The recent article by de Seze et al1 correctly identifies a set of clinical signs and symptoms that may be useful in differentiating acute disseminated encephalomyelitis (DEM) from the first episode of multiple sclerosis (MS). However, their contention that DEM may evolve or convert to MS implies that the 2 conditions are, if not identical, at least closely related. In fact, they differ in at least 2 ways. Multiple sclerosis occurs in people who are genetically vulnerable, a feature noticeably lacking in DEM. Even more importantly, ever since Robert Carswell and Jean Cruveilhier published their classic illustrations of MS almost 200 years ago, the sharp edges of the typical MS lesion—so aptly described by Ludo van Bogaert as découpées à l’emporte-pièce—have been recognized by neuropathologists of the caliber of Ivan Bertrand, Jean Gruner, and François Lhermitte, to name just a few, as pathognomonic for MS; they are never seen in DEM. It is difficult to accept the concept that DEM would morph into a genetically and pathologically dissimilar disease.
Poser CM. Multiple Sclerosis and Recurrent Disseminated Encephalomyelitis Are Different Diseases. Arch Neurol. 2008;65(5):672-677. doi:10.1001/archneur.65.5.674-a