[Visual hallucinations: the Charles Bonnet syndrome].
The Charles Bonnet syndrome (CBS) commonly designates visual hallucinations (VH) occurring in visually impaired patients. However, there is no consensual definition. The existence of an ophthalmic disease and the absence of cognitive impairment are mandatory or not according to the proposed diagnostic criteria. CBS affects 12 to 15% of visually impaired patients. VH are often repetitive and stereotyped, elementary or complex, involving human figures in most cases. The patients had full insight of the unrealistic character of their VH. The main risk factors are old age and severe visual impairment. Functional imagery studies showed that the VH of SCB correlate with cerebral activity in ventral extrastriate visual cortex and that the hallucinations reflect the functional specializations of this region. This activity could represent release phenomena due to deafferentation of the visual associative cortical areas. No systematic therapeutic trial has been performed. Anticonvulsivant drugs may help in some instances. However, reassurance and explanations are sufficient in most cases. The VH in the hemianopic field after a stroke probably share pathophysiologic mechanisms with CBS. Finally, visual impairment appear as a non specific risk factor for VH in some conditions such as late paraphrenia and some neurodegenerative diseases such as Alzheimer's disease or Parkinson's disease.
Fénelon
Gilles
G
Service de neurologie, Hôpital Henri Mondor, Créteil. gfenelon@wanadoo.fr
D006212:Hallucinations / Q000453:epidemiology / Q000523:psychology*; D006801:Humans; D019636:Neurodegenerative Diseases / Q000150:complications; D015995:Prevalence; D012307:Risk Factors; D020521:Stroke / Q000150:complications; D013577:Syndrome; D014786:Vision Disorders