Understanding Neuropsychiatric Fluctuations in Parkinson's Disease: From Mechanisms to Management

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Abstract
Background: In patients with fluctuating Parkinson's disease (PD), treatment decisions predominantly focus on motor complications, whereas neuropsychiatric symptoms are often regarded as static. Neuropsychiatric fluctuations (NPF), however, are frequent, can rival or exceed motor symptoms in their impact on quality of life, and may predispose patients to persistent neuropsychiatric complications if left unrecognized. Objective: To propose a structured approach to the definition, mechanistic underpinnings, assessment, and management of NPF. Methods: Narrative review of clinical and mechanistic studies on NPF in patients with fluctuating PD, complemented by the authors’ clinical and research experience in the recognition and management of these phenomena. Findings were synthesized to provide a structured overview of their clinical characteristics, underlying mechanisms, assessment, and management, and to inform the proposed framework. Results: NPF are characterized by intradiurnal changes in mood, motivation, anxiety, and cognition that closely track the short‐term pharmacodynamics of dopaminergic therapy, reflecting transitions between relative dopaminergic deficiency during OFF periods and excessive dopaminergic stimulation during peak dose states. Converging clinical and mechanistic evidence supports dynamic fluctuations in dopaminergic tone within limbic and associative circuits as a key driver of NPF, whereas other neurotransmitter systems may also modulate their clinical expression. Recognition of NPF remains difficult because, unlike motor complications, they are less amenable to objective observation and quantification, patient self‐report is often limited by impaired insight, and commonly used PD rating scales fail to capture these phenomena. Consequently, effective management requires early identification and therapeutic strategies aimed at stabilizing dopaminergic tone within mesolimbic and mesocortical circuits. Timely detection and proactive treatment adjustments may help limit the progression and severity of neuropsychiatric complications over time. Conclusions: To move beyond a motor‐centric paradigm, the field requires consensus definitions, improved understanding of underlying mechanisms, validated assessment instruments, and clinical trials that prioritize NPF as primary outcomes.

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