There are four main types of multiple sclerosis: relapsing-remitting MS, primary-progressive MS, secondary-progressive MS, and progressive-relapsing MS. Relapsing-remitting MS involves clearly defined attacks followed by periods of remission with no progression. Primary-progressive MS results in steady worsening from the start with no distinct attacks. Secondary-progressive MS follows an initial period of relapsing-remitting MS with steady worsening. Progressive-relapsing MS involves steady worsening with superimposed attacks. Diagnosis is based on neurological history, exam, and tests like MRI and spinal tap.