When hallucinations are not psychiatric: a case of visual- auditory charles bonnet syndrome

Introduction

Charles Bonnet Syndrome (CBS) is characterized by visual hallucinations arising from progressive or acute damage along the visual pathway due to conditions such as glaucoma, diabetic retinopathy, and macular degeneration that result in partial or complete vision loss. It is estimated to occur in approximately 11–34% of individuals with visual impairment. Although its exact etiology remains unclear, CBS is not considered a psychiatric disorder [1]. While more common in older adults due to increased prevalence of ocular diseases, it may also occur in younger individuals. Hallucinations are typically well-defined, detailed visual images, and patients have little or no control over them. Spontaneous improvement may occur in about one-quarter of patients. Pharmacological treatments, including antipsychotics and anticonvulsants, have been investigated; however, consistent outcomes have not been demonstrated. CBS is frequently underrecognized and may be misdiagnosed as early dementia or psychosis. Parkinson’s disease, Lewy body dementia, psychosis, occipital epilepsy, and migraine with aura should be considered in the differential diagnosis. Cases with accompanying auditory hallucinations have also been reported. Preservation of insight is a key feature distinguishing CBS from psychotic disorders. Diagnosis is clinical and based on the presence of visual and/or auditory hallucinations in individuals with sensory impairment without psychiatric or cognitive disorders [2,3]. Clinical Case: A 70-year-old woman with no psychiatric history presented with visual hallucinations, including seeing unfamiliar people, snakes emerging from the television, and insects attacking her face. Her vision had markedly deteriorated following cataract surgery one year prior, with visual acuity of 5% in the right eye and 10% in the left eye. Approximately one month after surgery, she began experiencing visual hallucinations of moving animals, which later progressed to include unfamiliar human figures. She retained insight, recognizing that the images were not real, and reported that they disappeared upon approaching them. Over the past six months, auditory hallucinations developed, including religious chants and occasional screams. The patient had a 20-year history of progressive bilateral sensorineural hearing loss due to Meniere’s disease and used hearing aids. Despite treatment with olanzapine 5 mg/day initiated six months earlier, her symptoms persisted. She reported no significant cognitive impairment apart from mild memory complaints (Mini-Mental State Examination score: 27). Her medical history included essential hypertension. Cranial MRI and electroencephalography findings were unremarkable, and neurological examination revealed no abnormalities other than visual and hearing impairment. The patient was diagnosed with visual-auditory CBS. Olanzapine was discontinued, and clonazepam 2 mg/day and carbamazepine 200 mg/day were initiated. At one-month follow-up, auditory hallucinations had resolved in the right ear and decreased in the left, while visual hallucinations had also diminished. Conclusion: This case highlights that visual and auditory hallucinations in individuals with sensory impairment do not necessarily indicate psychiatric illness. Preserved insight, normal cognition, and unremarkable neurological findings support the diagnosis of CBS. The presence of a visual-auditory form suggests that CBS may represent a broader sensory deprivation phenomenon. Increased clinician awareness is essential to prevent misdiagnosis and unnecessary treatment.

References

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