Imaging of thyroid eye disease (and other extra-ocular muscle diseases)

Summary

This video delves into the conal space and extraocular muscles, crucial for eye movement. It covers their anatomy, pathology, and disorders like thyroid eye disease, orbital pseudotumor, and lymphoma. The video explains muscle involvement, symptoms, and diagnostic techniques, including the use of the Barret index for assessing optic nerve compression risk.

Takeaways

• 👁️ The conal space in the eye orbits is primarily composed of the extraocular muscles, which are responsible for eye movement.
• 💪 There are six extraocular muscles: superior rectus, inferior rectus, medial rectus, lateral rectus, inferior oblique, and superior oblique.
• 🔄 The superior oblique muscle makes a 90° turn in a small ring of cartilage tissue known as the trar apparatus.
• 📍 The levator palpebrae muscle is not responsible for eye movement but for elevating the upper eyelid.
• 🤔 The anatomy of extraocular muscles can be visualized on coronal T2-weighted images of the orbit.
• 🚨 Three key pathologies affecting the extraocular muscles are thyroid eye disease, orbital pseudotumor (idiopathic orbital inflammation), and lymphoma.
• 🌐 Thyroid eye disease is the most frequent cause of proptosis in adults, often characterized by bilateral and symmetrical enlargement of extraocular muscles.
• 🥤 The 'Coca-Cola bottle' sign refers to the thickening of extraocular muscle bellies with relative sparing of the tendons in thyroid eye disease.
• 📏 The Barret index is a quantitative method to estimate the degree of apical crowding and the risk for compressive optic neuropathy in thyroid eye disease.
• 🔎 Idiopathic orbital inflammation often presents unilaterally with acute symptoms and can involve various orbital structures, including the extraocular muscles.
• 🏥 Orbital lymphoma is the most common primary orbital tumor in older patients, often involving the extraocular muscles and characterized by diffusion restriction on MRI.

Q & A

What is the conal space in the eye orbit?

The conal space in the eye orbit refers to the area where the extraocular muscles are located, which are responsible for eye movement.

How many extraocular muscles are there, and what are their names?

There are six extraocular muscles: superior rectus, inferior rectus, medial rectus, lateral rectus, inferior oblique, and superior oblique.

What is the trar apparatus, and which muscle uses it?

The trar apparatus is a small ring of cartilage tissue where the superior oblique muscle makes a 90° turn.

What is the levator palpebrae muscle responsible for?

The levator palpebrae muscle is responsible for the elevation of the upper eyelid.

What is the annulus of Zinn, and where is it located?

The annulus of Zinn is a small ring of fibrous tissue located deep within the orbit at the orbital apex, surrounding part of the superior orbital fissure and the optic canal.

What is the significance of the annulus of Zinn in the context of extraocular muscles?

The annulus of Zinn is significant because all extraocular muscles, except the inferior oblique muscle, either insert or originate from it.

What are the three important entities of pathology that affect the extraocular muscles?

The three important entities of pathology affecting the extraocular muscles are thyroid eye disease, orbital pseudotumor (idiopathic orbital inflammation), and lymphoma of the extraocular muscles.

What is the most common cause of proptosis in adult patients?

The most common cause of proptosis in adult patients is thyroid eye disease.

How can the Barret index be used to evaluate patients with thyroid eye disease?

The Barret index is a quantitative measure used to estimate the risk of compressive optic neuropathy in patients with thyroid eye disease by measuring the degree of apical crowding.

What is the significance of the 'Coca-Cola bottle' sign in thyroid eye disease?

The 'Coca-Cola bottle' sign refers to the appearance of the extraocular muscles in thyroid eye disease, where the muscle bellies are enlarged and the tendons are spared, resembling the shape of a Coca-Cola bottle.

What distinguishes orbital lymphoma from other pathologies on MRI?

Orbital lymphoma is distinguished by the presence of diffusion restriction on MRI, indicating a hypercellular tumor.