Which type of headache can help in diagnosing an ipsilateral Horner's syndrome?

Cluster headaches are uniquely associated with autonomic symptoms on the same side as the headache, including Horner's syndrome. This condition occurs due to disruption of the sympathetic pathways, often caused by a lesion in the carotid artery region or a neighboring structure.

In the case of cluster headaches, patients may exhibit ipsilateral signs such as ptosis (drooping of the eyelid), miosis (constricted pupil), and anhidrosis (lack of sweating) along with severe unilateral pain around the eye, making it an important clinical scenario to consider when diagnosing ipsilateral Horner's syndrome.

Migraine headaches can also present with unilateral symptoms but are less specifically associated with Horner's syndrome. Tension headaches typically do not present with autonomic features at all and are often bilateral in nature. Brain tumor headaches can have various presentations depending on the location but are not specific to Horner's syndrome as cluster headaches are. Thus, cluster headaches are the key headache type that can provide insight into the presence of ipsilateral Horner's syndrome.