Inclusion Criteria:  Signed Informed Consent Form Age 18-65 years at time of signing Informed Consent Form Able and willing to provide written informed consent and to comply with the program protocol according to ICH and local regulations Ability to comply with the study protocol, in the investigator's judgment Adequately recovered from any acute illness at the time of screening, and considered clinically well enough to participate, in the opinion of the treating physician Patients with retinopathy of prematurity should have evidence of stable disease Genetic confirmation of 5q SMA documented on standard genetic tests for the disorder Received nusinersen treatment for ten months or more Presence of 10% compound muscle action potential (CMAP) amplitude decrement on 3 Hz repetitive nerve stimulation of the spinal accessory or ulnar nerve  Negative blood pregnancy test at screening (all women of childbearing potential, including those who have had a tubal ligation), and agreement to comply with measures to prevent pregnancy and restrictions on sperm donation, as below:  For women who are not prematurely menopausal (≤12 months of non-therapy induced amenorrhea) or surgically sterile (absence of ovaries and/or uterus):agreement to remain abstinent (refrain from heterosexual intercourse) or to use two adequate methods of contraception, including at least one method with a failure rate of < 1% per year, during the treatment period and for at least 28 days after the last dose of study drug. The reliability of sexual abstinence needs to be evaluated in relation to the duration of the clinical trial and the preferred and usual lifestyle of the patient. Periodic abstinence (e.g., calendar,ovulation, symptothermal, or post-ovulation methods) and withdrawal are not acceptable methods of contraception. Barrier methods must always be supplemented with the use of a spermicide. Examples of contraceptive methods with a failure rate of < 1% per year include bilateral tubal ligation, male sterilization, established and proper use of hormonal contraceptives that inhibit ovulation, hormone-releasing intrauterine devices, and copper intrauterine devices.  Exclusion Criteria:  Pregnant or breastfeeding, or intending to become pregnant during the study or within 30 days after the final dose of Risdiplam Women of childbearing potential must have a negative serum pregnancy test result within 14 days prior to initiation of study drug. Treatment with an investigational therapy within 180 days prior to initiation of study drug History of established diagnosis of neuromuscular junction disorder Co-morbid conditions that preclude travel, testing, or study medications Patients who are, in the investigator's opinion, mentally or legally incapacitated to provide an informed consent