The main objectives are to determine on one hand whether oligomeric alpha-synuclein levels are increased in MSA patients compared to controls and on other hand whether there is a good agreement between cerebrospinal fluid (CSF) and plasma levels.

Multiple system atrophy (MSA) is a rare neurodegenerative disorder which is characterized by a variable combination of parkinsonism, cerebellar dysfunction, autonomic failure, and additional signs.

No effective treatment is available. Together with PD and Lewy body dementia, MSA belongs to a group of neurodegenerative disorders, the alpha-synucleinopathies, which are characterized by the abnormal accumulation of alpha-synuclein.

The development of biological markers for the diagnosis and prognosis in MSA remains an unmet need. Such biological markers are crucial for future disease-modification and neuroprotection trials. Alpha-synuclein has a high potential for biomarker development since it constitutes the pathological hallmark feature in MSA.

The oligomeric alpha-synuclein seems to be particularly involved in abnormal protein aggregation in alpha-synucleinopathies.

The study will compare alpha-synuclein levels in CSF and plasma between patients suffering from AMS and controls who are patients requiring spinal tap without being affected by a neurodegenerative disorder. The MSA patients and controls will receive CSF and blood sampling at one study visit.

• MSA patients

  o Inclusion criteria: Patients suffering from "probable" MSA according to clinical consensus criteria (Gilman et al, 2008), Age >30 Written informed consent Patient covered by the national health system

  o exclusion criteria: UMSARS IV score > 4 points Patient under tutelage Patient unable to give consent Patients receiving anticoagulants, showing abnormal coagulation on blood testing or thrombocytopenia are excluded from this study

• Controls (patients requiring spinal tap without suffering from a neurodegenerative disorder) o Inclusion criteria: Patients not suffering from a neurodegenerative disorder and requiring a spinal tap Age >30 Written informed consent Patient covered by the national health system o exclusion criteria: Similar to MSA patients

Cases will be selected from cohort of 90 MSA patients referenced in Bordeaux University Hospital.

Controls will be selected from patients requiring spinal tap without being affected by a neurodegenerative disorder and paired in age and gender with cases.