A 39-year-old man complains of severe daily headaches that he describes as throbbing and "burning," with a sensation
of pressure. He rates the severity of his pain as 8 to 10 on a 10-point visual analog scale (VAS) in which 10 is
the most severe. The mean duration of the headaches is 12 hours, and the mean frequency is 5 days per week. Between
the episodes of severe headache, he has constant "minor" headaches that are not as severe (mean severity, 3 to 5 on a
10-point VAS). Within the past 5 months, he has never been totally free of headache.