Patients with severe multiple sclerosis (MS) were increasingly receiving autologous hematopoietic stem cell transplantation (aHSCT). For a study, the researchers sought to look at the short and long-term results after aHSCT in the Ottawa cohort to find its effectiveness in disease remission and safety. From October 2001 to February 2021, researchers looked at the results of all patients who had aHSCT for MS at the center and were followed for at least 6 months. Busulfan+cyclophosphamide was employed as a conditioning regimen for aHSCT, followed by anti-thymocyte globulin (ATG) post-transplantation of a CD34+ chosen graft. The number of new clinical relapses following the transplant was the primary outcome. The new MRI lesions, overall survival, and safety were the secondary endpoints. Researchers also determined the association between baseline Expanded Disability Status Scale (EDSS) scores and how they changed over time. Up till February 2021, a total of 72 individuals with aggressive MS received aHSCT. The majority of the patients (n=62) had relapsing-remitting MS, while 8 had secondary progressive (SP) MS and 2 had primary progressive (PP) MS. The time between follow-ups ranged from 8 months to 20 years. There was not a single new relapse during the entire follow-up period. There were 206 relapses pre-transplant, based on 195.9 patient-years of follow-up (1.1 relapses/patient/year). With 288 patient-years of follow-up after the transplant, there were no relapses. Furthermore, no further disease-modifying treatment (DMT) was given to any of the patients. As per data, one person died 27 days after undergoing aHSCT due to sepsis and liver veno-occlusive disease (at a time when busulfan was being given orally). Another patient died of pneumonia 67 months after undergoing aHSCT during the follow-up period. MRI scans were done on an as-needed basis during the follow-up, but no new lesions have been discovered since the transplant. On 52 of 72 patients, the EDSS long-term scores were available. When patients had a lower EDSS at baseline, EDSS decreases (improvements) were more common post-transplant. Only 6/26 individuals with a baseline EDSS more than or equal to 5 improved their EDSS scores, compared to 13 patients with a baseline EDSS less than 5. The study confirms aHSCT’s long-term efficacy and safety in the treatment of aggressive MS. Patient selection was critical, with higher outcomes reported in patients who have experienced minor handicaps at the aHSCT. While there were some dangers, including mortality, overall morbidity and mortality were low (2.8%) and comparable to other research. There was also a long-term monetary and safety benefit to not having to take DMT daily. More detailed information will be supplied.