Parkinson's Disease With Visual Hallucinations Is Associated With Epileptiform Activity on EEG

Abstract

Background: Visual hallucinations (VHs) in Parkinson's disease (PD) are the cardinal symptoms which declare the onset of PD psychosis (PDP). The anthropomorphic and zoomorphic VHs of PD resemble those of Charles Bonnet syndrome and temporal lobe epilepsy. In both of these disorders electroencephalography (EEG) abnormalities have been described. We therefore sought to examine whether VHs in PD were associated with similar EEG abnormalities.Methods: This retrospective observational study searched the medical records of 300 PD patients and filtered for those containing clinical 20-min scalp EEGs. Remaining records were separated into two groups: patients with reported VHs and those without. The prevalence of epileptiform discharges in the EEGs of both groups was identified.Results: Epileptiform discharges were present in 5 of 13 (38.5%) PD patients with VHs; all localized to the temporal lobe. No epileptiform discharges were observed in the EEGs of the 31 PD patients without VHs.Conclusion: The significantly high incidence of temporal lobe epileptiform discharges in PD patients with VHs as compared to those without VHs lends to the possibility of an association visual cortex epileptogenic focus. Accordingly, for treatment-refractory patients, antiepileptic drugs might be considered, as in the case of Charles Bonnet syndrome, temporal lobe epilepsy and migraine with visual aura. Future prospective studies involving larger samples and multi-center cohorts are required to validate these observational findings.

How to Use the New European Academy of Neurology/Movement Disorder Society European Section Guideline for Invasive Therapies in Parkinson's Disease

“…The underlying pathophysiology of VH in PD is still unclear 85 . Recent research has improved our understanding of the development of VH, emphasizing an association with cognitive decline and epileptiform discharges in the context of a more diffuse neurodegenerative process 85,86 . Nevertheless, dopaminergic medication is still the most important provoking factor for VH 84 .…”

Subclinical Epileptiform Activity in Dementia with Lewy Bodies

“…One explanation for the increased spike frequency could be depositions of α‐synuclein, which has been shown to induce network excitability in transgenic mouse models 31 that can escalate into seizure activity 32 . In addition, one study found an association between the densities of Lewy bodies in the temporal lobes and visual hallucinations, 12 and visual hallucinations have been linked to IED in the temporal lobes in patients with Parkinson's disease 13 . However, because of a high frequency of amyloid deposition in DLB, 33,34 it is also possible that AD related pathology leads to IED in DLB patients (ie, that amyloid is the common denominator leading to IED) or that the neurodegenerative process per se leads to IED.…”

“…32 In addition, one study found an association between the densities of Lewy bodies in the temporal lobes and visual hallucinations, 12 and visual hallucinations have been linked to IED in the temporal lobes in patients with Parkinson's disease. 13 However, because of a high frequency of amyloid deposition in DLB, 33,34 it is also possible that AD related pathology leads to IED in DLB patients (ie, that amyloid is the common denominator leading to IED) or that the neurodegenerative process per se leads to IED. However, studies in transgenic mouse models have found that α-synuclein aggregation alone is sufficient to cause network hyperexcitability.…”

“…Although atrophy of the temporal lobes is generally not as pronounced in DLB as in AD, 11 one study has suggested that a higher density of Lewy bodies is present in the temporal lobes 12 . Furthermore, in Parkinson's disease visual hallucinations may be related to IED originating from the temporal lobes 13 …”

“…12 Furthermore, in Parkinson's disease visual hallucinations may be related to IED originating from the temporal lobes. 13 Because of the possible clinical relevance of detecting IED, there is a need for accessible and dependable EEG monitoring in an outpatient setting. One method is ear-EEG 14 where the EEG signals are recorded from electrodes placed within a customized earpiece inserted into each ear and is associated with little interference of everyday life.…”