Overview. Clinical types of MS. MS is a chronic recurrent inflammatory disorder of the CNS. The disease results in injury to the myelin sheaths, the oligodendrocytes, and, to a lesser extent, the axons and nerve cells themselves. 1-5 The symptoms of MS vary, depending in part on the location of plaques within the CNS. Common symptoms include sensory disturbances in the limbs, optic nerve dysfunction, pyramidal tract dysfunction, bladder or bowel dysfunction, sexual dysfunction, ataxia, and diplopia. 5 Four different clinical courses of MS have been defined. 6 The first, relapsing–remitting MS (RRMS), is characterized by self-limited attacks of neurologic dysfunction. These attacks develop acutely, evolving over days to weeks. Over the next several weeks to months, most patients experience a recovery of function that is often (but not always) complete. Between attacks the patient is neurologically and symptomatically stable. The second clinical course, secondary progressive MS (SPMS), begins as RRMS, but at some point the attack rate is reduced and the course becomes characterized by a steady deterioration in function unrelated to acute attacks. The third clinical type, primary progressive MS (PPMS), is characterized by a steady decline in function from the beginning without acute attacks. The fourth type, progressive–relapsing MS (PRMS), also begins with a progressive course although these patients also experience occasional attacks.