1. Department of Medicine, Faculty of Medicine, Kuwait University, Kuwait City P.O. Box 24923, Kuwait
2. Neurology Unit, Department of Medicine, Mubarak al Kabeer Hospital, Ministry of Health, Jabriya 13001, Kuwait
3. Department of Population Medicine, Qatar University, Doha P.O. Box 2713, Qatar
4. Department of Medical Sciences, Frank Netter School of Medicine, Quinnipiac University, Hamden, CT 06518, USA