Insulin Resistance in Multiple System Atrophy

This study is investigating whether people with multiple system atrophy (MSA) — a rare brain disorder affecting movement and automatic body functions — have problems with insulin resistance (the body not responding properly to insulin), and whether this is linked to changes in the brain. **You may be eligible if:** - You have a diagnosis of "possible" or "probable" multiple system atrophy (MSA) - You are over 30 years old - You are covered by the national health system (in France) - Healthy volunteers over 30 without neurological disorders are also eligible for comparison **You may NOT be eligible if:** - You have diabetes - You take corticosteroids, estrogens, atypical antipsychotics, or antiretroviral medications - You are pregnant or breastfeeding - Your score on a brief memory test (MoCA) is very low (21 or below) - You cannot have an MRI Talk to your doctor to see if this trial is right for you.