We report here 39 cases in which definite multiple sclerosis (MS) was precipitated or exacerbated by specific hyperextension–hyperflexion cervical cord trauma. The worsening or onset of the symptomatic disease bore a striking temporal relationship to the focal injury. Our data suggests that central nervous system (CNS)-specific acute physical trauma such as cervical cord hyperextension–hyperflexion injury may aggravate latent clinical symptoms in MS. The deterioration of MS bore no direct relationship with the severity of neck injury. Possible pathogenic mechanisms of focal CNS-specific trauma aggravating the course of asymptomatic or benign MS are discussed. This may have implications in improving our understanding of the factors that may modify the clinical course of MS.