The Non-Motor Symptoms Scale in Parkinson's disease: Validation and use

The Non-Motor Symptoms Scale (NMSS) was developed and validated in 2007 as the first instrument for the comprehensive assessment of a range of non-motor symptoms in Parkinson's disease (PD). Thirteen years have elapsed since its introduction and extensive international validation with good psychometric attributes has been carried out. Here, we review the validation data of the NMSS and its cross-validity with other scales, and describe the key evidence derived from use of the NMSS in clinical studies. To date, over 100 clinical studies and trials have made use of it as an outcome measure, showing consistent and strong correlations between NMSS burden and health-related quality of life measures. Moreover, the scale has shown to be capable of detecting longitudinal changes in non-motor symptoms, where studies have shown differential changes over time of several of the NMSS domains. The scale has become a key outcome in several randomized clinical trials. Highlighting the prevalence and importance of non-motor symptoms to quality of life in patients with PD, the development of NMSS has also been useful in signposting clinical and biomarker based research addressing non-motor symptoms in PD.