Description
Giant cell arteritis (GCA) is the most common vasculitis in humans. It can affect arteries of all sizes, especially the temporal, vertebral and posterior ciliary arteries. Involvement ofthe latter, as in arteritic ischemic optic neuropathy (AION), can cause severe and irreversible loss of vision.
Occlusion of the central retinal or branch retinal arteries can also occur.
Arteries containing abundant elastic tissue are preferentially involved in GCA. For this reason, the temporal artery is highly susceptible, and intracranial arteries are usually spared. Histological examination reveals granulomatous inflammation with disruption of the internal elastic lamina. Characteristic giant cells are present in two-thirds of cases.
Symptoms
The classic symptom of AION is sudden,painless, monocular and severe visual loss. This may be preceded by transient visual obscurations or flashing lights. Systemic symptoms often precede ocular symptoms, and include anorexia, fever and lowered mood. Polymyalgia rheumatica, characterized by proximal muscle pain and stiffness, is typically worse in the morning and after exercise. Scalp tenderness and headache are common. Jaw claudication (pain with chewing or speaking, resulting from ischemia of the masseteer muscles)is virtually pathognomonic
Signs
A relative afferent pupillary defect is common. Visual field defects are usually altitudinal or central. The optic disc first becomes pale and swollen, often with\ flame-shaped hemorrhages at the margin. There may also be signs of central retinal artery occlusion, including retinal pallor and a cherry-red spot at the foveola. Over the next several weeks, optic disc swelling
recedes and disc atrophy progresses.
In some patients, the ipsilateral temporal artery is palpable, tender and\ non-pulsatile. Cranial nerve palsies (most often of the sixth nerve) have also been described.
Prevalence
Arteritic ischemic optic neuropathy is very uncommon in patients under 60 years of age.
Significance
Giant cell arteritis is a medical emergency because progression to bilateral blindness can occur rapidly.
Differential diagnosis
Non-arteritic ischemic optic neuropathy; Optic neuritis; central retinal artery occlusion; central retinal vein occlusion.
See also
Amaurosis fugax.
Management
Urgent Giant cell arteritis is a medical emergency. Visual loss in AION can be rapid and is usually permanent, so the aim of treatment is to prevent blindness in the other eye.
Blood tests and pathology Urgent erythrocyte sedimentation rate (ESR) is measured whenever this diagnosis is suspected. The level is often above 60 mm/h. As a rough guide, the upper limit of normal is approximately half the patient’s age in years. As about 20 per cent of patients with biopsy-proven GCA have a normal ESR, clinical suspicion is indispensable. The C-reactive protein level is invariably raised.
Medications An intravenous corticosteroid, usually methylprednisolone, is commenced immediately when GCA is suspected. If the temporal artery biopsy is positive, oral prednisolone is continued.
Fig. 12.1
Swollen optic disc and macular area in arteritic ischemic optic neuropathy.
Fig. 12.2
Fluorescein angiogram of the same patient as in Fig. 12.1, showing choroidal hypoperfusion.
If the disease is not found in adequate biopsy specimens, steroids are usually ceased – unless clinical suspicion is high and a response to treatment has been observed. Notably, unnecessary administration of corticosteroids may cause substantial morbidity.
Surgery Temporal artery biopsy is usually performed within a few days of presentation, because the histological features of GCA may recede after more than a week of corticosteroid treatment. Biopsy is particularly important when
steroids are relatively contraindicated, as in patients with diabetes. A negative biopsy result does not completely exclude the diagnosis of GCA.
Ocular tests and imaging investigations
Ocular pneumoplethysmography, looking for reduced ocular blood flow, may be considered.
Review The steroid dose is tapered slowly, with monitoring of symptoms and ESR. Treatment is continued for at least 6 months.