1. Department of Anatomy; Tokyo Dental College; 2-9-18 Misaki-cho, Chiyoda-ku Tokyo, 101-0061 Japan
2. Department of Neurology, Wonkwang University School of Medicine and Hospital; Institute of Wonkwang Medical Science, 895; Muwang-ro, Iksan Jeonbuk, 570-711 Korea
3. Division of Internal Medicine; Iwamizawa Asuka Hospital; 297-13 Shibun-cho Iwamizawa, 068-0833 Japan
4. Department of Anatomy and Human Embryology, Institute of Embryology, Faculty of Medicine; Complutense University; Madrid 28040 Spain