Visual hallucination in patients with sensory deprivation: Charles Bonnet syndrome?

Introduction Some patients, after brain or peripheral injuries, lose a sensory function, such as sight or hearing, but paradoxically experience complex hallucinations related to the function they have lost. It is known that this phenomenon may appear with injuries at any level in the visual pathway, especially in the retina. Objective To review the existent bibliography on the Charles Bonnet syndrome to establish the state of the art with regards to this phenomenon. Method The databases PubMed and PsychInfo were searched for articles containing the following keywords: Charles Bonnet syndrome; visual hallucinations; peduncular hallucinosis; Charles Bonnet; sensory deprivation. We included those related to the subject. We also included the classic texts referring to this phenomenon and the articles mentioned in the literature. Results In the present study, we describe the history of Charles Bonnet syndrome, clinical presentation, risk factors, diagnostic criteria, treatment employed, similar conditions and the theories seeking to explain it. Discussion and conclusion To date, the diagnostic criteria for Charles Bonnet syndrome remain controversial, especially those Concerning the absolute preservation of insight as a sine qua non factor to establish the diagnosis. Conclusion: Described since the 18th century, the Charles Bonnet syndrome corresponds to the prototype of visual hallucinations in patients with visual deprivation, although, according to the present review, its phenomenology is vast, remaining unclear if, it corresponds to the prototype of hallucinations with preserved insight.