An 82-year-old man was referred to the Diagnostic Imaging Center with progressive bilateral ocular motility impairment and diplopia, which had gradually worsened over the past three months, with notable difficulty in upward gaze. Orbital magnetic resonance (MR) imaging was performed, which showed symmetric enlargement of the muscle bellies of both inferior rectus muscles (Fig. 1A and 1B). Coronal fat-suppressed T2-weighted images revealed hyperintense signals within these muscles, indicating active inflammatory change (Fig.
