This site uses tracking information. Visit our privacy policy. Click to agree to this policy and not see this again.

Ophthalmology and Visual Sciences

Enlarged muscle bellies in thyroid eye disease

Enlarged muscle bellies in thyroid eye disease

Category(ies): Neuro-ophthalmology, Oculoplastics
Contributor: Elizabeth Gauger, MD

Thyroid eye disease (TED) is the most common cause of unilateral or bilateral proptosis in adults. It occurs most commonly in patients who are hyperthyroid. However, it may also occur in patients who are hypothyroid or even euthyroid.

The characteristic finding on CT scan is enlargement (due to inflammation and fibrosis) of the extraocular muscle bellies. The muscle tendon is typically spared. The muscles most commonly enlarged in TED are the inferior rectus followed by the medial rectus, although any of the muscles may be involved. It can contribute to vision loss by causing a compressive optic neuropathy.

This patient is a 60-year-old female who has severe TED and has already has undergone bilateral orbital decompression (please note that the orbital floor and lateral orbital wall show areas of bony discontinuity).

Axial CT scan showing enlarged muscle belly in Thyroid Eye Disease
Figure 1. Axial CT scan showing enlarged muscle belly in Thyroid Eye Disease. The medial rectus muscle is marked "MR"
Coronal CT scan showing the enlarged muscle bellies in cross section
Figure 2. Coronal CT scan showing the enlarged muscle bellies in cross section. The medial rectus muscle is marked "MR" and the inferior rectus is labled "IR"