A Comprehensive Narrative Review of Extracranial Vessel and Orbital MRI Findings in Giant Cell Arteritis.

A comprehensive narrative review of the superficial extracranial artery and orbital features on magnetic resonance imaging (MRI) in giant cell arteritis (GCA) is presented. A search on PubMed, EMBASE and Web of Science for English-language publications detailing MRI head/orbital imaging in GCA was conducted. Inclusion criteria were patients with positive histopathology and/or meeting the 2022 American college of Rheumatology (ACR) criteria who had MRI depicting significant abnormalities of the superficial extracranial vessels and/or orbit. 51 studies were identified for inclusion: 12 studies detailing analysis of superficial extracranial vessels, and 39 studies detailing orbital abnormalities. Articles included ranged from case-reports, retrospective case-series and prospective cohort studies, with variable patient-level data available for extraction and analysis. MRI of the extracranial arteries may demonstrate similar diagnostic power to that of ultrasound and demonstrates promising sensitivity and specificity when compared to biopsy-proven cases. The orbital features on MRI may occasionally be overlooked, however key structures include the intraconal orbital fat, optic nerve and nerve sheath and ophthalmic arteries. Subtle changes may exist in these clinically significant structures and represent important features which need to be identified to facilitate expedient diagnosis or guide further investigation and appropriate treatment. GCA should be a differential consideration in patients with non-specific intraconal fat inflammation and/or optic peri-neuritis, particularly if bilateral. Additionally, the concurrent presence of orbital inflammation (e.g.: optic peri-neuritis, intraconal orbital inflammation) and extracranial vessel wall inflammation should indicate a consideration of vasculitic pathology such as GCA.