A focus on secondary progressive multiple sclerosis (SPMS): challenges in diagnosis and definition.

Secondary progressive multiple sclerosis (SPMS) is the second most common form of multiple sclerosis (MS). One in two relapse remitting multiple sclerosis (RRMS) patients will develop SPMS within 15 years and up to two-thirds after 30 years, leading to a progressive decrease of neurological function and limitation of daily activities. Nevertheless, the SPMS diagnosis is often established retrospectively and delayed up to 3 years due to several patient- and clinician-related factors. Definitive clinical diagnostic criteria are lacking and research is currently ongoing to identify imaging and biochemical biomarkers. As new therapies are introduced, early SPMS diagnosis may represent a window of opportunity for intervention. New approaches, endpoints or technologies could help physicians establishing a diagnosis. Here, we review SPMS in relation to its diagnostic and definition challenges and current screening techniques and tools.