September 28, 2017
By Megan Brooks
NEW YORK (Reuters Health) - Loss of functional connectivity in key brain areas involved in attention and visual processing may contribute to visual hallucinations (VH) in patients with Parkinson's disease (PD), new research suggests.
The findings provide “insights into the functional substrates of VH in patients with PD and may offer future markers to predict the occurrence of VH in patients with PD,” the authors write in their report, published online September 27 in Radiology.
"Visual hallucinations in Parkinson's disease are frequent and debilitating. Our aim was to study the mechanism underlying visual hallucinations in Parkinson's disease, as these symptoms are currently poorly understood,” first author Dr. Dagmar Hepp, neurology resident at VU University Medical Center (VUMC) in Amsterdam, the Netherlands, said in a statement.
The investigators used whole-brain resting-state functional magnetic resonance imaging (fMRI) to examine connectivity patterns between different relevant brain areas in 15 PD patients with VH, 40 PD patients without VH, and 15 healthy controls.
They found that mean whole-brain functional connectivity was markedly lower in PD patients with or without VH, compared with controls. Regional decreases involving paracentral and occipital regions were evident in both PD groups.
Also, compared with controls, PD patients with VH had “widespread loss of functional connectivity, including frontal, temporal, occipital, and striatal brain regions (P<0.05 false discovery rate corrected). Functional connectivity alterations in these regions are related to cognitive impairments previously implicated in the pathophysiological mechanisms of VH in PD (eg, deficits in attention, attentional set shifting, and perception; P<0.05),” the authors report.
The findings, write Dr. Hepp and colleagues, “argue against the notion that a single specific functional brain region or network is the neural substrate of VH in PD, but rather supply further evidence for a more global loss of network efficiency, which could drive disturbed attentional and visual processing and thereby lead to VH in PD.”
In an email to Reuters Health, Dr. Hepp said, “There are no direct therapeutic implications for patient care based on our research, since our research was primarily meant to find out more about the underlying mechanism of VH in PD. However, future studies could indicate whether techniques that could stimulate the areas with decreased connectivity in PD patients with VH - i.e., the areas that communicated less with the rest of the brain - could be helpful to treat VH in PD.”
“Longitudinal research is needed to investigate whether decreased functional connectivity could indeed predict the occurrence of VH in PD,” Dr. Hepp added.
The study had no commercial funding.
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