Certain types of diseases and conditions may diminish and intensify in severity over
time. For example, symptoms of multiple sclerosis vary from person to person and may
change over time in the same person. Some symptoms will come and go over the course
of the disease, while others may be more permanent. Determining onset in these cases
can be difficult because of the variation in severity. When determining onset, the
adjudicator considers the history of the disease process, the length of the exacerbations
and remissions and the severity of the signs and symptoms, in conjunction with medical
evidence, vocational history, and other evidence about the severity of the impairment.