Which finding is associated with Horner's syndrome in cluster headaches?

• A. Ptosis, miosis, and anhidrosis
• B. Ptosis and mydriasis
• C. Conjunctival injection only
• D. Eyelid edema with facial swelling

Answer: (A)

Horner's syndrome comes from disruption of the oculosympathetic pathway to the eye, so you see signs from sympathetic loss rather than excess. The key finding is the triad of ptosis (due to loss of Müller's muscle support), miosis (pupil constriction from reduced sympathetic dilation), and anhidrosis on the same side of the face. In cluster headaches, this sympathetic involvement can accompany the autonomic features of the attack, making that combination the telltale sign.

Other options don’t fit because ptosis with mydriasis would mean the pupil is enlarged, which is not Horner’s pattern (Horner’s causes constricted pupils). Conjunctival injection alone doesn’t include the pupil or eyelid changes of Horner’s, and eyelid edema with facial swelling can occur in cluster attacks for other reasons but is not the Horner’s syndrome triad.