Why do temporal arteries go wrong? Principles and pearls from a clinician and a pathologist.

Early diagnosis and treatment of GCA is essential to prevent complications of the disease, including permanent vision loss. Temporal artery biopsy has been intrinsically linked with the diagnosis of GCA for several decades. A negative predictive value of > 90% has been reported for temporal artery biopsy; however, a negative result does not reliably indicate the absence of GCA because inflammation of the temporal artery is not always evident because of segmental involvement or other reasons. This is demonstrated by a case study of a patient hospitalized following acute vision loss to the right eye whose glucocorticoid treatment was suspended after temporal artery biopsy revealed no evidence of GCA. The patient subsequently lost sight in the left eye 6 weeks after stopping glucocorticoid therapy. The specificity of temporal artery biopsy for the diagnosis of GCA is variable and influenced by many factors, including length of biopsy specimens, vasculitis in vessels other than the temporal artery (ophthalmic, retinal and posterior ciliary vessels), unilateral versus bilateral biopsy, expertise of the surgeon, interpretation of histology, effects of treatment and confounding factors such as atherosclerosis or other non-GCA diseases that can affect the temporal artery. Considering the limitations of temporal artery biopsy, collaboration and education between the clinician, the pathologist and the patient, taking into account a thorough examination of patient history, recognizing signs and symptoms, and potentially involving newer imaging studies with trained technicians and physicians, are essential in confirming or eliminating diagnosis of GCA.