Objective: Within a single center, describe individuals with parkinsonism who develop seizures and vice versa based on epilepsy and movement disorders evaluation.

Background: While neurodegeneration is a known risk factor for late-onset epilepsy, there is burgeoning evidence of risk with parkinsonism. Prior studies, drawing largely from primary care and insurance databases, suggest a nearly twofold bidirectional risk of seizures and Parkinson’s Disease (PD), even while controlling for confounders such as dementia and valproic acid (VPA) exposure.

Method: Retrospective case series of patients seen between 1/2018-12/2025 by both an epileptologist and movement disorders specialist with diagnoses of both seizure and parkinsonism.

Results: Among eleven total patients, five developed parkinsonism first (median age 69), followed by seizure onset a median of 58 months later. Diagnoses included PD Dementia (n=2), Dementia with Lewy Bodies (DLB, n=1), idiopathic PD (n=1), and Multiple System Atrophy (n=1). At seizure onset, median MDS-UPDRS was 49.5 and Hoehn &Yahr stage was four. None had provoked or intractable seizures, nor status epilepticus. The five patients with pre-existing seizures were all exposed to VPA for at least six months prior to parkinsonism onset. Diagnoses included drug-induced parkinsonism (n=1), drug-induced parkinsonism followed by re-emergent idiopathic parkinsonism off VPA (n=2), and DLB (n=2). There was one case of concurrent onset of DLB and left temporal lobe epilepsy who had both Agent Orange and Camp Lejeune exposures. All eleven had evidence of cognitive impairment: six on formal neuropsychological testing, four on brief screening tests, and one with clinically significant impairment without documented testing.

Conclusion: In this small sample of individuals with coexisting parkinsonism and epilepsy, Lewy Body Dementia (PDD or DLB) was the most common diagnosis. The overwhelming presence of cognitive impairment in all cases raises the question of whether seizures and parkinsonism share unique co-pathology in dopaminergic degeneration, cortical alpha-synuclein spread, or epileptogenicity of concurrent cortical amyloid. Further studies into their relationship with shared risk factors and mimics could impact identification and management of both parkinsonism and epilepsy, including medications with dual motor and antiseizure benefit and anticipatory guidance for patients and families.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/bidirectional-associations-between-seizures-and-parkinsonism-a-retrospective-case-series/