Important Rare Neuroimmunological Diseases

Abstract

All of the following syndromes are rare and have annual incidences of less than 1/1,000,000, but have importance over and above their frequency in the population. These disorders are sometimes classified as “zebras,” disorders so unusual that they are normally only considered long down the list of likely suspects. As noted in Chap. 6, in the section on unusual mimics of multiple sclerosis, the term zebra has its origin in the phrase: “When you hear hoofbeats, think horses, not zebras,” i.e., when evaluating a patient with an unknown diagnosis, a physician should remember that common diseases occur commonly and that it is more likely to get an unusual manifestation of a common disease than to have a common presentation of a zebra. However, all neuroimmunologists have to think of zebras occasionally when the diagnostic situation does not bring to mind any “horses.” The conditions described below constitute far from an exhaustive list. I encourage neurologists who read this chapter to contact me (pachner@umdnj.edu) to describe their most memorable zebra. These syndromes have been divided into three different categories: infectious/postinfectious, autoimmune, and idiopathic, and provided a short description. At the end of each disease description is a short section on why the disease is important out of proportion to its incidence.