Surface-Based Localization of the Spinal Accessory Nerve in the Posterior Triangle: A High-Volume Cadaveric Study...

Area of Science:

• Anatomy
• Surgical Navigation

Background:

• The spinal accessory nerve (SAN) is vulnerable to injury during head and neck surgeries, particularly in the posterior cervical triangle.
• Current methods for surface-based SAN localization are insufficient for aesthetic and limited-access procedures.

Purpose of the Study:

• To establish reliable surface-based anatomical landmarks for spinal accessory nerve localization.
• To define a reproducible "danger zone" to enhance surgical safety in the posterior cervical triangle.

Main Methods:

• A cadaveric study involving 186 hemi-necks from 111 Thiel-embalmed cadavers.
• Measurement of distances between the SAN emergence point and four skeletal landmarks: mastoid process, sternoclavicular joint, midclavicular point, and acromioclavicular joint.
• Mathematical definition of a "danger zone" based on anatomical relationships and standard deviations.

Main Results:

• The spinal accessory nerve was consistently identified in all dissections.
• Mean distances from the nerve to landmarks: mastoid process (5.1 cm), sternoclavicular joint (11.0 cm), midclavicular point (9.1 cm), and acromioclavicular joint (12.8 cm).
• A circular danger zone with a mean diameter of 2.96 cm (6.9 cm² area) was calculated; a refined zone of 1.98 cm diameter (3.1 cm²) was defined using the mastoid process.

Conclusions:

• A clinically relevant and reproducible surface-based danger zone for SAN localization in the posterior cervical triangle has been defined.
• This model, anchored to palpable skeletal landmarks and validated on a large dataset, improves surgical safety.
• The proposed method facilitates preemptive nerve identification, crucial for oncologic and aesthetic neck procedures.