[Extraocular muscle involvement in patients with thyroid-associated orbitopathy]

Area of Science:

• Ophthalmology
• Endocrinology
• Medical Imaging

Background:

• Thyroid-associated orbitopathy (TAO) is an autoimmune condition affecting the tissues around the eye.
• Extraocular muscle (EOM) enlargement is a common feature of TAO, contributing to proptosis and diplopia.
• Understanding the pattern of EOM involvement is crucial for diagnosis and management.

Purpose of the Study:

• To investigate the frequency and patterns of extraocular rectus muscle involvement in patients with TAO.
• To correlate muscle enlargement with the severity of exophthalmos.

Main Methods:

• Retrospective analysis of 154 orbits from 77 adult TAO patients.
• General ophthalmic examination, ultrasonography, and MRI of the orbit.
• Measurement of rectus muscle diameters using MRI and Spearman correlation analysis.

Main Results:

• A moderate positive correlation (r=0.514) was observed between the sum of rectus muscle diameters and exophthalmos.
• In single-muscle enlargement, superior rectus (RS) and inferior rectus (RI) muscles were most frequently affected.
• In multiple-muscle enlargement, medial rectus (RM) and inferior rectus (RI) muscles showed the highest involvement rates.

Conclusions:

• Vertical rectus muscles are predominantly involved in single-muscle enlargement in TAO.
• Medial rectus muscle is most frequently implicated in multiple-muscle enlargement.
• Superior muscle group involvement in TAO may be more common than previously reported in literature.