Congratulations to Dr. Michael Okun on the publication of “A Statement of the MDS on Biological Definition, Staging, and Classification of Parkinson’s Disease,” which appears in the December 2023 issue of Movement Disorders.
Disease staging is an important tool in both clinical research and medical practice because it allows for an unequivocal allocation of individuals into groups of shared biomedical characteristics along a specific disease trajectory. The disease staging approach comes from the field of cancer, in which the disease’s extent and chronological progression were systematically described as early as the 1930s.1 In this case, a staging system was developed to describe—for each particular type of cancer—the primary tumor, nodes, and metastasis (TNM) at various sites.2 Cancer staging is defined solely by anatomical and biological features, and the symptoms that the patient experiences are not included. The TNM system has been used for several decades and is well-validated in its ability to establish prognosis and direct treatment protocols. With the rapid expansion of new data and advances in the field of neurodegeneration, there has been a growing interest in developing a similar format for disease staging and/or classification in Parkinson’s disease (PD).