MRI Orbit – Anatomy | Pathology | Why Do It?

 

🧠 MRI Orbit – Anatomy | Pathology | Why Do It?

Anatomy of the Orbit

The orbit is the bony socket in the skull that houses and protects the eye and its associated structures.

✅ Key Orbital Structures:

1. Eyeball (Globe) – Retina, lens, cornea, sclera.

2. Optic Nerve (CN II) – Transmits visual information to the brain.

3. Extraocular Muscles – Move the eye (6 muscles).

4. Lacrimal Gland – Produces tears.

5. Blood Vessels – Ophthalmic artery, superior & inferior ophthalmic veins.

6. Nerves – Oculomotor (III), Trochlear (IV), Abducens (VI), and Trigeminal branches.

7. Fat – Cushions and supports the globe and muscles.

Common Orbital Pathologies on MRI

👁️‍🗨️ Inflammatory

• Orbital cellulitis

• Thyroid Eye Disease (Graves' orbitopathy)

• Idiopathic orbital inflammatory disease (orbital pseudotumor)

🧠 Neoplastic (Tumors)

• Optic nerve glioma

• Meningioma

• Lymphoma

• Retinoblastoma (in children)

• Metastases

🦠 Infective

• Orbital abscess

• Sinus-origin infections spreading into the orbit

mri orbit anatomy and pathology

🧨 Trauma

• Orbital fractures (blow-out fractures)

• Hematomas

• Foreign bodies

🧬 Congenital/Developmental

• Dermoid/epidermoid cysts

• Coloboma

• Orbital encephalocele

❓ Why Do MRI Orbit? – Indications

✅ MRI is preferred because:

• No radiation (safer, especially in pediatrics).

• Excellent soft tissue contrast for muscles, nerves, and tumors.

• Multiplanar capability.

📋 Common Clinical Indications:

1. Visual Loss / Optic Neuritis

2. Proptosis (bulging eye)

3. Orbital Mass Evaluation

4. Thyroid Eye Disease Assessment

5. Trauma with unclear CT findings

6. Ophthalmoplegia (limited eye movement)

7. Pre-surgical planning for tumors or decompression

MRI Orbit Protocol – Basic Sequences

• Axial & coronal T1W and T2W

• Fat-suppressed sequences

• Post-contrast T1W with fat suppression

• STIR for edema/inflammation

• DWI for tumor/infection by