Abstract
Visual hallucinations (VH) represent one of the core features in discriminating dementia with Lewy bodies (DLB) from Alzheimer’s Disease (AD). Previous studies reported that in DLB patients functional alterations of the parieto-occipital regions were correlated with the presence of VH. The aim of our study was to assess whether morphological changes in specific cortical regions of DLB could be related to the presence and severity of VH. We performed a cortical thickness analysis on magnetic resonance imaging data in a cohort including 18 DLB patients, 15 AD patients and 14 healthy control subjects. Relatively to DLB group, correlation analysis between the cortical thickness and the Neuropsychiatric Inventory (NPI) hallucination item scores was also performed. Cortical thickness was reduced bilaterally in DLB compared to controls in the pericalcarine and lingual gyri, cuneus, precuneus, superior parietal gyrus. Cortical thinning was found bilaterally in AD compared to controls in temporal cortex including the superior and middle temporal gyrus, part of inferior temporal cortex, temporal pole and insula. Inferior parietal and supramarginal gyri were also affected bilaterally in AD as compared to controls. The comparison between DLB and AD evidenced cortical thinning in DLB group in the right posterior regions including superior parietal gyrus, precuneus, cuneus, pericalcarine and lingual gyri. Furthermore, the correlation analysis between cortical thickness and NPI hallucination item scores showed that the structural alteration in the dorsal visual regions including superior parietal gyrus and precuneus closely correlated with the occurrence and severity of VH. We suggest that structural changes in key regions of the dorsal visual network may play a crucial role in the physiopathology of VH in DLB patients.
Highlights
Dementia with Lewy bodies (DLB) is the second most common form of dementia in the elderly after Alzheimer’s Disease (AD)
Dopamine-transporter hypocaptation in the caudate nuclei at SPECT-DAT scan was observed in all DLB patients, and it was bilateral in 12 patients
AD and DLB patients exhibited no differences on global test of cognition (CDR, Dementia Rating scale-2 (DRS-2), Mini Mental State Examination (MMSE))
Summary
Dementia with Lewy bodies (DLB) is the second most common form of dementia in the elderly after Alzheimer’s Disease (AD). Despite the precise nosological relationship between DLB and AD remains uncertain, persistent visual hallucinations (VH) along with fluctuations in cognitive function and parkinsonism represent the core feature in discriminating DLB from AD and other dementias [1]. Abnormalities within the ventral visual stream, revealed by white matter damage to the inferior longitudinal fasciculus [3] and by increased Lewy body pathology in the temporal lobe [4,5], were reported in DLB patients with VH compared to those without VH, supporting the role of a bottom-up dysfunction. Increased atrophy [6] and Lewy body pathology [5] within frontal lobes were observed in hallucinating DLB in comparison with non-hallucinating DLB patients, supporting a top-down mechanism in the genesis of VH
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