Cluster headaches are defined as a group of at least five headache attacks causing unilateral orbital, supraorbital and/or temporal pain, with at least one of the following simultaneous associated findings on the affected side:

1. conjunctival injection
2. lacrimation
3. nasal congestion
4. rhinorrhea
5. ptosis
6. miosis
7. sweating on the forehead

Cluster headaches can occur at a frequency of one every other day t  eight episodes per day.

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