Final answer:
Unilateral, severe periorbital headache is commonly associated with cluster headaches and may present with tearing and conjunctival erythema.
Step-by-step explanation:
Unilateral, severe periorbital headache is commonly associated with cluster headaches. The symptoms may include tearing, conjunctival erythema, nasal congestion, and rhinorrhea. However, blurred vision, photophobia, dizziness, and vertigo are not typically associated with this type of headache.
Cluster headaches are a type of primary headache disorder characterized by recurrent, severe headaches that occur in clusters or groups. They are considered one of the most painful types of headaches and are often described as excruciating or burning in nature. Cluster headaches typically occur in cyclical patterns, with periods of intense headache attacks followed by headache-free intervals.