This study explores nerve damage in Multiple System Atrophy (MSA) and how a protein called tau is involved in another illness, Progressive Supranuclear Palsy (PSP). MSA is a disease affecting the brain, and synapses are points where nerve cells connect and communicate. Researchers will use a special kind of imaging called Positron Emission Tomography (PET) to check how synapses are doing in MSA patients.

• Participants will have clinical visits, PET scans, and an optional spinal fluid test.
• The study requires stable medical conditions for at least 30 days before starting.
• Comparisons will involve 16 PSP patients and a subgroup of 10 MSA patients for additional imaging.

Eligibility includes males and females aged 45-80 years, with specific criteria for each condition. The study hopes to better understand these diseases and aid in future treatments.