Objective: This study aims to identify pre-treatment indicators for Parkinson’s disease (PD) patients who respond well to monoamine oxidase type B inhibitors (MAOBIs). ​​​​​

Background: MAOBIs, an initial treatment option for PD, enhance endogenous dopamine activity by inhibiting dopamine metabolism. Since endogenous dopamine affects motor function, cognition, mental state, and blood pressure, treatment response may be predicted based on patient characteristics. While MAOBIs are generally considered less effective than levodopa or dopamine agonists, their motor symptom efficacy varies among cases. Early MAOBI treatment may reduce levodopa dosage, potentially mitigating long-term complications.

Method: We retrospectively analyzed drug-naïve PD patients diagnosed between February 2023 and November 2024. Baseline assessments included neuropsychiatric tests (MMSE, MoCA-J, FAB, BDI) and cardiovascular autonomic function evaluations (¹²³I-MIBG cardiac scintigraphy, blood pressure and heart rate changes during the head-up tilt test, and plasma norepinephrine and vasopressin levels in supine and standing positions). Correlation coefficients between these baseline characteristics and motor symptom improvement (MDS-UPDRS Part III) were analyzed at 10 weeks after treatment initiation.

Results: Among 44 sporadic PD cases, 21 received MAOBIs (selegiline: 13, rasagiline: 8), 18 received levodopa, and 5 received dopamine agonists. Motor improvement with MAOBIs correlated negatively with blood pressure variability in the head-up tilt test (r=−0.62, p<0.01) and positively with H/M ratios in early (r=0.52, p<0.05) and delayed (r=0.52, p<0.05) myocardial MIBG scintigraphy. The washout rate showed a negative correlation (r=−0.45, p<0.05). Plasma norepinephrine levels correlated positively with bradykinesia improvement in both supine (r=0.56, p<0.05) and standing (r=0.54, p<0.05) positions

Conclusion: Patients with less orthostatic hypotension and preserved postganglionic cardiac sympathetic function were more likely to benefit from MAOBIs. Their MAO-A inhibitory effect may suppress norepinephrine metabolism, enhancing motor function via dopamine activation. Therefore, PD patients with mild orthostatic hypotension and mild MIBG myocardial scintigraphy abnormalities, where endogenous norepinephrine is retained, may experience greater motor symptom improvement with MAOBIs.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/investigation-of-baseline-factors-associated-with-a-favorable-response-to-initial-mao-b-inhibitor-treatment-in-parkinsons-disease/