TM is a rare neurological disorder, one of a group of "neuroimmunologic" diseases of the central nervous system, which also include ADEM, NMO (Devic's Disease) and MS. These conditions all involve inflammatory attacks in the central nervous system. They are differentiated primarily by the location of the attack, and by the attacks being either monophasic (one off) or multiple episodes. These disorders share common mechanisms and have many common symptoms.