Modified Radical Neck Dissection: Preserved Structures
The correct answers are A (Internal jugular vein), B (Sternomastoid muscle), and C (Spinal accessory nerve) – all three structures are preserved in a modified radical neck dissection, distinguishing it from a radical neck dissection. 1, 2
Definition and Key Structural Preservation
Modified radical neck dissection (MRND) is defined as a comprehensive neck dissection that removes all lymph node levels (I-V) while preserving one or more of the following nonlymphatic structures 1, 2:
- Sternocleidomastoid muscle 1, 2
- Internal jugular vein 1, 2
- Spinal accessory nerve (cranial nerve XI) 1, 2
The preservation of these structures does not affect whether the dissection is classified as "comprehensive" – the key distinction is that all nodal levels are removed while sparing these critical anatomic structures 1.
Structures NOT Preserved
Submandibular Salivary Gland (Option D)
- The submandibular gland is located within Level I of the neck dissection 1
- When Level I is included in a comprehensive neck dissection (which MRND is), the submandibular gland is typically removed as part of the nodal clearance 1, 3
Posterior Belly of Digastric Muscle (Option E)
- This muscle serves as an anatomic boundary for Level I dissection 1
- It is not a structure that defines the difference between radical and modified radical neck dissection 1
Clinical Significance of Nerve Preservation
Spinal accessory nerve preservation is particularly critical because it prevents the debilitating "shoulder syndrome" that occurs with nerve sacrifice 4:
- Postoperative shoulder morbidity occurs in 46.7% of radical neck dissections (with nerve sacrifice) compared to only 25% in modified neck dissections (with nerve preservation) 4
- The nerve should be identified at Erb's point where it exits the posterior border of the sternocleidomastoid muscle, approximately 0.90 cm from the greater auricular point 4
- Even when the nerve is preserved, careful surgical technique is essential as traumatic handling can still result in functional impairment 5
Contemporary Nomenclature Note
Modern guidelines prefer the terms "comprehensive" versus "selective" neck dissection rather than "radical" versus "modified radical," though MRND remains understood as a comprehensive dissection with preservation of the sternocleidomastoid muscle, internal jugular vein, and/or spinal accessory nerve 1, 3.