L has not yet recovered, a low dose of gabapentin temporarily decreased hallucinations and anxiety.
The authors’ observations
CBS treatment is based mostly on case reports. No pharmacologic treatment is universally effective, but anticonvulsants may help reduce hallucinations.7 Low-dose gabapentin is reported to have produced permanent remission.13
Patients may benefit from using magnifiers and other low-vision devices to maximize residual sight. Increased social interaction and brighter lighting also may help.7 Reassuring the patient that the hallucinations are not real and do not indicate mental illness can be strongly therapeutic.7 Hallucinations may resolve spontaneously, with improved vision, or with increased social interaction.7
Related Resource
- Menon GJ, Rahman I, Menon SJ, et al. Complex visual hallucinations in the visually impaired: the Charles Bonnet syndrome. Surv Ophthalmol. 2003;48:58-72.
Drug Brand Names
- Donepezil • Aricept
- Gabapentin • Neurontin
- Lorazepam • Ativan
- Quetiapine • Seroquel
Disclosure
The authors report no financial relationship with any company whose products are mentioned in this article or with manufacturers of competing products.