201. Magnetic Resonance Imaging of Orbital and Scalp Arteries in Patients with Cranial Giant Cell Arteritis
Creators: name: Rennie Rhee1,
name: Vatsal Bhatt1
name: Shubhasree Banerjee1
name: Madhura A. Tamhankar1
name: Amudala1, Naomi
name: Chou1, Sherry
name: Burke1, Morgan
name: Merkel1, Peter A.
name: Song1, Jae W.
Publisher: name: Zenodo
Year: 2022
Subjects: Vasculitis
ANCA
Abstracts
Giant Cell Arthritis
MPA
GPA
EGPA
Takayasu
IgA vasculitis

description: <strong>Background:</strong> In giant cell arteritis (GCA), there is a critical need to identify patients at risk for vision loss. MRI evaluates neurovascular anatomy posterior to the ocular globe, an area not visualized by ophthalmologic examination. Multiple case series and small cohort studies demonstrated that MRI can detect inflammation of orbital arteries in GCA-related ischemic optic neuropathy (“ocular GCA”). The aim of this study was to investigate MRI enhancement of orbital and scalp arteries in patients with suspected cranial GCA, including patients with or without visual symptoms. <strong>Methods:</strong> Patients with suspected new or relapsing cranial GCA who underwent orbital and brain vessel wall MRI at presentation were included in the study. A clinical diagnosis of ocular or non-ocular GCA was determined by a rheumatologist and/or ophthalmologist and confirmed retrospectively. All MR images were scored by a single radiologist blinded to clinical data. Semi-quantitative integer scores of MRI enhancement were determined: 8 orbital structures were each scored 0, 1, or 2 (score 1-2 defined as abnormal) and included bilateral optic nerve sheath, optic nerve, intraconal orbital fat, and retrobulbar fat of posterior globe; 8 scalp arteries were each scored 0, 1, 2, or 3 (score 2-3 defined as abnormal) and included bilateral temporal arteries (stem, frontal, and parietal branches) and occipital arteries. MRI was considered diagnostic for GCA if at least 1 scalp and/or orbital artery had abnormal enhancement. A subgroup of patients with a clinical diagnosis of GCA underwent repeat MRI at month 1 to assess post-treatment changes in the composite orbital score (summation of scores for all bilateral orbital structures, possible range 0-16). Differences in MRI findings between groups were determined using Fisher’s exact or Wilcoxon signed-rank test. <strong>Results: </strong>The study included 30 patients with suspected cranial GCA: 25 new and 5 relapsing GCA. Of 30 patients, 11 had a clinical diagnosis of active GCA: 8 non-ocular and 3 ocular GCA. Of the 9 new diagnoses, 6 patients had a temporal artery biopsy consistent with GCA and 3 patients had negative biopsy. Compared to a clinical diagnosis of GCA, MRI had sensitivity of 83% (95% CI 52% to 98%), specificity of 94% (95% CI 73% to 99%), positive likelihood ratio of 15 (95% CI 2 to 102), and negative likelihood ratio of 0.18 (95% CI 0.05 to 0.63) for the diagnosis of GCA. Orbital enhancement on MRI was observed in 100% of patients with ocular GCA, 38% non-ocular GCA, and 11% without GCA (P &lt; 0.01). Example MR images are shown in Figure 1B. Among 6 patients with an abnormal orbital MRI and a clinical diagnosis of GCA, all 6 patients had bilateral orbital enhancement including 3 patients without visual symptoms, 1 patient with unilateral visual symptoms, and 2 patients with bilateral visual symptoms. Follow-up MRIs were performed in 8 patients: all patients with orbital enhancement at baseline (n=4) had decreased composite orbital scores after 1-month treatment with glucocorticoids (median composite orbital score: baseline = 6 [IQR 4.5-6] and 1-month = 3 [IQR 2-5]). <strong>Conclusions:</strong> Vessel wall MRI of orbital and scalp arteries is a sensitive and specific diagnostic test for active cranial GCA. This study not only confirmed the presence of orbital MRI enhancement in patients with ocular GCA, similar to previous studies, but also is the first to demonstrate orbital MRI abnormalities in GCA patients without visual symptoms. These data validate the utility of cranial MRI for the diagnosis of GCA and generates a new hypothesis: orbital MRI detects “at-risk” subclinical ocular disease and may be a predictive biomarker of impending blindness due to GCA. Future studies may determine if cranial MRI can be used for risk stratification and treatment decision-making (e.g., high- vs low-dose glucocorticoids) as well as longitudinal disease surveillance in GCA. <strong>Disclosures:</strong> MAT – consultant for Horizon pharmaceuticals, UpToDate