The elephant in the room: understanding the pathogenesis of Charles Bonnet syndrome

Abstract

Purpose Charles Bonnet syndrome (CBS) is a syndrome characterised by complex visual hallucinations in individuals who are cognitively normal, though often elderly and visually impaired. Although first described over 250 years ago, the condition remains poorly understood and difficult to treat. Recent findings Our understanding of CBS pathogenesis has advanced little since it was first described, and much of the recent literature consists of case studies strikingly similar to the first published account of CBS. However, imaging studies have provided some indication as to the cortical areas implicated in the genesis of complex visual hallucinations, and the existence of similar hallucinatory syndromes in other sensory modalities suggests a common underlying mechanism. Summary This review begins by describing what is currently known about CBS, focusing on epidemiology, clinical presentation and diagnosis. It then explores potential starting points for better understanding the pathogenesis of CBS, namely the existence of similar conditions in other sensory modalities and the reproduction of complex visual hallucinations in sensory deprivation scenarios. Finally, it discusses how CBS should be approached in clinical practice.

Exacerbation of visual hallucinations in Charles Bonnet syndrome due to the social implications of COVID-19

“…For example, one participant described being followed by a shadowed figure whenever they were walking, while others described feelings of claustrophobia due to being trapped by encroaching plants and foliage. This finding supports previous theories that sensory deprivation, as a result of social isolation, is associated with visual hallucinations in CBS 2 19 20. However, living conditions do not fully explain hallucination phenomenology as previous findings identify a higher prevalence of CBS among married individuals as well as those cohabiting 27.…”

“…There was a statistically significant association between age and loneliness, whereby those who were lonelier during the pandemic were, on average, older than those with no changes in feelings of loneliness (mean age 73.3±17 vs 60.2±19 years, Kruskal-Wallis test; p=0.03). In addition, those reporting a change in their emotional reaction to hallucinations through the pandemic were, 20 Treatment pathways in persistent cases include patient counselling and cognitive-behavioural therapy, with a theoretical basis for pharmacological modification of cholinergic, GABAergic, serotonergic or dopaminergic systems, or reduction of cortical excitability. 21 An important health priority for people with CBS will be to mitigate the impact of the lockdown and subsequent isolation, ensuring they remain socially connected.…”

“…People with CBS have experienced changes in visual hallucination phenomenology during the national lockdown associated with the COVID-19 pandemic. There is no established cure for CBS; however, patient education and reassurance play a vital role in improving quality of life 20. Treatment pathways in persistent cases include patient counselling and cognitive–behavioural therapy, with a theoretical basis for pharmacological modification of cholinergic, GABAergic, serotonergic or dopaminergic systems, or reduction of cortical excitability 21.…”

Cones in ageing and harsh environments: the neural economy hypothesis

“…Potential vision from surviving cones may not always be a positive outcome for a patient, as this imperfect visual input may be a negative factor in patients who are older and have AMD. Large numbers of patients experience visual hallucinations, known as Charles Bonnet syndrome …”

Šarlio Bonė (Charles Bonnet) Sindromas

“…Vieni autoriai CBS prilygina fantominiam galūnių skausmui ir jį vadina "fantominės regos sindromu", o jo atsiradimą aiškina atpalaiduojamuoju reiškiniu (angl. release phenomenon) [5]. Remiantis juo,…”