The absence of attacks with new neurologic symptoms, or recurrence of older problems, does not necessarily mean that a person has progressive MS. Patients can be stable for long periods of time. To recognize progression in MS, neurologic difficulties must be progressing. A neurologist can only determine this if the patient has progressed or changed neurologically.
The patient must undergo a complete quantitative neurologic examination to determine and then record dis-ability scores for comparison with previous and future examinations. It takes special training to perform such examinations with consistency and to provide usable information. However, the patient with progressive disease can point out to the neurologist what types of problems are progressing.
Reasons why primary progressive patients do not ordinarily have attacks are unknown. Actually, about one third of the patients who originally experience only progressive problems subsequently do experience one or more exacerbations, but when they do, they have relatively few.
It is possible that those who never have acute attacks have a different type of disease process that involves antibody-mediated demyelination independent of lymphocytes. At the present, this is purely speculative.
In addition to those patients with primary progressive MS, many patients with secondary progressive illness stop having clear-cut attacks and progress in a waxing-and-waning fashion. After a dozen years of illness, progression and attacks may no longer be evident to the patient and physician alike.
Evidence of progression by examination may be difficult to detect in many patients. Longer term observation of these patients may reveal continued worsening; that is, neurologic functions that appear to be preserved may actually be partially lost.