 According to some pathologists, a pathological definition is required because clinical definitions have problems with differential diagnosis and they always use a pathological definition on articles about post-mortem retrospective diagnosis, but for practitioners that need a diagnosis as soon as possible MS is often regarded as a pure clinical entity, defined simply by a positive result in the standard clinical case definition being then named "clinically definite MS" (CDMS, Poser) or simply "MS" (McDonald).Both definitions lead to different results.For example, confluent subpial cortical lesions are the most specific finding for MS, being exclusively present in MS patients.