Objective: To explore, in patients with newly diagnosed Parkinson’s disease (PD), grey matter volume (GMV) differences at baseline in those participants who will develop hallucinations during the first 5 years of evolution. We also aimed to analyze if this subgroup has a different pattern of atrophy progression in a 12-month period.

Background: The development of visual hallucinations in patients with PD is associated with worse cognitive outcome and poor prognosis [1]. Determining structural imaging biomarkers associated with development of hallucinations may allow for the earlier identification of patients at risk.

Methods: One hundred and thirty-one ‘de novo’, drug-naïve PD patients from the Parkinson’s Progression Marker Initiative (PPMI) with available 3T MRI scan and without hallucinations at baseline, were included in the analysis. One hundred and eight of these patients had a 12-month follow-up scan. According to MDS-UPDRS I “Hallucinations and psychosis”, patients were classified as those who developed hallucinations in the follow-up (n=40) and those who did not (n=85). Groups were matched for age, education, cognition and motor status. SPM12 was used to compare GMV between both groups at baseline and longitudinal GMV loss in 1 year. Significance was set at p<0.01.

Results: From the overall sample, 40 patients developed hallucinations during the 5-year follow-up (n=5 during the first year). These patients showed significant differences in GMV at baseline in right peristriate visual cortex (BA19), right fusiform gyrus (BA37), right angular gyrus (BA39), right superior parietal lobe (BA7) and bilateral primary visual cortex (BA17). An increased 12-month GMV loss was seen in those patients who will develop hallucinations, involving bilateral parahippocampal gyrus (BA36), left fusiform gyrus (BA 37), right inferior temporal gyrus (BA20), right precentral gyrus (BA1) and left middle occipital gyrus (BA18) [figure 1].

Conclusions: Our results reveal that development of hallucinations is preceded by more extensive GMV loss and increased rate of atrophy in visual occipital and posterior temporal regions. Volumetric changes in these regions have been previously associated with well-structured hallucinations [2], and it seems that these areas could be affected even before the appearance of the symptom. Neuroimaging data should be further explored as a potential biomarker to identify individuals at risk for hallucinations.

References: [1] Anang, J. B. et al. Predictors of dementia in Parkinson disease: a prospective cohort study. Neurology 83, 1253–1260 (2014). [2] Goldman, J.G. et al. Visuoperceptive region atrophy independent of cognitive status in patients with Parkinson’s disease with hallucinations. Brain 2014;137:849-59.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/early-cortical-signature-of-development-of-visual-hallucinations-in-de-novo-parkinsons-disease/