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Ophthalmic Pearls: Neuro
Diagnosis and Treatment of Giant Cell Arteritis
Giant cell arteritis presents a genuine ophthalmic emergency, as it carries a high risk of visual loss in one or both eyes. Ophthalmologists must act promptly to make the clinical diagnosis, start high-dose corticosteroid treatment and confirm the diagnosis with a temporal artery biopsy.
Giant cell arteritis (GCA), also called temporal arteritis, is a systemic inflammatory vasculitis that affects medium- to large-sized arteries. The incidence of GCA ranges from 10 to 30 cases per 100,000 population in individuals aged 50 and older.1 Persons of Scandinavian and Northern European descent have the highest incidence of the disease; African-Americans, Hispanics and Asians are at lower risk.1
Signs and Symptoms
Systemic symptoms. The classic symptoms of GCA include headache, scalp tenderness, jaw claudication, neck pain, fever, chills, myalgia, weight loss and fatigue.
GCA often occurs simultaneously with polymyalgia rheumatica (PMR), which is a systemic inflammatory disease characterized by moderately elevated inflammatory markers and myalgias of the neck, shoulder and pelvic girdle. About 40 to 50 percent of those with GCA have concurrent PMR manifestations, and 9 to 21 percent of those who are initially diagnosed with PMR have a positive biopsy for GCA.1
Visual symptoms. Ophthalmic symptoms—including amaurosis fugax, diplopia and sudden permanent visual loss—manifest in approximately 25 percent of patients with GCA.1,2
Permanent visual loss is the most concerning complication of GCA. Typically, it is preceded by several days or weeks of transient visual or systemic symptoms. In addition, unilateral visual loss may progress to bilateral involvement within days.
Ocular ischemic consequences associated with GCA include anterior ischemic optic neuropathy (AION), posterior ischemic optic neuropathy, central retinal artery occlusion, choroidal ischemia and posterior visual pathway infarctions.2 AION is the most common cause of visual loss in GCA. On examination, it is often characterized by a pallid or chalky white appearance of the affected optic nerve head.2 In contrast, the optic nerve edema in nonarteritic anterior ischemic optic neuropathy, which is not caused by GCA, typically is hyperemic.
It should be noted that some 20 percent of patients have ophthalmic symptoms without any accompanying systemic symptoms; this variant is called occult GCA.3
Laboratory findings. Blood samples should be taken to test for the presence of the inflammatory markers erythrocyte sedimentation rate (ESR), C-reactive protein and platelet count, which are typically elevated in patients with GCA.
However, the clinician cannot rely solely on elevated inflammatory markers, as 10 to 20 percent of patients with GCA can have a normal ESR.2 Thus, it is important to confirm a working diagnosis of GCA with a temporal artery biopsy (TAB) as soon as is feasible, preferably within two weeks of initiating corticosteroid treatment.
Biopsy and histopathology. Ophthalmologists are most frequently called upon to perform TAB, although other specialists also perform the procedure. Inflammatory changes in the artery may be discontinous, with so-called skip areas occurring in approximately 8 percent of cases.2 Thus, to avoid missing such changes, it is helpful to obtain a long section of artery (at least 2 cm) and to perform serial sectioning. Typically, a unilateral TAB is sufficient. However, in cases of high clinical suspicion and a negative unilateral TAB, a contralateral TAB is recommended.
Although TAB is a safe procedure with relatively few contraindications, one must be mindful of the anatomy to avoid damage to branches of the facial nerve, which lie beneath the superficial temporal artery and its fascia.
On histopathologic examination of the artery, the inflammatory process involves all layers of the arterial wall; the polymorphic cellular infiltrate includes T lymphocytes and macrophages. 4
Multinucleated giant cells may be identified adjacent to the internal elastic lamina, although their presence is not necessary to confirm the diagnosis (Figs. 1 and 2).
Management of Suspected GCA
Although there is no established protocol for treating suspected GCA, the general recommendation is to start oral prednisone in cases of moderate to high clinical suspicion and IV methylprednisolone in patients with visual loss.
Because of the potential for serious consequences, the clinician should not wait for biopsy results before initiating corticosteroid treatment in cases of moderate to high clinical suspicion for GCA. If clinical suspicion is low, it is reasonable to hold off on corticosteroid treatment until prompt TAB can be performed.
Once the diagnosis has been confirmed pathologically, the tapering regimen and duration of treatment are guided by the clinical manifestations and laboratory findings. An initial low corticosteroid dose or a rapid corticosteroid taper can lead to incomplete remission or recurrent disease activity and the potential for visual loss.
Because GCA occurs in an older population, which is often affected by comorbidities such as diabetes mellitus, patients must be monitored closely by their primary care physician for adverse side effects related to corticosteroid therapy.
GCA can be a challenging diagnosis to make because of its nonspecific clinical and laboratory findings. Ophthalmologists must be alert to the possibility of GCA in older patients with headaches and visual loss. Prompt treatment with corticosteroids and confirmation of the diagnosis with a TAB are necessary for preservation of sight.