Objective: Characterize the subgroup of Parkinson’s Disease (PD) patients with isolated delusions.

Background: Psychotic features in patients with PD, especially delusions, usually are thought to be associated with disease progression and visual hallucinations, in a background of cognitive deterioration and dopaminergic therapy. Isolated delusions have been less frequently described and not well characterized, and seem to occur in a subgroup of PD patients that is distinct from those who develop visual hallucinations and dementia.

Method: PD patients followed by the authors between Jan 2014 – Jan 2018 at a movement disorders clinic were identified using the ICD9 code 3320. Charts were retrospectively reviewed to identify patients with isolated delusions.  Neurological and psychiatric interviews were performed, including MDS-UPDRS, MoCA, NPI and SCOPA-PC.

Results: Of 127 patients with PD, 10 (7,9%) had isolated delusions and 8 were interviewed. These patients were 3 male : 5 female, aged 66,1 (SD ± 11) years, age of onset of PD 58 years, mean duration of disease of 8 years, Hoehn & Yahr 2. Six patients had non-tremor dominant akinetic-rigid phenotype and 2 patients had tremor dominant phenotype. Levodopa equivalent dose was 530 mg and all except one were on dopaminergic agonists when delusions started. Mean MoCA score was 23. Delusions were paranoid (5) or jealousy (3) in nature. With dose reduction/interruption of dopaminergic agonists alone or with institution of antipsychotic treatment, 5 improved or resolved. At NPI we found moderate distressed caregivers (mean 3 and SD ± 1,9).

Conclusion: As described in the literature, these PD patients who developed isolated delusions were younger, in an early stage of disease progression, non demented, and there was a clear relation to dopamine agonist therapy, with remission only in a small sample. These symptoms, which can be very disruptive for family and patient, are not recognized as a treatment complication, being vastly underdiagnosed. Active screening and family involvement may be key factor to early recognition, diagnosis and treatment. A study comparing this subset of PD developing delusions to PD patients with the same disease duration is needed, in order to identify susceptibility factors.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/isolated-delusion-in-idiopathic-parkinsons-disease-particularities-in-a-subgroup-of-patients/