Which condition is most likely causing scalp tenderness and loss of vision in a 50-year-old male?

The condition most likely causing scalp tenderness and loss of vision in a 50-year-old male is giant cell arteritis. This is an inflammatory disease that affects the large and medium-sized blood vessels, particularly the temporal arteries, which run along the side of the head. Patients often experience symptoms such as scalp tenderness or pain when brushing their hair, as well as vision changes, which can include blurry vision, sudden vision loss, or even permanent vision impairment if untreated.

In individuals over 50, the risk for giant cell arteritis increases, making it a critical consideration when a patient presents with the accompanying symptoms. Additionally, this condition can lead to serious complications, such as permanent blindness, if not diagnosed and treated promptly.

The other options generally do not present with both scalp tenderness and loss of vision. Cluster headaches are characterized by severe, unilateral pain but do not typically involve scalp tenderness or significant vision loss. Migraines, whether with aura or without, can cause a variety of neurological symptoms, but loss of vision and scalp tenderness are not the primary features associated with these conditions.