Postural Instability in Progressive Supranuclear Palsy

Inclusion Criteria: 1. Diagnosis of probable or possible PSP as defined by the National Institute of Neurological Disorders and Stroke and Society for Progressive Supranuclear Palsy (NINDS-SPSP) diagnostic criteria. 2. Be able to ambulate and stand unassisted for 5 minutes 3. Be able to cooperate with gait and balance testing 4. Be able to give informed consent. Exclusion Criteria: 1. Cannot exhibit behavior or have dementia that precludes participation in the protocol 2. Cannot have medical or orthopedic illness that, in the investigator's opinion, would impact the patient's postural control or ability to participate in the study.