Acquired Brown syndrome due to isolated superior oblique involvement secondary to thyroid ophthalmopathy: A rare case report

Acquired Brown syndrome is an uncommon ocular motility disorder characterized by impaired elevation of the eye in adduction due to restriction of the superior oblique tendon–trochlea complex. Its association with thyroid ophthalmopathy is rare. Here, we report a case of a 44-year-old woman with a history of hyperthyroidism and hypertension who presented with 15 days of periocular pain in the right eye and diplopia in levo-elevation and up-gaze. Clinical examination revealed limited elevation in adduction with a positive forced-duction test. Imaging showed inflammatory changes near the superior oblique tendon, along with features of thyroid ophthalmopathy, only in the right superior oblique. The patient was managed conservatively with lifestyle modifications. Systemic medication for thyroid ophthalmopathy was continued to maintain disease control, and the patient was kept under close follow-up to monitor for spontaneous improvement. This case report highlights the importance of recognizing atypical presentations of thyroid ophthalmopathy and considering neuroimaging when a patient presents with painful restriction and diplopia.