ahmad zeinali neurology department, shahid sadoughi hospital, yazd university of medical science, yazd, ir iran abolghasem rahimdel neurology department, shahid sadoughi hospital, yazd university of medical science, yazd, ir iran reza boostani neurology department, qaem hospital, mashhad university of medical science, mashhad, iriran ali mellat neurology department, shahid sadoughi hospital, yazd university of medical science, yazd, ir iran; shahid sadoughi educational and research center, yazd, ir iran. tel: +98-3518224001, fax: +98-3518224100