reza boostani neurology department, ghaem hospital, mashhad university of medical sciences, mashhad, ir iran ali mellat neurology department, shahid sadoughi hospital, yazd university of medical sciences, yazd, ir iran; shahid sadoughi hospital, yazd university of medical sciences, yazd, ir iran. tel/fax: +98-3518224001 reza afshari medical toxicology research centre, mashhad university of medical sciences, mashhad, ir iran siavash derakhshan neurology department, north khorasan university of medical sciences, bojnourd, ir iran morteza saeedi neurology department, ghaem hospital, mashhad university of medical sciences, mashhad, ir iran ehsan rafeemanesh occupational and environmental health department, mashhad university of medical sciences, mashhad, ir iran

D Agrawal R Vohra P P Gupta S Sood