Neck Zones: Anatomic Classification and Clinical Relevance
The neck is divided into three anatomic zones—Zone I (clavicles/sternal notch to cricoid cartilage), Zone II (cricoid cartilage to mandibular angle), and Zone III (mandibular angle to skull base)—but modern management of penetrating neck trauma has shifted to a "no-zone" approach that prioritizes clinical signs over anatomic location. 1
Anatomic Boundaries of Neck Zones
The traditional zonal classification system divides the neck based on bony and cartilaginous landmarks:
Zone I (Thoracic Inlet): Extends from the clavicles and sternal notch superiorly to the cricoid cartilage, containing vital structures including major vessels (subclavian and innominate vessels, proximal carotid and vertebral arteries) and the thyroid gland, with surgical access being most challenging due to bony constraints of the thoracic inlet 1
Zone II (Mid-Neck): Extends from the cricoid cartilage inferiorly to the angle of the mandible superiorly, historically the most accessible zone for surgical exploration, containing critical structures like the carotid arteries, internal jugular veins, trachea, esophagus, and recurrent laryngeal nerves 1
Zone III (Superior Neck): Extends from the mandibular angle to the skull base, containing the distal carotid and vertebral arteries, with surgical access complicated by proximity to the skull base and mandible 1, 2
Evolution to "No-Zone" Management Approach
The American College of Radiology now recommends a selective approach based on clinical signs rather than anatomic zones alone for managing penetrating neck trauma. 1, 3
Why the Shift Away from Zone-Based Management?
CT angiography has revolutionized evaluation with sensitivity of 90-100% and specificity of 98.6-100% for detecting vascular injuries, enabling safe selective management regardless of the zone of injury 1, 4
The presence or absence of hard signs determines the need for immediate surgical exploration, not the zone of injury 1, 3
Zone-based algorithms led to increased reliance on invasive diagnostic modalities and higher rates of nontherapeutic neck exploration 5
Clinical Management Algorithm
Hard Signs Requiring Immediate Surgical Exploration (No Imaging)
Proceed directly to the operating room without imaging for any of the following 3, 4:
- Active hemorrhage or expanding hematoma
- Pulsatile hematoma
- Bruit or thrill over vessels
- Hemodynamic instability (hemorrhagic shock)
- Unilateral upper-extremity pulse deficit
- Airway compromise or air bubbling in the wound
- Hemoptysis (suggests tracheal or major vascular injury)
- Massive hematemesis
- Dysphonia (suggests laryngeal or recurrent laryngeal nerve injury)
- Pneumothorax
Delaying surgical exploration in patients with hard signs significantly increases mortality. 3, 4
Soft Signs Requiring Imaging Before Decision
For hemodynamically stable patients without hard signs, obtain CT angiography as first-line imaging 3, 4:
- Dysphagia (may indicate esophageal or pharyngeal injury)
- Nonpulsatile/nonexpanding hematoma
- Venous oozing
- Subcutaneous emphysema
CT angiography is the preferred imaging modality regardless of injury zone, with 90-100% sensitivity for vascular injuries and 100% sensitivity for aerodigestive injuries. 6, 4
Additional Imaging Considerations
Perform CT esophagography in conjunction with CT angiography for suspected digestive tract injuries, with sensitivity of 95-100% 4
Consider conventional arteriography only for equivocal CTA findings with vascular concerns 3
Historical Context: When Zones Still Matter
While the no-zone approach dominates modern management, anatomic zones retain relevance in specific contexts:
Zone I and III injuries historically required angiography due to difficult surgical access, with Zone III injuries sometimes managed by transcatheter embolization rather than exploration 2
Zone III arterial injuries may require specialized approaches including angiographic embolization or occipital craniectomy for vertebral artery injuries 2
Early subspecialty involvement (otolaryngology, vascular surgery, neurosurgery) is essential given complex anatomy, particularly in Zone I and III injuries 4
Common Pitfalls to Avoid
Do not delay surgical exploration for imaging in patients with hard signs—mortality increases significantly with delays 3, 4
Do not blindly clamp bleeding vessels in the neck—this can damage uninvolved structures, especially nerves 7
Do not rely on clinical assessment alone for Zone III injuries—angiography is essential as clinical examination may be misleading and injuries may go undetected 2
Do not assume all penetrating injuries deep to the platysma require exploration—selective management based on CT angiography findings reduces nontherapeutic explorations 5