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Visual Hallucination: Charles Bonnet Syndrome

Visual Hallucination: Charles Bonnet Syndrome

A pleasant 80-year-old woman who lives independently comes with her daughter to the emergency department complaining of visual hallucinations that have become progressively worse. She does not have a history of dementia or psychosis.

The patient underwent left eye cataract surgery approximately 3 weeks earlier and reports experiencing intermittent visual hallucinations since that time. She described initially seeing family members who were no longer alive. The nature of the hallucinations had become more menacing, however, and she had called the police the evening before this hospital visit. She believed she had seen a man in her house and that he had dropped off a child. She believed the child did not have legs. She was concerned that she was unable to care for the child.

She admitted feeling anxious about the situation but said she she had not seen anyone out of the ordinary since she arrived at the hospital. She denied hearing voices and did not exhibit delusional symptoms.

The patient’s past medical/surgical history was significant for hypertension; open angle glaucoma (unmedicated since surgery); recent cataract surgery; clipping for cerebral aneurysm; and dilation for esophageal stricture.

She denied any tobacco, alcohol, or drug abuse. She had no known drug allergies and family history was non-contributory. Her current medications were losartan potassium 50 mg, twice daily; nebivolol 10 mg, twice daily; alprazolam 0.25 mg 3 times daily, as needed for anxiety; and brimonidine eye drops 1 drop and brinzolamide eye drops 1 drop, each 3 times daily. Review of systems was otherwise negative.

On physical examination, she appeared well and in no acute distress. Vital signs were stable. Systemic examination, including neurologic and fundoscopic examination, revealed no gross abnormalities. A mental status examination did not reveal mood or cognitive deficit. She denied any history of underlying mental illness and denied any auditory hallucinations.

Laboratory studies found complete blood cell count and comprehensive metabolic panel within normal limits. No evidence of drug or alcohol use was found. Thyroid-stimulating hormone and vitamin B12 levels also were within normal range. ECG reading was normal. CT of the brain showed postoperative changes from previous fronto-temporal craniotomy for aneurysm clipping. Chronic encephalomalacia was observed in the left frontal and temporal lobes. There was no acute intracranial hemorrhage or cortical infarction seen. Moderate atrophy was observed. 

On the basis of the clinical history and examination, a diagnosis of Charles Bonnet syndrome was made. The patient was admitted and examined by Neurology and Ophthalmology. Findings on examinations and evaluations were negative. She denied visual hallucinations during the observation period and resumed her home medications. She was discharged in good condition and directed to follow up with her primary care physician.

Charles Bonnet syndrome (CBS) is an uncommon condition that causes visual hallucination in patients who do not have mental illness. The majority of patients with CBS are elderly, with a mean age of 70 to 85 years.3 Most have some degree of visual impairment or deafferentation of the visual cortex.1-3

Charles Bonnet, a Swiss philosopher, first described the syndrome in 1760 in a publication describing visual hallucination experienced by his grandfather who was blind secondary to cataract but otherwise physically and mentally healthy. It was not until 1937, however, that a Swiss scientist, George de Morsier, labeled the condition as Charles Bonnet syndrome.1

The diagnostic criteria for CBS remain controversial. The most widely accepted are (1) the presence of formed, complex, persistent or repetitive, stereotyped visual hallucinations in a partially sighted person; (2) full or partial insight into the unreal nature of the perceptions; (3) absence of hallucinations on other sensory modalities; and (4) absence of mental disorders.2

The number of reported cases is increasing as the population ages and the prevalence of ophthalmologic4 and cerebral diseases increases proportionately, including age-related macular degeneration, cataract, glaucoma, diabetic retinopathy, cerebrovascular disorders, and Alzheimer disease. The estimated prevalence is 0.5% to 17%.5 It is difficult to interpret, however, because of differences in diagnostic criteria for CBS and in the methods used to evaluate the visual hallucinations.6

Visual hallucinations are also under-reported by patients who fear the symptoms represent psychiatric disease or who lack insight into unreal nature of hallucinations.1 Up to 60% of patients with CBS are hesitant to tell their physician about their visual hallucinations for fear of being labeled with mental illness or dementia.8 A large prospective study in the Netherlands found a history of diminished visual acuity or visual field loss as well as elderly age to be the primary factors correlated with CBS.9


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