Temporal arteritis (TA), also known as Giant Cell Arteritis, is a condition characterized by inflammation of the medium-to-large arteries, most often those supplying the head and neck. This inflammation causes the blood vessel walls to swell, which narrows the inner channel and restricts blood flow. The urgency of diagnosis stems from the high risk to the eyes, as restricted blood flow to the optic nerve can lead to sudden, irreversible vision loss in about 15 to 20% of untreated cases. The diagnostic process must be initiated immediately upon clinical suspicion. Diagnosis typically involves a rapid sequence of clinical evaluation, blood tests, non-invasive imaging, and often a minor surgical procedure.
Initial Clinical Assessment
Diagnosis begins with a detailed assessment of the patient’s symptoms and medical history, looking for a cluster of classic signs suggesting arterial inflammation. The most common symptom is a new-onset headache, often severe and localized to the temporal or frontal areas.
A high degree of suspicion is raised if the patient reports pain or fatigue in the jaw muscles while chewing, known as jaw claudication. Scalp tenderness, often noticed when brushing hair or resting the head on a pillow, is another characteristic finding. Patients may also report general symptoms like unexplained fever, weight loss, or fatigue, which are signs of systemic inflammation.
The most concerning symptoms affect vision, such as temporary episodes of blurred or darkened vision (amaurosis fugax). During the physical examination, the doctor carefully palpates the temporal arteries on both sides of the head. Findings supporting the diagnosis include a thickened, nodular, or tender artery, or a pulse that feels significantly reduced or entirely absent.
Laboratory Markers of Inflammation
Blood tests are quickly ordered following the clinical assessment to measure systemic inflammation. The two primary laboratory markers used are the Erythrocyte Sedimentation Rate (ESR) and the C-Reactive Protein (CRP) level. These tests measure acute-phase reactants, which are proteins released by the liver in response to inflammation.
The ESR measures how quickly red blood cells settle in a test tube, with a faster rate indicating the presence of inflammatory proteins. In suspected cases of temporal arteritis, the ESR is typically elevated, often exceeding 50 millimeters per hour. The CRP test is generally considered a more sensitive marker that rises and falls more quickly than the ESR, making it valuable for tracking disease activity.
While elevated ESR and CRP strongly support the diagnosis, these markers are not specific to temporal arteritis and can be elevated by many other inflammatory conditions. Up to 20% of patients with confirmed TA may have a normal ESR, meaning normal lab results do not rule out the disease. Therefore, laboratory findings must always be interpreted alongside the patient’s clinical presentation and other diagnostic tests.
Non-Invasive Imaging Studies
Non-invasive imaging techniques are increasingly utilized as an early step to visualize the affected arteries without requiring surgery. The most common is the Temporal Artery Ultrasound (TAUS), often performed using Doppler technology. This quick, painless procedure uses sound waves to create images of the artery walls and measure blood flow.
The hallmark finding on a TAUS is the “halo sign,” which appears as a dark, hypoechoic thickening of the vessel wall surrounding the artery’s inner channel. This visual representation corresponds directly to the inflammatory swelling and fluid accumulation within the artery wall. The presence of a clear halo sign in a patient with classic symptoms is highly predictive of the disease.
If symptoms are atypical, or if there is concern for involvement in larger vessels like the aorta and its branches, other imaging modalities may be employed. These include Magnetic Resonance Angiography (MRA) or Positron Emission Tomography (PET) scans. These advanced techniques can reveal arterial wall thickening or narrowing in larger, more distant arteries.
The Definitive Temporal Artery Biopsy
The Temporal Artery Biopsy (TAB) remains the standard diagnostic procedure despite advances in imaging. This minor surgery is performed under local anesthetic, where a segment of the temporal artery is removed for laboratory analysis. High-dose corticosteroid treatment is typically initiated immediately upon strong clinical suspicion to minimize the risk of permanent vision loss, even before the biopsy results are returned.
The biopsy must be performed as soon as possible after starting steroids, ideally within one to two weeks, as the medication can mask inflammation over time. To ensure an accurate result, the surgeon must remove a relatively long segment of the artery, typically between one and three centimeters. This length is necessary because the inflammation is often patchy, a phenomenon known as “skip lesions.”
The removed segment is sent to a pathologist for microscopic examination. The pathologist looks for specific signs of vasculitis, including the presence of mononuclear inflammatory infiltrates, such as lymphocytes and macrophages, within the artery wall. Definitive confirmation involves identifying granulomatous inflammation and, often, large immune cells called multinucleated giant cells, which give the condition its alternate name, Giant Cell Arteritis.