Non-motor fluctuations in Parkinson's disease: underdiagnosed, yet important.

Non-motor fluctuations (NMF) in Parkinson's disease (PD) significantly affect patients' well-being. Despite being identified over two decades ago, NMF remain largely under-recognized, under-treated, and poorly understood. While they are often temporally associated with motor fluctuations (MF) and can share common risk factors and pathophysiologic mechanisms, NMF and MF are currently considered distinct entities. The prevalence and severity of NMF, often categorized into neuropsychiatric, sensory, and autonomic subtypes, vary significantly across studies due to the heterogeneous PD populations screened and the diverse evaluation tools applied. The consistent negative impact of NMF on PD patients' quality of life (QoL) underscores the importance of further investigation via focused and controlled studies, validated assessment instruments and novel digital technologies. High-quality research is essential to illuminate the complex pathophysiology and clinical nuances of NMF, ultimately enhancing clinicians' diagnostic and treatment options in routine clinical practice.