Temporal arteritis, also called giant cell arteritis (GCA), is diagnosed through a combination of blood tests, imaging, and often a biopsy of the temporal artery. Because the condition can cause permanent vision loss if untreated, doctors typically start steroid treatment immediately on suspicion and confirm the diagnosis afterward. The condition occurs almost exclusively in people over age 50, and that age threshold is a baseline requirement for diagnosis.
Symptoms That Raise Suspicion
The earliest symptoms often feel like the flu: fatigue, loss of appetite, and low-grade fever. These vague signs are easy to dismiss, which is part of what makes GCA tricky to catch early. The more specific red flags tend to develop shortly after.
A new, persistent headache concentrated around the temples is the hallmark symptom. Pain and tenderness over one or both temples, particularly when you touch the area or rest your head on a pillow, should prompt evaluation. Jaw pain that worsens with chewing (called jaw claudication) is one of the strongest clinical predictors of GCA. Some people also experience tongue pain while eating.
Visual changes are the most urgent warning sign. Double vision, blurred vision, or sudden loss of vision in one eye can signal that the inflamed arteries are cutting off blood supply to the optic nerve. This is the complication doctors are racing to prevent. Other symptoms include dizziness, problems with coordination, and morning stiffness in the shoulders or neck. Between 50% and 70% of people with GCA also have polymyalgia rheumatica, a related condition causing widespread muscle pain and stiffness.
Blood Tests: The First Step
When a doctor suspects GCA, two blood tests are ordered immediately. The erythrocyte sedimentation rate (ESR) measures how quickly red blood cells settle to the bottom of a test tube, which reflects inflammation levels. An ESR of 50 mm/hour or higher is a significant finding. C-reactive protein (CRP), another marker of inflammation, is also checked, with levels at or above 10 mg/L considered elevated.
These tests are sensitive but not specific. Plenty of other conditions raise inflammation markers, so elevated results support the diagnosis but don’t confirm it on their own. On the other hand, normal results make GCA less likely, though they don’t completely rule it out.
Physical Examination Findings
During a physical exam, your doctor will feel both temporal arteries, which run along the sides of your forehead just in front of your ears. In GCA, these arteries may feel thickened, ropy, or tender. The pulse may be weak or absent on the affected side. Scalp tenderness, particularly along the path of the artery, is another common finding. Your doctor will also check your vision and may examine the back of your eyes with an ophthalmoscope to look for signs of reduced blood flow.
Temporal Artery Biopsy
A biopsy of the temporal artery has long been the gold standard for confirming GCA. The procedure is done under local anesthesia as an outpatient. A surgeon makes a small incision near the temple, removes about 3 centimeters of the artery, and sends it to a lab where a pathologist examines it under a microscope for the characteristic pattern of inflammation, including the “giant cells” that give the disease its name.
The biopsy carries a significant limitation: GCA doesn’t always affect the artery continuously. Inflammation can occur in patches, so a biopsy might sample a normal-looking segment while diseased tissue sits a few centimeters away. This is why surgeons aim for a 3-centimeter specimen and why some doctors order biopsies on both sides when suspicion is high and the first comes back negative.
One critical point: treatment should never be delayed to wait for a biopsy. Steroid treatment is started as soon as GCA is suspected, and the biopsy remains accurate for up to four weeks afterward. A large retrospective study found no statistical difference in positive biopsy rates between patients who had already started steroids and those who hadn’t (35% vs. 31%). The British Society for Rheumatology recommends performing the biopsy within one week of starting steroids but notes it can remain positive for two to six weeks after treatment begins.
Ultrasound and the Halo Sign
Ultrasound of the temporal arteries has become an increasingly important diagnostic tool, and in some centers it’s used as the first-line imaging test. The key finding is the “halo sign,” a dark ring around the artery wall that represents swelling. This sign is visible in real time, requires no radiation, and can be performed in a clinic.
A Cochrane review comparing ultrasound to biopsy found that the two tests perform similarly. Ultrasound had a median sensitivity of 75%, while biopsy had a median sensitivity of 73%. In the 2022 diagnostic scoring system from the American College of Rheumatology, a positive halo sign on ultrasound carries the same weight as a positive biopsy: both earn the maximum 5 points toward diagnosis.
Ultrasound works best when performed by an experienced operator with proper equipment. Its accuracy depends heavily on who is holding the probe, which is why availability varies between institutions.
Advanced Imaging for Larger Vessels
GCA doesn’t always limit itself to the temporal arteries. In some patients, it affects the aorta and its major branches, a pattern called large-vessel GCA. When doctors suspect this broader involvement, or when symptoms don’t fit the classic temple-headache pattern, more advanced imaging comes into play.
PET/CT scanning detects areas of active inflammation by tracking the uptake of a sugar-based tracer throughout the body. A meta-analysis of six studies found PET had 80% sensitivity and 89% specificity for diagnosing GCA, with an excellent negative predictive value of 88%, meaning a negative scan makes GCA quite unlikely. The scan is most accurate when performed before steroid treatment or within the first three days, since steroids rapidly dampen the inflammation PET detects.
CT angiography and MR angiography can also reveal thickened, inflamed vessel walls and are particularly useful for monitoring involvement of the aorta over time. PET/MRI, a newer combined approach, reduces radiation exposure and provides better tissue detail, which is especially valuable for younger patients or those needing repeated scans.
How the Scoring System Works
The 2022 classification criteria from the American College of Rheumatology use a point-based system. A patient aged 50 or older who scores 6 or more points is classified as having GCA. The points break down as follows:
- 5 points: Positive temporal artery biopsy or halo sign on ultrasound
- 3 points: ESR of 50 or higher, or CRP of 10 or higher; sudden visual loss
- 2 points: New temporal headache, scalp tenderness, jaw or tongue claudication, morning stiffness in the shoulders or neck, abnormal temporal artery on exam, or characteristic findings on advanced imaging
This means a patient with a positive biopsy (5 points) and elevated inflammation markers (3 points) would easily meet the threshold. But a patient without a biopsy could still be classified through a combination of clinical features, blood work, and imaging, which reflects how diagnosis works in practice when biopsy results are inconclusive or unavailable.
Conditions That Mimic GCA
Several conditions produce symptoms that overlap with temporal arteritis, and ruling them out is part of the diagnostic process. New-onset headaches in older adults can stem from migraines, sinus disease, dental problems, or even shingles affecting the trigeminal nerve. Jaw pain can come from dental issues or temporomandibular joint problems rather than inflamed arteries.
Other forms of vasculitis can closely mimic GCA. Takayasu arteritis affects large vessels in a pattern that can look nearly identical to large-vessel GCA, though it typically strikes younger patients. Granulomatosis with polyangiitis and polyarteritis nodosa occasionally involve the temporal arteries. Sudden vision loss has its own broad list of causes, including blood clots in the retinal arteries or veins, which need to be distinguished from GCA-related vision loss.
Amyloidosis, a rare condition where abnormal proteins build up in tissues, can occasionally affect the temporal arteries and even cause jaw claudication, making it a particularly tricky mimic. The biopsy is especially helpful here, since the pathologist can distinguish the inflammatory pattern of GCA from amyloid deposits.