Other disorders that present with headache along with systemic symptoms and signs include metastatic and primary malignant tumors involving the brain, meninges, and skull, and a variety of infections and other inflammatory diseases. Neoplasms that may elevate the erythrocyte sedimentation rate and cause both local and systemic symptoms are prevalent in the older age group, which is also selectively susceptible to developing temporal arteritis, so the differential diagnosis may be somewhat difficult on clinical grounds alone. MRI and CT should rule out tumors that confound the clinical diagnosis. On occasion, however, lumbar puncture and CSF examination may be needed to rule out inflammatory (granulomatous), infectious, and neoplastic meningeal infiltrative diseases. Rarely, paranasal sinus infection might mimic both the local and systemic symptoms of temporal arteritis, but this will be identified by cranial imaging studies. The symptoms of polymyalgia rheumatica were refractory to standard treatment in a 59-year-old woman but were promptly relieved by removal of a large hepatic cavernous hemangioma (Kadry et al 2000). The mechanism by which this lesion caused the symptoms in this case is unclear.
On the other hand, temporal arteritis may mimic other diseases and be missed as the underlying cause. Ascending aortic aneurysm has been shown histologically to be caused by underlying temporal arteritis (Hamano et al 1999). Myocardial infarction can complicate known temporal arteritis or may rarely be the presenting feature of the disease (Freddo et al 1999). Temporal arteritis presenting as subclavian artery stenosis has also been described (Sato et al 1993). Cases of temporal arteritis presenting as orbital inflammatory pseudotumor (de Heide and Talsma 1999) and panuveitis (Rajesh and Cole 2000) have been recorded as well. Temporal arteritis was found to be the most frequent specific multisystem disease in an elderly population presenting as fever of unknown origin (Tal et al 2002). A case of giant cell arteritis involving the ovaries and adjacent tissues in a 75-year-old woman who was asymptomatic for the disease was discovered during surgery to remove an ovarian cyst. Temporal artery biopsy subsequently demonstrated active temporal arteritis in the woman (Onuma et al 2007).
In 1990 Hunder and colleagues published The American College of Rheumatology 1990 criteria for the classification of giant cell arteritis (Hunder et al 1990). To qualify for diagnosis patients must meet 3 of the following 5 criteria: (1) age over 50 years, (2) new onset of localized headache, (3) temporal artery tenderness or decreased temporal artery pulse, (4) erythrocyte sedimentation rate greater than or equal to 50 mm/hour, or (5) positive temporal artery biopsy. Murchison and colleagues performed a study to determine if the American College of Rheumatology classification criteria can accurately establish the diagnosis of giant cell arteritis without performing temporal artery biopsy. The study cohort consisted of 112 patients who underwent adequate (minimum 2 cm) temporal artery biopsy prior to, or no more than 5 days after, starting corticosteroid treatment. All patients also had ischemic visual loss involving 1 or both eyes (central retinal artery occlusion or anterior ischemic optic neuropathy). They found that 9 of 35 patients with positive biopsy would not have been diagnosed as having giant cell arteritis using the criteria alone and another 16 patients met only 2 of the criteria and would have needed the biopsy to diagnose giant cell arteritis. In addition, 11 of 39 patients with negative biopsies met the criteria for diagnosis, which could mean only that temporal artery biopsy may be false negative in the presence of active giant cell arteritis. The authors conclude that data indicate that temporal artery biopsy is indicated in all patients suspected of having giant cell arteritis (Murchison et al 2012).