Spastic paraparesis is one of the most disabling functional deficits in the population with multiple sclerosis between 18 and 80 years of age and at any functional level. Infiltration with Botulinum Toxin is a clinical practice that has been carried out for years with clinical evidence of improvement in the patient's walking patterns and quality of life. We assume that the infiltration of this product can generate a direct benefit in the walking ability of these patients and secondarily improve their quality of life.

Inclusion Criteria:

• Acceptance and signature of informed consent.
• Age between 18 and 80 years old, both included.
• Patients with relapsing remitting multiple sclerosis (RRMS), progressive secondary (SP) and primary progressive (PP), with spasticity resistant to usual treatment, either because of the severity of the spasticity or because of intolerance to side effects.
• Outpatients with spastic paraparesis that causes gait deficiency.
• Patients with an EDSS score between 2 and 6, both included.
• Patients with segmental involvement in MAS >1 in two or more muscle groups in the lower extremities.
• Absence of cognitive disability. Score less than 5 on the SPMSQ scale of Pfeiffer.
• Possibility of carrying out the treatment (method of administration, scheduled visits) and scales correctly.
• Women of childbearing potential should use an effective contraceptive method (hormonal contraceptives, intrauterine device, condom) or refrain from having sex in order not to get pregnant. A woman is considered to be fertile after menarche and to become postmenopausal, unless she has undergone a permanent sterilization procedure (hysterectomy, salpingectomy, bilateral oophorectomy). A postmenopausal state is defined as absence of menstruation for 12 months without an alternative medical cause.

Exclusion Criteria:

• Psychiatric illness that hinders participation in the trial.
• Comorbidity that threatens the patient's life in the short term (severe liver disease, cardiovascular disease, etc.).
• Osteoarticular disorder that prevents physical activity.
• Pregnancy or lactation.
• Lack of primary or secondary response to any type of Botulinum Toxin for the treatment of MS previously detected.
• Sensitivity to Botulinum Toxin or to any excipient.
• Any medical condition that, in the opinion of the investigator, may compromise compliance with the objectives and / or procedures of this protocol or preclude the administration of Botulinum Toxin.
• Changes in the treatment regimen of any drug that directly or indirectly interferes with neuromuscular function within 4 weeks before the start of the study treatment.