**1. Introduction**

According to the definition made by the International Organization for Research on Aging (IASP), pain is a sensorial, emotional, unpleasant sensation about someone's past experiences, whether they are connected to an organic gown or not, starting from anywhere in the body.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
