Extraocular muscle enlargement of indeterminate cause in pediatric patients: case series and literature review.

Purpose: To specify the clinical characteristics of enlarged extraocular muscles of indeterminate cause in pediatric patients based on a case series and literature review.

Methods: The medical records of pediatric patients who presented between January 2019 and January 2022 with enlarged extraocular muscles, where the underlying cause could not be determined, were retrospectively reviewed.

Results: Four patients were included. The main reason for presentation was evaluation of abnormal head posture. Head tilt or turn with duction deficit was observed in all patients. The age of onset ranged from 6 months to 1 year. Two patients presented with esotropia and hypotropia; the other 2 patients, with large-angle esotropia. Orbital imaging was performed in all cases and revealed unilateral rectus muscle enlargement sparing the muscle tendon. All 4 patients were found to have an enlarged medial rectus muscle. In the 2 patients with hypotropia, the inferior rectus muscle was also involved. No underlying systemic or orbital disease was found. There were no changes in the orbit or extraocular muscles on follow-up imaging test. The intraoperative forced duction test revealed severe restriction in the direction of gaze opposite to the primary field of action of the enlarged muscles.

Conclusions: Enlargement of extraocular muscles should be considered in the differential diagnosis when large-angle incomitant vertical or horizontal misalignment and abnormal head posture are observed in infancy.