I understand that they did not consider neck trauma in the study. But anyway they find a slight correlation.
Physical trauma and risk of multiple sclerosis: A systematic review and meta-analysis of observational studieshttp://www.ncbi.nlm.nih.gov/pubmed/24246497
The result of the meta-analyses of high quality case-control studies suggests a statistically significant association between premorbid head trauma and the risk for developing MS. However, cohort studies did not. Future prospective studies that define trauma based on validated instruments, and include frequency of traumas per study participant, are needed.