FRCS (ORL-HNS) Section 1 Question of the Day

FRCS (ORL-HNS) Question of the Day

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Category: FRCS (ORL-HNS) - Anatomy

A 52-year-old male construction worker presents to the emergency department following a fall from scaffolding. He exhibits periorbital ecchymosis, limited ocular motility, and blurred vision in his right eye. A CT scan reveals a complex orbital fracture involving multiple orbital walls. During surgical planning, precise anatomical knowledge is essential to avoid neurovascular complications. Which of the following statements regarding the intricate anatomy of the orbit is correct?

The optic canal is located in the orbital roof and transmits the oculomotor nerve (CN III) and the abducent nerve (CN VI).

The superior orbital fissure transmits the trochlear nerve (CN IV), the ophthalmic division of the trigeminal nerve (V1), and the abducent nerve (CN VI).

The inferior orbital fissure is bordered superiorly by the lateral palpebral ligament and transmits the maxillary division of the trigeminal nerve (V2).

The annular ligament of Zinn encircles the optic nerve and provides attachment for the extraocular muscles.

The ethmoidal arteries run through the superior orbital fissure alongside the oculomotor nerve.

Correct Answer: b. The superior orbital fissure transmits the trochlear nerve (CN IV), the ophthalmic division of the trigeminal nerve (V1), and the abducent nerve (CN VI).

Explanation:
Understanding the detailed anatomy of the orbit is critical, especially in the context of complex fractures that may compromise neurovascular structures. Here's a breakdown of each option:

Option a: Incorrect. The optic canal is indeed located in the orbital roof; however, it transmits the optic nerve (CN II) and the ophthalmic artery, not the oculomotor nerve (CN III) or the abducent nerve (CN VI). The oculomotor and abducent nerves pass through the superior orbital fissure.
Option b: Correct. The superior orbital fissure is a key anatomical feature located between the greater and lesser wings of the sphenoid bone. It transmits several important structures, including:
- The trochlear nerve (CN IV)
- The ophthalmic division of the trigeminal nerve (V1)
- The abducent nerve (CN VI)
- The oculomotor nerve (CN III) also passes through here
- Superior ophthalmic vein This makes option (b) the correct statement.
Option c: Incorrect. The inferior orbital fissure is bordered superiorly by the maxilla and the inferior orbital margin, not the lateral palpebral ligament. It transmits the infraorbital nerve (a branch of V2), the infraorbital vessels, and the zygomatic nerve. The maxillary division (V2) does pass through, but the description of the borders is incorrect.
Option d: Incorrect. The annular ligament of Zinn, also known as the common tendinous ring, encircles the optic nerve and serves as the origin for the four rectus muscles (superior, inferior, medial, and lateral) but not the oblique muscles. It does not provide attachment for all extraocular muscles, specifically excluding the obliques.
Option e: Incorrect. The ethmoidal arteries (anterior and posterior) run through the superior orbital fissure but alongside the ophthalmic division of the trigeminal nerve (V1), not specifically alongside the oculomotor nerve (CN III). Moreover, the main structures associated with the superior orbital fissure are the cranial nerves III, IV, V1, VI, and the superior ophthalmic vein.

Further Reading:

StatPearls. Anatomy, Head and Neck, Orbit Bones [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jul 24 [cited 2024 Dec 7]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK531490/
TeachMeAnatomy. The Bony Orbit - Borders - Contents - Fractures [Internet]. [cited 2024 Dec 7]. Available from: https://teachmeanatomy.info/head/organs/eye/bony-orbit/
SpringerLink. Orbital Fractures [Internet]. In: Management of Orbital Trauma. Singapore: Springer; [cited 2024 Dec 7]. Available from: https://link.springer.com/chapter/10.1007/978-981-15-1346-6_57

Additional Concepts:

Neurovascular Structures in the Orbit: Detailed knowledge of the pathways of cranial nerves and blood vessels within the orbit is essential to prevent inadvertent damage during surgical interventions or to understand clinical presentations following trauma.
Orbital Apex Syndrome: Injury or fractures affecting the superior orbital fissure and optic canal can lead to orbital apex syndrome, characterized by multiple cranial nerve deficits and potential vision loss.
Surgical Approaches to the Orbit: Familiarity with the anatomical landmarks such as the superior and inferior orbital fissures, optic canal, and annular ligament of Zinn aids surgeons in selecting appropriate approaches for accessing different orbital compartments while minimizing risks.
Imaging Interpretation: Proficiency in interpreting orbital CT scans and MRI is crucial for identifying the extent of fractures, herniation of orbital contents, and involvement of neurovascular structures, guiding both conservative and surgical management.
Cranial Nerve Pathways: Understanding the course of cranial nerves III, IV, V1, V2, and VI within the orbit helps in correlating clinical symptoms with potential sites of injury, enhancing diagnostic accuracy and treatment planning.

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