Charles Bonnet Syndrome: Definition and Treatment
What is Charles Bonnet Syndrome?
Charles Bonnet syndrome (CBS) is a condition where patients with vision impairment experience recurrent, vivid visual hallucinations while maintaining full insight that these perceptions are not real, without any other neurological or psychiatric explanation for the hallucinations. 1
The syndrome requires four key diagnostic features to be present: 1
- Recurrent, vivid visual hallucinations (often complex images like faces, geometric patterns, or miniature figures)
- Patient insight that what is seen is not real (distinguishing it from psychotic disorders)
- No other neurological or medical diagnosis explaining the hallucinations
- Some degree of vision loss (from any cause including macular degeneration, glaucoma, cataracts, or visual field defects)
Epidemiology and Pathophysiology
CBS affects 15-60% of patients with ophthalmologic disorders, with more than 20% of people with vision loss experiencing these hallucinations. 1 The wide prevalence range depends on the definition used and population studied. 1
The hallucinations result from a cortical-release phenomenon due to lack of visual input to the brain, representing a form of "phantom vision" from deafferentiation of visual association areas in the cerebral cortex. 1 This is analogous to phantom limb pain after amputation—the brain generates perceptions in the absence of actual sensory input.
How is Charles Bonnet Syndrome Treated?
First-Line Management: Education and Reassurance
The cornerstone of CBS treatment is educating patients and caregivers that phantom vision is common in visually impaired people and reassuring patients that hallucinations do not indicate mental illness. 1 Many patients require only this reassurance about the benign nature of their condition. 2
Self-Management Techniques
Recommend these specific behavioral strategies that may reduce hallucination frequency: 1
- Eye movements (rapid blinking or looking side to side)
- Changing lighting conditions (turning lights on/off or adjusting brightness)
- Distraction techniques (engaging in conversation, listening to music, or tactile activities)
Psychological Support
Consider psychological therapies and support groups for patients with vision loss, particularly for those experiencing distress from their hallucinations. 1
Pharmacological Treatment
For patients requiring medication, selective serotonin reuptake inhibitors (SSRIs), specifically escitalopram, represent the most effective pharmacological option. 3
A case series of 8 patients with CBS who failed antipsychotic treatment showed that escitalopram (mean dose 11.8 mg daily) significantly reduced symptom severity from a Clinical Global Impression score of 5.7 to 1.8 after 8 weeks (p<0.001), with no side effects or adverse events. 3 Another case report demonstrated complete resolution of daily hallucinations within 4 days of starting venlafaxine (an SSRI/SNRI). 4
Antipsychotic medications are often prescribed but have sketchy evidence for efficacy in CBS and should generally be avoided unless atypical features suggest an alternative diagnosis. 3
For CBS patients with comorbid Alzheimer's-type dementia who are losing insight into their hallucinations, donepezil can be considered as it may improve both cognitive function and hallucinations. 2
Novel Therapies
Transcranial direct-current stimulation (tDCS) has shown promise in reducing hallucination frequency in small trials, though this remains investigational. 1
Critical Red Flags Requiring Alternative Diagnosis
These atypical features should raise immediate suspicion of diagnoses other than CBS: 1, 5
- Lack of insight into the unreal nature of images (suggests psychosis)
- Hallucinations that interact with the patient (responding to or commanding the patient)
- Associated neurological signs or symptoms (altered mental status, focal deficits)
- Evolution to include psychotic symptoms (delusions, paranoia, disorganized behavior)
When these features are present, perform comprehensive neurological and psychiatric evaluation with brain MRI to exclude intracranial processes, and consider alternative diagnoses including Parkinson's disease, dementia with Lewy bodies, epilepsy, schizophrenia, or medication side effects. 5 Recent evidence suggests CBS can rarely evolve to include severe psychiatric manifestations, particularly with total vision loss. 6
Diagnostic Workup for Atypical Cases
If red flags are present, obtain: 5
- Brain MRI (preferred over CT for structural abnormalities)
- Complete blood count, comprehensive metabolic panel, toxicology screen, urinalysis
- Medication review (especially anticholinergics, steroids, dopaminergic agents)
- Consider EEG, lumbar puncture, or formal ophthalmological examination based on clinical suspicion
Prognosis
Total visual loss is extremely rare in conditions like age-related macular degeneration that commonly cause CBS. 1 Most patients maintain stable vision with appropriate ophthalmologic management of their underlying eye disease.