C5b. Disability Scale: A descriptive categorical scale will be used to characterize the subject's headache-related disability. On this scale, subjects describe their disability as "1) none; 2) mildly impaired (having a little bit of difficulty doing what I usually do); 3) moderately impaired (having a great deal of difficulty doing what I usually do and can only do very minor activities); or 4) severely impaired (requiring bed rest)" [25].