Ibn Sina, known as Avicenna in the West, was a celebrated Persian thinker, philosopher, and physician who is remembered for his masterpiece, The Canon of Medicine. The Canon that served as an essential medical encyclopedia for scholars in the Islamic territories and Europe for almost a millennium consisted of 5 books. In the third book, Avicenna described patients with symptoms of carotid hypersensitivity syndrome. These patients, who had excessive yawning, fatigue, and flushing, dropped following pressure on their carotids. Based on such history, it seems that Avicenna was the first to note the carotid sinus hypersensitivity, which presents with vasovagal syncope following compression of the carotid artery. In this paper, we presented a brief account of Avicenna's life and works and discuss his description of the so-called carotid hypersensitivity syncope. Notwithstanding his loyalty to the Greek theory of humoralism, Avicenna set forth his own version of "theory of spirits" to explain the mechanism of this disease. An account of the theory of spirits is also given.