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Complex visual hallucinations (Charles Bonnet syndrome) in the hemianopic visual field following occipital infarction

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Abstract

Charles Bonnet syndrome is characterised by the occurrence of complex visual hallucinations in the presence of normal cognition in elderly individuals. It commonly happens following conditions where there has been a profound loss of vision or interruption of visual input into the occipital cortex. It is important to distinguish this largely innocuous condition from psychiatric conditions that exist in the same age group. This article describes a rare variant of this condition where such hallucinations occur in the hemianopic visual field of a patient with an occipital infarct whose visual acuity is largely unimpaired. The article details the various conditions where this phenomenon has been experienced; the theories that have been postulated for its aetiology and the treatment options. The variations of this case from the commonly observed scenarios are highlighted questioning previously held convictions as well as providing an insight into the widening spectrum of the phenomenon as more cases are described. The article hopes to raise awareness of this condition, which is much commoner than perceived by healthcare practitioners, as most patients in that age group are reluctant to be forthcoming with their symptoms for fear of being diagnosed with a psychiatric disorder.

Introduction

Complex visual hallucinations with insight (Charles Bonnet syndrome) have been reported following profound visual loss in conditions like age-related macular degeneration (AMD) or even enucleation as well as following intracranial surgical procedures where the visual pathway is disrupted resulting in a decreased visual sensory input into the cortex. We report a case of Charles Bonnet Syndrome (CBS) with symptoms in the hemianopic field following an occipital lobe infarct.

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Case report

A 74-year-old male with a history of Type 2 diabetes, ischaemic heart disease, coronary artery bypass grafting, carotid endarterectomy (left), bronchial asthma and left hemiparesis from a previous cerebrovascular accident presented with a loss of vision on the right side happening one morning together with a sensation of flushing and mild giddiness. He was admitted and assessed. He was found on initial assessment to have right homonymous hemianopia and no other neuro deficit apart from the

Discussion

Charles Bonnet described in 1769 the visual hallucinations of his grandfather who was blind due to cataracts [1]. Georges de Morsier in 1936 defined CBS as formed visual hallucinations in the psychologically normal elderly patient in association with eye disease, although he denied that eye disease was the cause for the hallucinations. In a much later review article published in 1967, he omitted eye disease from this definition stressing merely on old age and absence of a mental disorder [2].

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