Is it time to revise the classification of geographical distribution of multiple sclerosis?

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS). Although the precise mechanisms involved in MS pathology have remained unclear, it is generally thought to be an autoimmune disease that targets myelin in the CNS. It afflicts more than one million persons worldwide.1 MS is the leading cause of disability in young and middle-aged people and adversely affects employment, social relationships and quality of life. It is also one of the best studied and epidemiologically well-defined neurological diseases.