Also known as synesthesialgia, synaesthesia algica, and synesthesia algica. All four terms stem from the Greek words sun (together, unified), aisthanesthai (to notice, to perceive), and algos (pain). They refer to a painful sensation which gives rise to a secondary painful sensation that has no objectifiable substratum. Whether the secondary painful sensation should be conceptualized as a type of * hallucinated pain or rather as a type of referred pain may not always be clear. The term synaesthesialgia is also used to denote a condition in which a stimulus produces pain on the affected side of the body, but a pleasant one -or none at all - on the healthy side. A third meaning is 'painful synaesthesia'. In the latter case, the term refers to a painful sensation which may be triggered by a sudden sound or light stimulus.
References
Stedman's Medical Dictionary Staff, ed. (2005). Stedmans medical dictionary, 28th edition. Philadelphia, PA: Lippincott, Williams and Wilkins.
Dictionary of Hallucinations. J.D. Blom. 2010.