45-year-old man presents with a daily headache. He describes two attacks per day over the past 3 weeks. Each attack lasts about an hour and awakens the patient from sleep. The patient has noted associated tearing and reddening of his right eye as well as nasal stuffiness. The pain is deep, excruciating, and limited to the right side of the head. The neurologic examination is nonfocal. The most likely diagnosis of this patient’s headache is

**Core Concept**
The patient's presentation suggests a primary headache disorder characterized by recurrent, unilateral, and severe headaches with autonomic symptoms, specifically tearing and nasal stuffiness.

**Why the Correct Answer is Right**
The patient's symptoms are classic for cluster headaches, a type of primary headache disorder. Cluster headaches are typically characterized by severe, unilateral orbital, supraorbital, or temporal pain lasting 15-180 minutes, often accompanied by autonomic symptoms such as lacrimation, conjunctival injection, nasal congestion, or rhinorrhea. The pain is usually deep and excruciating, and the patient is often awakened from sleep by an attack. The nonfocal neurologic examination helps to rule out secondary causes of headache.

**Why Each Wrong Option is Incorrect**
**Option A:** Migraine headaches typically present with unilateral or bilateral pain, often accompanied by photophobia, phonophobia, and nausea. However, cluster headaches are distinct due to their shorter duration, deeper location, and autonomic symptoms.
**Option B:** Tension headaches are characterized by bilateral, band-like pain, often described as a dull ache or pressure. The patient's severe, unilateral pain and autonomic symptoms are not consistent with tension headaches.
**Option C:** sinusitis may present with headaches, but the patient's symptoms of tearing, reddening of the eye, and nasal stuffiness are more typical of autonomic symptoms associated with cluster headaches.

**Clinical Pearl / High-Yield Fact**
Cluster headaches are often referred to as "suicide headaches" due to their intense pain, which may drive patients to seek relief through dangerous means. This highlights the importance of accurate diagnosis and effective treatment of these headaches.

**Correct Answer: C. Cluster headache.**

✓ Correct Answer: B. cluster headache