Recent advances in structural and functional imaging and in neuropathology have revealed distinctive changes in multiple system atrophy (MSA), and now can be added to current diagnostic guidelines, which utilize clinical criteria alone. This is a proposal to plan, develop and convene a consensus conference on the diagnosis of MSA and create a new set of diagnostic criteria incorporating recent advances in imaging and neuropathology. A Steering Committee has selected the participants from a large group of internationally recognized experts in the specific manifestations of MSA. Participants were selected based upon their expertise in the diagnosis of MSA, and special efforts were made to include women and minorities. In advance of the conference, the Steering Committee will divide the participants into five groups based upon their specific expertise, appoint a chair for each group, and give each group the task of developing draft consensus guidelines from its unique perspective. The groups include neuropathology, imaging, and the parkinsonian, cerebellar and autonomic manifestations of MSA. Upon receipt of these draft guidelines, the Steering Committee will integrate them and develop a unified draft consensus document for consideration at the conference. The conference will be convened in Boston on April 26 and 27, 2007 in association with the annual meeting of the American Academy of Neurology. Utilizing consensus methodology, the participants will develop new guidelines for the clinical diagnosis of MSA based upon the draft from the Steering Committee. The results will be incorporated into abstracts for appropriate clinical meetings and a full manuscript will be developed for publication in a prominent neurological journal. MSA, Parkinson's disease and the ataxias are within the province of interest of NINDS, which funds a program project on MSA and numerous grants in the remaining areas. Three of the participants in the current proposal are investigators in the NINDS Program Project on MSA. Relevance to public health: MSA is a progressive neurodegenerative disorder that is often mistaken for Parkinson's disease. Accurate early diagnosis is important for medical therapy of many of the treatable features of MSA and for selecting subjects for clinical trials of new medications. This conference will assist with early diagnosis by developing new guidelines for diagnosis using newly available imaging and neuropathological criteria. [unreadable] [unreadable] [unreadable]