Evaluation of diagnostic procedures, visual outcome and optic nerve morphology in giant cell arteritis

Abstract

The only aspect of giant cell arteritis (GCA) that is not controversial is that it 'ranks as the prime medical emergency in ophthalmology' Jennings GA. Arteritis in the temporal vessels. Lancet 1938;1:424-428. There is no other clinical scenario where the ophthalmologist, through astute diagnosis and timely intervention, can make the difference between sudden profound irreversible bilateral blindness and the retention of useful sight. GCA is a systemic necrotizing vasculitis that has a large and variable spectrum of potential signs or symptoms, and often an elusive clinical presentation. Although several serological markers, such as erythrocyte sedimentation rate and C-reactive protein may suggest the diagnosis of GCA, there is no single laboratory investigation that can confirm it. The diagnosis of GCA is confirmed by identifying characteristic histological changes of the disease in an arterial segment, such as the superficial temporal artery. However, even histological specimen may miss the diagnosis because of the presence of 'skip lesions', areas of artery in which there is no inflammation. The first of the three sections of this work explore areas of diagnostic tests of GCA that can potentially result in improved sensitivity and specificity: the role of increased platelets as a laboratory investigation to diagnose GCA, whether bilateral temporal artery biopsies provide any additional information in confirming a diagnosis of GCA, and the effect of formalin fixation on the biopsy specimen. Visual loss is one of the most devastating complications of GCA. Once visual loss occurs it tends to be profound. However, conflicting data is available on the potential for recovery of lost vision and the ultimate prognosis in these severe cases of GCA. Through both retrospective and prospective studies, the second section of this work evaluates both visual recovery and deterioration in patients with GCA. The third section of studies examines the morphological appearance of the optic nerve following an event of arteritic anterior ischemic optic neuropathy (AAION) - the most common cause of blindness from GCA. Following an ischemic insult, most non-glaucomatous optic neuropathies show pallor of the optic nerve. There is contradictory and inadequate data on whether the optic nerve appearance following an event of AAION shows this classic appearance or whether it exhibits a distinctive pattern of change unlike other optic neuropathies. This question was answered through both qualitative and quantitative assessment of the optic nerve head morphology. The first documented use of scanning laser technology (with the Heidelberg Retina Tomograph) was employed to evaluate the morphological changes of the optic nerve. It is hoped that by addressing these unanswered questions, this work will make a valuable contribution towards improving the quality of care for patients who suffer from GCA.