Investigation of structural brain changes in Charles Bonnet Syndrome.

BACKGROUND AND OBJECTIVES: In Charles Bonnet Syndrome (CBS), visual hallucinations (VH) are experienced by people with sight loss due to eye disease or lesional damage to early visual pathways. The aim of this cross-sectional study was to investigate structural brain changes using magnetic resonance imaging (MRI) in CBS. METHODS: Sixteen CBS patients, 17 with eye disease but no VH, and 19 normally sighted people took part. Participants were imaged on a 3T scanner, with 1 mm resolution T1 weighted structural imaging, and diffusion tensor imaging with 64 diffusion directions. RESULTS: The three groups were well matched for age, sex and cognitive scores (MMSE). The two eye disease groups were matched on visual acuity. Compared to the sighted controls, we found reduced grey matter in the occipital cortex in both eye disease groups. We also found reductions of fractional anisotropy and increased diffusivity in widespread areas, including occipital tracts, the corpus callosum, and the anterior thalamic radiation. We did not find any significant differences between the eye disease participants with VH versus without VH, but did observe a negative association between hippocampal volume and VH severity in the CBS group. DISCUSSION: Our findings suggest that although there are cortical and subcortical effects associated with sight loss, structural changes do not explain the occurrence of VHs. CBS may relate instead to connectivity or excitability changes in brain networks linked to vision.

Visualization of hypermetabolism in the ventral visual pathway by FDG-PET in the Charles Bonnet syndrome.

A 74-year-old man presented with complex visual hallucinations with a left inferior quadrantanopia. The characteristics of the visual hallucinations met the criteria for the Charles Bonnet syndrome. Brain magnetic resonance imaging (MRI) revealed a right occipital falx meningioma. Fusion images of gadolinium-enhanced MRI and 18F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) of the brain demonstrated hypometabolism in the right primary and secondary visual cortices, and an ipsilateral hypermetabolism in a focal area of the medial aspect of the secondary visual cortex as well as the lateral part of the ventral visual pathway. These findings imply that hyperactivation of the ventral visual pathway, especially the lateral aspect of the ventral occipitotemporal cortex, may be related to the face hallucinations in this patient. This case highlights features of FDG-PET that can explain the pathophysiology of the Charles Bonnet syndrome.

Resting-state functional connectivity and cortical thickness characterization of a patient with Charles Bonnet syndrome.

Charles Bonnet syndrome (CBS) is a rare condition characterized by visual impairment associated with complex visual hallucinations in elderly people. Although studies suggested that visual hallucinations may be caused by brain damage in the visual system in CBS patients, alterations in specific brain regions in the occipital cortex have not been studied. Functional connectivity during resting-state functional magnetic resonance imaging (rs-fMRI; without hallucinations) in CBS patients, has never been explored. We aimed to investigate brain structural and functional changes in a patient with CBS, as compared with late blind (LB) and normally sighted subjects. We employed voxel-based morphometry and cortical thickness analyses to investigate alterations in grey matter characteristics, and rs-fMRI to study changes in functional brain connectivity. Decreased grey matter volume was observed in the middle occipital gyrus and in the cuneus in the CBS patient, and in the middle occipital gyrus and in the lingual gyrus within LB subjects, compared to their respective control groups. Reductions in cortical thickness in associative and multimodal cortices were observed in the CBS patient when comparing with LB subjects. The precuneus exhibited increased functional connectivity with the secondary visual cortex in the CBS patient compared to the controls. In contrast, LB patients showed decreased functional connectivity compared to sighted controls between the DMN and the temporo-occipital fusiform gyrus, a region known to support hallucinations. Our findings suggest a reorganization of the functional connectivity between regions involved in self-awareness and in visual and salience processing in CBS that may contribute to the appearance of visual hallucinations.

FDG-PET Scanning Shows Distributed Changes in Cortical Activity Associated with Visual Hallucinations in Eye Disease.

BACKGROUND AND OBJECTIVE: Charles Bonnet Syndrome (CBS) has been defined as complex visual hallucinations (CVH) due to visual loss. The underlying mechanism of CBS is not clear and the underlying pathophysiology of the visual hallucinations in CBS patients and pure visually impaired patients is still not clear. METHODS: In our study, we have scanned three patients with eye disease and CBS (VH+) and three patients with eye disease without CBS (VH-) using FDG-PET. RESULTS: Our results showed underactivity in the pons and overactivity in primary right left visual cortex and inferior parietal cortex in VH- patients and underactivity in left Broca, left inf frontal primary visual cortex and anterior and posterior cingulate cortex in VH+ patients relative to the normative 18FFDG PET data that was taken from the database consisting of 50 age-matched healthy adults without neuropsychiatric disorders. CONCLUSION: From this distributed pattern of activity changes, we conclude that the generation of visual hallucination in CBS is associated with bottom-up and top-down mechanism rather than the generally accepted visual deafferentation-related hyperexcitability theory.

Charles Bonnet syndrome versus Occipital Epilepsy, a diagnostic challenge.

Charles Bonnet Syndrome (CBS) is a disorder with visual deficit and complex recurrent visual hallucination in conscious patients, described for the first time by Charles Bonnet. It has been found in association with variable pathologic conditions of the eyes, central visual pathways and occipital lobe. Occipital lobe lesion is an important cause of visual field deficit associated with elementary simple hallucinations, whereas complex hallucinations are related to occipitotemporal and occipitoparietal visual association neocortex damage.