Cognition, hallucination severity and hallucination-specific insight in neurodegenerative disorders and eye disease

Abstract

Introduction: Hallucinations occur across neurodegenerative disorders, with increasing severity, poorer cognition and impaired hallucination-specific insight associated with worse outcomes and faster disease progression. It remains unclear how changes in cognition, temporal aspects of hallucinations, hallucinationspecific insight and distress relate to each other. Methods: Extant samples of patients experiencing visual hallucinations were included in the analyses: Parkinson's Disease (n = 103), Parkinson's Disease Dementia (n = 41), Dementia with Lewy Bodies (n = 27) and Eye Disease (n = 113). We explored the relationship between factors of interest with Spearman's correlations and random-effect linear models. Results: Spearman's correlation analyses at the whole-group level showed that higher hallucination-specific insight was related to higher MMSE score (r s = 0.39, p < 0.001) and less severe hallucinations (r s = −0.28, p < .01). Linear mixed-models controlling for diagnostic group showed that insight was related to higher MMSE (p < .001), to hallucination severity (p = 0.003), and to VH duration (p = 0.04). Interestingly, insight was linked to the distress component but not the frequency component of severity. No significant relationship was found between MMSE and hallucination severity in these analyses. Conclusion: Our findings highlight the importance of hallucination-specific insight, distress and duration across groups. A better understanding of the role these factors play in VH may help with the development of future therapeutic interventions trans-diagnostically.

Investigation of structural brain changes in Charles Bonnet Syndrome

“…We found associations between VH severity and hippocampal volume, but not with occipital volume. In a separate study which included people with CBS, reduced insight into VH was associated with both reduced MMSE score and increased VH distress ( Montagnese et al, 2021 ). It may be that hippocampal volume is an indicator of neurodegenerative processes like AD, associated with cognitive decline.…”

Visual hallucinosis during hypoperfusion of the right occipito-temporal cortex

“…humans, animal, plants), objects, writings, abstract complex forms Complex hallucinations point to an origin in higher order visual areas Context and Chronology Onset Rapid/slow progression from simple to complex hallucinations; co-occurrence of simple and complex; other related symptoms Recording of speed progression from simple to complex hallucinations can help estimate the fluctuations in the visual brain function (diaschisis progression from lower to higher-order visual cortex) [ 10 ] Occurrence conditions Ambient luminance (low, high); sensory context (effect of other stimuli—e.g., sound, touch—on the visual hallucinations) Low ambient luminance and suppression by other stimuli (e.g. high luminance, unexpected sound, pinch) indicate a release mechanism High ambient luminance and facilitation by other sensory conditions indicate a synesthetic mechanism [ 26 ] Frequency and duration Variations in hallucination frequency since occurrence, duration of each episode and the total duration of symptoms Duration might translate increased functional connectivity between ventral-visual stream and salience network, while increased frequency, decreased functional connectivity between default mode and salience network [ 25 ] Visual field Upon steady fixation note in which part of the visual field hallucinations occur (unilateral, bilateral, central) or if they occur outside the visual field (e.g., extracampine hallucinations, autoscopic phenomena) Hallucinations usually manifest in the hemi-visual field opposite the affected hemisphere; bilateral occurrence may indicate bi-hemispheric disruptions; hallucinations outside the field of view suggest dysfunctions of the temporo-parietal junction [ 27 ] Insight Record and quantify insight during the entire duration of the hallucinatory phenomena (e.g., full/some/no insight) In elderly patients, low/ no hallucination-specific insight may point to an associated neurodegenerative disorder [ 28 ] Attributes Appearance Record patient’s impression regarding the perception of the hallucinated image—natural appearance, abnormal/dysmorphic features, sketch-like appearance Abnormal features, sketch-like appearance, abnormal size suggest dysfunction in the lateral fusiform gyrus and occipital cortex coding for face features [ 29 , 30 ] …”