A 75 years old man with an unremarkable past medical history presents with a complaint of new headache for the past 2 weeks. He notes that the headache is localized over the left temple and he has noticed associate jaw pain and chewing discomfort. His medical history is unremarkable with the exception of occasional complaints of pain and stiffness in the shoulders and hips, which are worse in the morning but progressively improved throughout the day. Laboratory evaluation demonstrates evidence of inflammation, including an elevated ESR, C-reactive protein, and platelets. What is the most likely diagnosis?