what percentage of patients show a decline in headaches after
On average, a cluster. period lasts 6 to 12 weeks while remissions can last up to 12 months or longer. The episodic form is the most common, affecting 80 to 90 percent of patients with cluster. headache. It is characterized by periods of attacks (clusters or bouts) and periods of remission. In a bout, patients may experience one to eight attacks per day, and bouts may last from. seven days to 12 months [1].