It is established that the repetition of the sessions of cortical stimulation over a week improves their analgesic efficacy. However, this effect does not exceed a few weeks and is much lower than that of the stimulation implanted surgically. Implanted stimulation operates periodically, several times a day, and this "repetition of doses ", akin to the regular taking of a medicine, may explain its longer efficacy for pain relief which, may extend over several years (André-Obadia and al 2014).