Safety and Efficacy Study of Pyridostigmine on Patients With Spinal Muscular Atrophy Type 3

Inclusion Criteria: * Spinal muscular atrophy type 3, genetically confirmed * Age higher than 6 years old * Ambulatory patient * Informed consent signed * More than 100 meters of walking at 6-minute walk test at screening * Value at screening and baseline in a range of 20% of the highest value at 6-minute walk test Exclusion Criteria: * Patient who had surgical intervention or suffer from a recent traumatism (less than 6 months) * Associated pathology such as endocrinopathy, infectious disease, allergy, myopathy, chronic or acute inflammatory pathology, during 3 weeks preceding the inclusion. * Other therapeutics than food supplements or those frequently prescribed in spinal muscular atrophy or its complications * Non tolerance of electromyography * Limited collaboration due to trouble in information comprehension * Pathology inducing contra-indication for pyridostigmine treatment (allergy at molecule, asthma, Parkinson disease, mechanic obstruction of urinary or digestive tracts)