Contributor: Gordon K. Klintworth
Temporal arteritis (cranial arteritis, giant cell arteritis) is a granulomatous arteritis[arteritis - granulomatous] of the aorta and its major branches. There is a predilection for the extracranial branches of the carotid artery and especially the temporal artery. Myalgia rheumatica is often associated. The condition usually occurs in persons > 50 years old. The ophthalmoscopic manifestations include central retinal artery occlusion, anterior ischemic optic neuropathy, cotton-wool spots, and hemorrhage. Delayed filling of the retinal and choroidal vessels may be evident on  fluorescein angiography. Involvement of  the short ciliary arteries by the occlusovascular disease may result in a deficient vascularity of the choroid and choroidal infarction. Giant cell arteritis is one of the most common causes of optic nerve infarction. Prior to glucocorticoid therapy ~ 14% of patients had a permanent loss of vision. Vision loss after glucocorticoid therapy is low (~1%). The probability of visual loss is greater in patients with visual loss prior to the onset of therapy. A permanent loss of vision may follow ischemic optic neuropathy from involvement of the arteries supplying the anterior portion of the optic nerve. Visual loss can also occur because of central retinal artery occlusion, macular hemorrhage [hemorrhage - macula] or occipital infarction. The adventia and media of affected arteries have granulomatous inflammation and patchy areas of necrosis containing plasma cells and lymphocytes. The lamina elastica is typically fragmented and this region of the vessels contain multinucleated giant cells and macrophages. Portions of the vascular lumen are narrowed by proliferating endothelial cells and thrombus.
Anorexia, weight loss, headache, leukocytosis, fever, and an elevated erythrocyte sedimentation rate are usually present. When one eye is affected the other eye becomes involved within a few weeks in ~50% of cases.
An early ophthalmoscopic finding is a pale and swollen optic nerve head  from ischemic optic neuropathy [optic neuopathy - ischemic] and this is commonly followed by an atrophic optic nerve head. The temporal arteries become swollen painful and tender, and swollen.
The diagnosis can be established by finding granulomatous inflammation in the wall of a biopsied temporal artery and this reaction is often accompanied by thrombosis.  The differential diagnosis of temporal arteritis includes Wegener granulomatosis and various types of necrotizing vasculitis (Churg-Strauss syndrome, micropolyangiitis, rheumatoid vasculitis [vasculitis - rheumatoid], cryoglobulinemic vasculitis, polyarteritis nodosa). Infarction of the optic nerve in association with occluded short posterior ciliary arteries affects the optic nerve mainly at or immediately posterior to the lamina cribrosa. Features of the affected tissue in an acute infarct include liquefaction necrosis of the axons and phagocytosis of the necrotic debris. Hyaluronic acid may be present in the area of necrosis when the infarct affects the optic nerve head anterior to the lamina cribrosa. This resembles the cavernous optic atrophy [optic atrophy - cavernous] of  glaucoma and the hyaluronic acid is presumably comes from the vitreous that is displaced posteriorly into the optic nerve head through defects in the prelaminar glial membrane.