Clinical Insight Into a Rare Anatomical Variation: An Autobiographical Case Report of a Supernumerary Extraocular Muscle (SEOM) in a Patient With Hyperthyroidism

Abstract

In this case report, we present the rare occurrence of supernumerary extraocular muscles (SEOM) in a 35-year-old male with hyperthyroidism. SEOMs are unusual anatomical variations involving extraocular muscles that deviate from the typical muscle arrangement in the eye. While SEOMs are rare, they can have diverse clinical manifestations, including restrictive strabismus and lid abnormalities. In this case, the patient displayed right-sided lid retraction and an asymmetrical palpebral aperture, which raised concerns about a potential association with thyroid eye disease. However, imaging revealed that the SEOM was anatomically connected to the superior rectus muscle, possibly contributing to the observed lid retraction. Understanding the complexities of SEOM and its potential interactions with conditions like thyroid ophthalmopathy is crucial for accurate diagnosis and management. Further research is needed to fully comprehend the development and clinical impact of SEOMs due to their rarity and limited knowledge in the medical literature.

Keywords: hyperthyroidism; lid retraction; ocular anomaly; optic nerve compression; restrictive strabismus; supernumerary extra ocular muscle; thyroid eye disease (ted).

Figure 1. Nine-gaze photo showing lid retraction of the right eye in the primary position and no ocular restrictions in other gazes

Figure 2. Coronal view of a plain computed tomography showing the orbit of the patient with an elongated tubular structure seen (red arrow) lateral to the right optic nerve extending from the superior rectus to the inferior rectus muscle

Figure 3. Saggital view of a plain computed tomography showing the orbit of the patient with an elongated tubular structure seen (red arrow) just behind the globe, extending from the superior to inferior rectus muscles

Figure 4. Axial view of a T1-weighted MRI pre-contrast showing an abnormal round structure (red arrow) located just behind the right globe and lateral to the optic nerve

Figure 5. Axial view of a T1-weighted MRI post-contrast highlighting the same structure (red arrow) seen in Figure 4

Figure 6. Coronal view of a T1-weighted MRI showing an abnormal, elongated, round structure (red arrow) running between the superior and inferior rectus muscle just lateral to the right optic nerve with a clear fat plane seen between both structures