To diagnose dementia, DSM-IV requires the presence of multiple cognitive deficits manifested by memory impairment and one or more of the following:
- aphasia
- apraxia
- agnosia
- disturbance of executive functioning.2
Ms. K exhibited none of these characteristics, and she retained full executive function—she could balance her checkbook, buy groceries, and cook for herself. Also, her MMSE score was high.
Ms. K showed no consciousness fluctuations or attention deficits, two features commonly seen in delirium. She was alert and oriented throughout the interview, and her flow of thought, speech, language, and attention were appropriate. Therefore, delirium can be reasonably excluded.
The hallucinations probably do not signal onset of schizophrenia because of Ms. K’s age at presentation, lack of family history of psychotic disorder, and paucity of negative symptoms. Auditory hallucinations are much more common in psychosis, and isolated visual hallucinations rarely occur in schizophrenia.
Finally, Ms. K’s electrophysiologic, laboratory, and imaging studies revealed isolated systolic hypertension, low visual acuity, and a mild gait disturbance. Severe left lens opacification accounted for the patient’s discordant pupillary light reflex. None of these findings explained her visual hallucinations, however.
Is a non-psychiatric disorder causing Ms. K’s hallucinations? What type of medication might alleviate her symptoms?
The authors’ observations
Given Ms. K’s strong cognitive function and poor visual acuity, we concluded that her hallucinations may fit the criteria for Charles Bonnet syndrome (CBS), a poorly understood medical phenomenon.
CBS is characterized by complex visual hallucinations in visually impaired elderly patients without cognitive deficits (Table 2).3,4 Swiss philosopher Charles Bonnet first described the disorder in 1760 to explain the vivid visual hallucinations of his 89-year-old grandfather, who had severe cataracts but no cognitive deficits.3 Bonnet’s grandfather claimed to have visions of men, women, birds, buildings, and tapestries.3
CBS is increasingly recognized and reported, but the medical community has never formed a universally accepted definition for this phenomenon. Persons with CBS react positively or negatively to their hallucinations, and the images may stimulate anxiety, anger, or mild paranoia. Research has focused on prevalence, risk indicators, and treatment.
Table 2
Charles Bonnet syndrome: fast facts
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Teunisse et al determined that visual hallucinations plague up to 14% of sight-impaired persons.4,5 The hallucinations vary widely: people, animals, flowers, vehicles, buildings, and sometimes complete scenes.4,5 Significant risk factors for CBS include advanced age and low visual acuity.4,5 Loneliness, introversion, and shyness are additional risk indicators in older, visually handicapped persons.6 Therefore, social isolation may be a predisposing factor.
Drug treatment of visual hallucinations in CBS currently includes antipsychotics, such as quetiapine (25 to 100 mg/d) and risperidone (0.25 to 1.0 mg/d).7 However, mixed results have been reported after use of antipsychotics in CBS; one patient’s visual hallucinations were exacerbated after risperidone was initiated.8 Case reports have also described the use of valproate, carbamazepine, and ondansetron in CBS.9-11
Empathy and patient education are the cornerstones of CBS treatment.3 Patients need to be reassured that their visions are benign. For many, simply increasing the amount of ambient light in the home can reduce hallucinations.
TREATMENT A frog in the toilet
Ms. K was started on quetiapine, 25 mg bid, to try to promote restorative sleep and resolve her hallucinations. Up to 18% of persons treated with quetiapine report somnolence as an adverse effect, vs. 3 to 8% of those treated with risperidone.12
During her hospital stay, Ms. K experienced no visual hallucinations during the day but reported seeing a grayish-brown bullfrog in the toilet at night. This hallucination did not frighten her; she would simply close the bathroom door and wait until the bullfrog “disappeared.”
Her sleep improved, as did her appetite. She participated in daily group sessions and socialized with other patients.
After 12 days, Ms. K was discharged. To decrease her social isolation, we encouraged her to participate in a day program for seniors. We also continued her on quetiapine, 25 mg bid.
Five months later, her primary care physician reports that Ms. K remains symptom free while maintaining her quetiapine dosage.
Related resources
- Royal National Institute of the Blind: Fact sheet for Charles Bonnet syndrome. Available at: http://www.rnib.org.uk/info/cbsfin.htm
- Verstraten PFJ. The Charles Bonnet syndrome: Development of a protocol for clinical practice in a multidisciplinary approach from assessment to intervention. Available at: http://www.rehab-syn.enter.iris.se/kc-syn/cb.htm
- Adamczyk DT. Optometric educators. Am I seeing things? Optometry Today June 18, 1999:37-9. Available at: http://www.optometry.co.uk/articles/19990618/Adamczyk.pdf