Diagnostic and surgical techniquesThe role of vascular ultrasound in managing giant cell arteritis in ophthalmology
Introduction
Giant cell arteritis (GCA) is the most common systemic vasculitis in the elderly8 and predominantly occurs in whites.50 Those of Scandinavian descent are at an increased risk, and familial aggregations of GCA have been observed.18 GCAis a potentially life-threatening ophthalmic emergency that can result in irreversible blindness without prompt treatment.39 Advancing age, peaking at 70–79 years, female gender, and an underlying diagnosis of polymyalgia rheumatica are associated risk factors in British populations.37 Visual loss can occur unilaterally or bilaterally, occurring in 20% of patients as partial or complete presentations.48
The diagnosis of GCA is challenging owing to its protean manifestations of cranial and extracranial disease, difficulties in interpretation of blood results, and nonspecific ophthalmic symptoms. Very often, the ophthalmic examination is completely normal until catastrophic visual loss from anterior ischemic optic neuropathy. Sudden-onset unilateral visual loss, associated with a relative afferent pupillary defect and a pale, swollen optic nerve, is a classic presentation of arteritic ischemic optic neuropathy, which is typical of GCA. Patients often experience other symptoms, however, including transient monocular blindness, transient visual blurring, double vision. These symptoms are not specific to GCA; however, they may raise the suspicion of the diagnosis, especially in the context of headaches, jaw claudication, raised inflammatory markers, and advanced age.
Challenges arise when elderly patients present with vague symptoms, are poor historians, or may have other reasons for their ocular symptoms, such as carotid artery disease, early Herpes zoster ophthalmicus, or general malaise from systemic infection or malignancy. In some cases, blurred vision is attributed to vitreous detachment. Nonarteritic anterior ischemic optic neuropathy is another condition that may lead to a false diagnosis of GCA. In this case, cardiovascular risk factors and fluctuations in blood pressure are thought to lead to a watershed infarct of the optic nerve, leading to sectoral ischemia and consequent field loss, which is typically, but not always, altitudinal.
The treatment of GCA with ocular involvement is high-dose systemic corticosteroids, starting with either intravenous methylprednisolone or high-dose oral prednisolone, tapering slowly over several months to years. Although high-dose steroids are justified in confirmed cases where the diagnosis is clinically evident, a significant proportion of patients are treated for suspected GCA on the basis of nonspecific visual symptoms, headaches, and elevated inflammatory markers. This is the result of the great difficulty in confirming a diagnosis based on symptoms, history, examination, and blood results in the acute setting and the concern about the possibility of visual loss. This group of patients with ocular symptoms is generally referred to the emergency eye services, where, in the United Kingdom, they are often managed by the “on-call” ophthalmology team.
In view of the challenge of diagnosis, patients with a suspected diagnosis are commonly started on high doses of systemic steroid while awaiting a definitive histological diagnosis. After being on such treatment for more than 2–3 weeks, steroids are then tapered slowly over 18–24 months, resulting in a high cumulative dose. Commonly, even when a diagnosis is excluded with a negative biopsy, steroid taper is often required, leading to unnecessary steroid exposure.
American College of Rheumatology (ACR) guidelines include temporal artery biopsy (TAB) as one of the five diagnostic criteria, of which at least three must be present to make a diagnosis of GCA.23 In the past, TAB has been considered the gold standard for the diagnosis of GCA, and the consensus has been that this should always be performed without delaying treatment.22,27,39 This practice has been supported by the guidelines from the British Society of Rheumatology, British Health Professionals in Rheumatology, and the 2014 National Institute of Clinical Excellence.11,34
Vascular ultrasound (US) is shown to be a well-tolerated, safe, and cost-effective investigation with a proven role in the diagnosis of GCA.7,27,41 The recent 2018 EULAR recommendations advocate US examination of the temporal arteries with or without axillary artery examination as a first-line investigation in patients with suspected predominantly cranial GCA.13 As such, there is a clear need to incorporate vascular US examination into ophthalmic practice as patients with suspected cranial GCA are regularly referred to ophthalmologists. We review the literature to date and the rationale to incorporate vascular US into the ophthalmology repertoire.
Section snippets
Temporal artery biopsy
TAB has an established role in confirming GCA and is regarded by many as the “reference standard,” providing histological evidence for the diagnosis. TAB is performed under local anesthetic by surgical specialists, including ophthalmologists, general surgeons, vascular surgeons, and neurosurgeons.17,30 The temporal artery is a terminal continuation of the external carotid artery that begins in the parotid gland posterior to the neck of the zygomatic process of the temporal bone and divides
Overview of vascular US in the assessment of patients with suspected large vessel vasculitis
US examination is a noninvasive, safe, and efficient imaging modality that can take cross-sectional images of vessels and evaluate vascular flow dynamics.41 Rheumatologists routinely employ US as a useful tool to facilitate diagnoses.42 Four pathological lesions are evident on US when assessing vessels. These include arterial wall thickening depicted as a “halo” on longitudinal imaging, noncompressible arteries on transverse imaging, stenosis, and vessel occlusion.41
In patients with GCA, it has
Equipment requirements and settings
Modern US machines equipped with linear probes with a gray scale frequency of at least 15 MHz and color Doppler mode of at least 6 MHz are appropriate for investigating GCA.32 Probes of 20 MHz or more permit visualization of the intima-media complex in normal subjects.41 Such equipment is not routinely found in the eye department, where a standard ophthalmic ultrasound does not include high frequency probes or color Doppler; however, the high frequency probes will enable good resolution for
TAB versus vascular US
Vascular US has become the first choice in a number of centers, where the need for TAB has subsequently been reduced.41 In cases where clinical suspicion is high but the ultrasound is nonconfirmatory, TAB is still indicated. A GCA probability score developed by Laskou and coworkers has outlined an algorithm that best utilizes US, TAB, and other imaging modalities in the context of individual clinical presentations.26
The key benefits of US over TAB relate to cost and time savings. The TABUL
The role of GCA “fast-track” clinics in rheumatology
Inspired by other fields in medicine including stroke and cardiology, the introduction of GCA fast-track clinics (FTCs) into rheumatology has been shown in two separate studies to significantly reduce visual loss compared to the conventional approach.15,36 The GCA FTC approach uses the immediate use of US on the temporal, axillary, and carotid arteries alongside a history, physical examination, and laboratory tests. Treatment is instated without delay where there is a high clinical suspicion
Incorporating vascular US into ophthalmology practice
TABs are generally added onto elective operating lists or performed outside of normal working hours, given the likely importance of timing and detection on pathological analysis. Ophthalmologists routinely perform B-scan ultrasound in the eye casualty or retinal clinics for assessment of retinal detachment, vitreous hemorrhage, or ocular tumors, among other diagnoses. Incorporating vascular US as a new diagnostic test into the ophthalmologists' skill set would complement anterior segment,
Conclusions
Suspected GCA remains a highly challenging diagnosis presenting to the ophthalmologist. Despite existing guidelines, patients are still at risk of visual loss given ambiguity in clinical presentation, difficulties in interpretation of blood results, and often delays in obtaining TAB. The role of ophthalmologist in delivering US in the workup of GCA should be investigated in the acute ophthalmic setting, given its proven effectiveness as a diagnostic test, safety profile, cost-effectiveness, and
Methods of literature search
A search was performed using the search terms “giant cell arteritis” and “ultrasound” inputted into Embase and Embase Classic (1947 to January 2017) and Ovid Medline In-Process & Other Non-Indexed Citations (1946 to Present). Further relevant articles were handpicked and included if they alluded to the use of vascular ultrasound as a diagnostic adjunct for giant cell arteritis.
Disclosures
There are no disclosures to report.
Acknowledgments
The authors would like to thank Dr Chetan Mukhtyar, MBBS, MSc, MD, FRCP (Edin), a consultant rheumatologist in Norfolk and Norwich University Hospital, who kindly provided images of the halo sign as shown in Fig. 1.
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