American Board of Internal Medicine (ABIM) Certification Practice Exam

What condition should be suspected in a patient with acute headache and Horner syndrome?

1. Intracranial hemorrhage

2. Carotid artery dissection

3. Subarachnoid hemorrhage

4. Brain tumor

The correct answer is: Carotid artery dissection

In a patient presenting with an acute headache accompanied by Horner syndrome, carotid artery dissection is the condition that should be strongly suspected. Horner syndrome is characterized by the triad of ptosis (drooping of the eyelid), miosis (constricted pupil), and anhidrosis (lack of sweating) on the affected side of the face. This syndrome results from disruption of sympathetic nerve fibers, which can occur due to various causes, including carotid artery dissection. Carotid artery dissection can lead to ischemia and pain, often resulting in sudden and severe headache. The dissection can compromise the blood flow to the brain, leading to neurological manifestations, including Horner syndrome due to injury to the sympathetic chain that runs alongside the carotid artery. This condition typically presents with a unilateral headache that can be accompanied by neck pain, transient ischemic attack symptoms, or even stroke in advanced cases. In comparison, while intracranial hemorrhage, subarachnoid hemorrhage, and brain tumors can cause headaches and other neurological deficits, they do not specifically cause Horner syndrome as a direct result. Therefore, the specific association between acute headache and Horner syndrome makes carotid artery dissection the most likely diagnosis in this case