Modified Radical Neck Dissection: Preserved Structures
The correct answer is B, C, and D—modified radical neck dissection (MRND) preserves the sternocleidomastoid muscle, spinal accessory nerve, and internal jugular vein, while removing all lymph node levels (I-V) that would be included in a classic radical neck dissection. 1, 2
Key Defining Features of MRND
MRND is classified as a "comprehensive" neck dissection that removes all lymph node groups from levels I-V while preserving one or more of the following nonlymphatic structures: sternocleidomastoid muscle, internal jugular vein, or spinal accessory nerve. 1, 2
- The preservation of these structures distinguishes MRND from radical neck dissection, which sacrifices all three structures 1
- Contemporary nomenclature prefers "comprehensive" versus "selective" classification rather than the older "modified radical" terminology, though MRND remains widely recognized 1, 2
Structure-Specific Preservation
Spinal Accessory Nerve (Cranial Nerve XI)
- Preservation of the spinal accessory nerve is the hallmark modification that significantly reduces postoperative shoulder dysfunction 3
- Postoperative morbidity rates are 25% for MRND with nerve preservation versus 46.7% for radical neck dissection with nerve sacrifice 3
- The nerve is most safely identified at Erb's point where it exits the posterior border of the sternocleidomastoid muscle, approximately 0.90 cm from the greater auricular point 3
- Cable grafting with great auricular nerve can be performed if the spinal accessory nerve must be sacrificed, resulting in intermediate functional outcomes between radical and modified dissections 4
Sternocleidomastoid Muscle and Internal Jugular Vein
- Both structures are routinely preserved in MRND unless directly invaded by tumor 1, 2
- Preservation of the internal jugular vein is particularly important when bilateral neck dissections are required to maintain adequate venous drainage 5
What Is NOT Preserved
The submandibular salivary gland (option D) is typically removed during MRND when level I lymph nodes are dissected, as it lies within the level IB nodal basin. 2, 5
- Level I dissection is essential for oral cavity tumors with nodal involvement and includes removal of submental (IA) and submandibular (IB) nodes 2
- The submandibular gland is removed en bloc with level IB nodes to ensure adequate oncologic clearance 2
Clinical Application
- MRND is indicated for N1-N2 disease with clinically evident nodal metastases and manageable tumor burden 2
- For N3 disease, comprehensive neck dissection (which may be MRND or radical depending on tumor involvement) is recommended 1, 2
- A properly performed MRND should yield 10 or more lymph nodes for pathologic examination 2, 5
Common Pitfall
Do not confuse MRND with selective neck dissection—selective dissections remove three or fewer nodal levels and are appropriate for N0 disease, while MRND removes all five levels (I-V) and is used for therapeutic management of clinically positive nodes. 1, 2, 5