Abstract
Multiple system atrophy (MSA) is a progressive neurodegenerative disease characterized by symptoms of parkinsonism, cerebellar ataxia, autonomic dysfunction, urogenital dysfunction, and corticospinal tract involvement. The disease is classified into two main subtypes: the cerebellar-predominant subtype (MSA-C) and the parkinsonian-predominant subtype (MSA-P). Classification as MSA-P or MSA-C depends on whether parkinsonian or cerebellar features predominate at the time of evaluation. In 2008, experts on MSA reached consensus on the second consensus statement on diagnostic criteria for MSA, developed by the American Academy of Neurology and the American Autonomic Society. However, when applying these consensus criteria, the sensitivity for diagnosing "probable" MSA was only 18%, and for "possible" MSA was 41%, at the first clinical visit. For this reason, in April 2022, the International Parkinson and Movement Disorder Society (MDS) issued new diagnostic criteria for MSA, which remain largely based on the core 2008 criteria while incorporating additional supportive features to enable earlier diagnosis with higher sensitivity. Under the new MDS 2022 criteria, MSA is classified into four diagnostic certainty levels: neuropathologically "established" MSA, clinically "established" MSA, clinically "probable" MSA, and "possible prodromal" MSA. Current treatment for MSA remains symptomatic. Disease-modifying or progression-slowing therapies are still under investigation through clinical trials.
