The patient most likely has had a carotid artery dissection. Despite his migraine history, the report of a different type of headache should raise suspicion of a secondary headache. Cervicocephalic dissection is an uncommon but important cause of stroke, especially in persons younger than 50 years. The presence of ipsilateral neck pain and ischemic complications, such as transient monocular visual loss and Horner syndrome (miosis, ptosis, and anhidrosis), is characteristic of carotid artery dissection and may not be associated with preceding trauma. The cause of an associated stroke is primarily thrombus formation at the site of dissection with subsequent artery-to-artery embolism. The imaging modality of choice is an MRI of the soft tissues in the neck, which will demonstrate a crescent-shaped hematoma within the internal carotid artery wall on T1-weighted images. Aspirin is considered the treatment of choice to prevent ongoing ischemic complications or stroke.

Cluster headache is a primary headache disorder classified as a trigeminal autonomic cephalalgia. This type of headache presents with unilateral head pain, which is typically periorbital or temporal (“trigeminal”) but sometimes may affect the face or neck. Cranial autonomic features, such as ptosis, miosis, tearing, and nasal congestion, are characteristic. Cluster headaches appear in a repetitive fashion, one to eight times daily, and are brief, with durations between 15 minutes and 3 hours. Related trigeminal autonomic cephalgias, such as chronic paroxysmal hemicrania or short-lasting unilateral neuralgiform headaches with conjunctival injection and tearing (SUNCT syndrome), occur with greater frequency and are of shorter duration, lasting minutes and seconds respectively. In this patient, the headache developed abruptly and has lasted an entire day, with no prior pattern indicative of these disorders.

The patient has a history of migraine, but his description of a “different” headache should raise concerns for secondary explanations. The duration of the attack is not outside the acceptable range for migraine (4 to 72 hours), and migraine can present with either unilateral or bilateral discomfort. Visual aura is described by 25% to 35% of those with established migraine, but monocular visual loss is much more uncommon than binocular hemifield impairment. Ptosis and miosis resulting from migraine are quite uncommon. Red flags in this patient's case include the “different” nature of the headache, the new symptoms of neck pain and monocular visual dysfunction, the abrupt onset of pain during physical exertion, and (most importantly) the abnormal physical examination findings. This combination renders migraine unlikely.

Vertebral artery dissection can present with acute head or neck pain associated with physical exertion or trauma but also can occur spontaneously. The most common symptom is headache, but neurologic symptoms or deficits also occur. As many as 25% of ischemic strokes in younger patients result from either carotid or vertebral artery dissection. Because the vertebrobasilar supply of the occipital cortex or cerebellum may be affected, symptoms of loss of vision or balance are common. Although ptosis and miosis may arise from infarction of the lateral medulla (Wallenberg syndrome) in vertebral dissection, they are always accompanied by other findings, such as vertigo, dysarthria, dysphagia, ataxia, and loss of pain and temperature sensation ipsilaterally in the face and contralaterally in the body.