Objective: This study was aimed to investigate a predictive factor of refractory impulse control disorder (ICD) in patients with Parkinson’s disease (PD) who participated in a multicenter intervention trial for ICD (REIN-PD trial).

Background: Although dopamine agonist is a significant contributor to ICD development, dopamine agonist substitution with levodopa could not improve aberrant behaviors in some PD patients. If we could predict intractable ICD, we could make a therapeutic plan with a multidisciplinary approach to these individuals in advance.

Method: We conducted a case-control study using the REIN-PD database. Poor response (PR) group was defined as those who showed paradoxical increases in modified Minnesota Impulsive Disorders Interview (mMIDI) after substituting dopamine agonists with levodopa formulations in REIN-PD trial. We analyzed baseline neuropsychiatric traits of PR group in comparison to good response (GR) group to identify potential risk trait that can predict PR at 12 weeks after intervention. An extended analysis was carried out in the non-PR total REIN-PD ICD (TOTAL) group that included all dropped-out cases as well as the GR group. Finally, Receiver Operating Characteristic (ROC) curve analysis was performed to evaluate the predictive efficacy of the potential risk trait for refractory ICD.

Results: Among the 38 patients who completed dopamine agonist replacement in REIN-PD trial, we identified 15 (39.5%) PR and 20 GR patients. Baseline demographics, ICD severity, PD severity, and dopaminergic medications were indifferent between the PR and GR groups. However, PR group had distinctively high scores compared to GR group in the baseline State-Trait Anger Expression Inventory (K-STAXI) and the Obsessive-Compulsive Inventory-Revised (K-OCI-R) (36.3±11.3 vs. 27.7±5.2 and 28.9±12.8 vs. 17.8±14.2, p = 0.007 and 0.009, respectively). The baseline K-OCI-R in PR group was also significantly high when it was compared with that in TOTAL group (N=35, intention-to-treat analysis; 28.9±12.8 vs. 18.1±13.9, p = 0.009). In the ROC curve analysis, the baseline K-OCI-R showed the highest area under the curve [AUC = 0.735 (0.591-0.850)] with optimal cut-off score 22/72 in discriminating the PR from the TOTAL group.

Conclusion: Obsessive-compulsiveness may predict a poor response to dopamine agonist substitution therapy in PD patients with ICD.

References: Lee JY, Jeon B, Koh SB, Yoon WT, Lee HW, Kwon OD, Kim JW, Kim JM, Ma HI, Kim HT, Baik JS, Cho J; (REIN-PD Investigators). Behavioral and trait changes in parkinsonian patients with impulse control disorder after switching from dopamine agonist to levodopa therapy: results of REIN-PD trial. J Neurol Neurosurg Psychiatry. 2019 Jan;90(1):30-37.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/predictors-of-refractory-impulse-control-disorder-to-dopamine-agonists-substitution-therapy-in-parkinsons-disease-patients/