Objective: Identify alterations associated with minor hallucinations (MH) and their role in cognitive decline in patients with Parkinson’s disease (PD) by merging electroencephalography (EEG) with neuropsychiatric interviews and neuropsychological examinations

Background: Patients with PD are prone to hallucinations and cognitive decline (Ffytche et al., 2017). Formed visual hallucinations (VH) are frequent and prominent symptoms that predict PD dementia (PDD), increased mortality,  earlier home placement and have been associated with altered oscillations measured with EEG. While VH generally occur late in the disease, growing evidence suggest that MH anticipate VH and cognitive decline, by several years, making them appealing candidates for the early identification of early cognitive decline

Method: We investigated whether MH are associated with specific alterations in oscillatory activity and whether such changes are associated with specific neuropsychological deficits, potentially indicating a more severe form of PD. With this aim, we combined a model-driven EEG approach to measure periodic and aperiodic properties of resting-state EEG data with in-depth neuropsychiatric interviews to investigate hallucinations and 5-years longitudinal neuropsychological examinations to determine cognitive functions in 75 patients

Results: We report alterations in frontal theta frequency in PD patients with MH and show that these changes were associated with cognitive deficits, but were absent in PD patients without MH. By integrating the results of neuropsychiatric interviews with EEG and with neuropsychological data, we found that PD patients with MH are characterized by enhanced frontal theta oscillatory activity and that this enhanced oscillatory power is associated with lower cognitive scores in frontal-subcortical functions. Longitudinal data show that patients with MH have a more rapid cognitive decline, and that the severity of this decline is anticipated by the frontal theta impairment measured during the first assessment

Conclusion: Our results suggest that patients at higher risk for a more severe form of the disease with cognitive decline and dementia can be identified by this triad of frontal theta, frontal-subcortical cognitive decline, and MH. This would not have been possible by using each of these measures alone or in other combinations

References: Dominic H Ffytche, Byron Creese, Marios Politis, K Ray Chaudhuri, Daniel Weintraub, Clive Ballard, Dag Aarsland, The psychosis spectrum in Parkinson disease, Nat Rev Neurol. 2017 Feb;13(2):81-95

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MDS Abstracts - https://www.mdsabstracts.org/abstract/early-cognitive-decline-in-parkinsons-disease-is-anticipated-by-enhanced-frontal-theta-oscillations-and-minor-hallucinations/