1. Digestive Diseases Research Center, Digestive Diseases Research Institute, Tehran University of Medical Sciences , Tehran , Iran
2. Neurology Department, Qazvin University of Medical Sciences , Qazvin , Iran
3. Department of Neurology, University of Pennsylvania , Philadelphia, PA , USA
4. Department of Neurology, Vagelos College of Physicians and Surgeons, and Department of Epidemiology, Mailman School of Public Health, Columbia University , New York, NY , USA
5. Division of Gastroenterology, Massachusetts General Hospital and Harvard Medical School , Boston, MA , USA
6. Inflammatory Bowel Disease Center, University of Chicago Medicine , Chicago, IL , USA