Efficacy of L-threo DOPS on Orthostatic Hypotension Symptoms and Other Non-motor Symptoms in Patients With MSA

Inclusion Criteria: * MSA patients (possible or probable, MSA-P or C (according to revised criteria, Gilman et al 2008)). * Aged 30 to 80 years, * Able to walk at least 10 meters * With symptomatic OH (score of at least 3 at one of the items of Part I of the OH scale (OHQ)) * Documented fall in systolic blood pressure of at least 20 mmHg, and/or in diastolic blood pressure of at least 10 mmHg, within 3 minutes after standing. * Able to fill in the evaluation questionnaires with or without help * With no significant problems with swallowing. * Stable anti-parkinsonian, dysautonomia and depression treatments for the 4 weeks before the study and during the entire study * Signed written informed consent for the present study. Exclusion Criteria: * Dementia (DSM-IV, Mini-Mental State Examination (MMSE) \< 24/30) * Concomitant use of vaso-constrictive drugs, other than midodrine. Patients taking vasoconstrictor agents such as ephedrine, dihydroergotamine, must stop taking these drugs at least 2 days or 7 half-lives prior to their baseline visit (Visit 1); the association with midodrine may be kept at a stable dose not exceeding 3 tablets (7.5 mg) / day if the patient has no CV history. This will be discussed case by case with the coordinating center and the safety committee of this study. * Taking anti-hypertensive medication