What are the Donaldson criteria for assessing nerve supply?

Donaldson Criteria for Nerve Supply Assessment

The Donaldson criteria for assessing nerve supply focus on evaluating facial nerve preservation versus resection during salivary gland malignancy surgery, with specific indicators for when to preserve or sacrifice nerve branches based on preoperative function and intraoperative findings. 1

Key Criteria for Nerve Assessment

• Facial nerve preservation is strongly recommended in patients with intact preoperative facial nerve function when a dissection plane can be created between the tumor and the nerve 1
• Resection of involved facial nerve branches is recommended when patients have preoperative facial nerve weakness or when branches are found to be encased or grossly involved by confirmed malignancy 1
• Nerve enhancement, nerve enlargement, foraminal expansion, and muscle volume loss are key imaging findings that suggest perineural tumor invasion 1

Imaging Modalities for Nerve Assessment

• MRI is the preferred imaging method for evaluating perineural spread of tumor, with contrast-enhanced sequences being essential 1
• Thin-section MRI with high spatial resolution is required to directly visualize the cranial nerves 1, 2
• CT provides complementary information on the integrity of bony structures and foramina when evaluating nerve pathways 1
• For comprehensive evaluation, imaging should include the entire course of the affected nerve from its nucleus to the end organ 2

Clinical Evaluation Components

• Preoperative assessment of facial nerve function is critical in determining the surgical approach 1
• Electromyography can be used to confirm nerve weakness believed to be related to tumor involvement 1
• Intraoperative assessment includes identifying whether a dissection plane can be created between tumor and nerve 1
• Asymmetry of facial musculature may indicate perineural tumor spread along the facial nerve 1

Decision Algorithm for Nerve Management

1. Assess preoperative nerve function clinically and with electromyography if indicated 1
2. Obtain high-resolution contrast-enhanced MRI to evaluate nerve anatomy and potential tumor involvement 1
3. During surgery, attempt to identify a dissection plane between tumor and nerve 1
4. Preserve nerve if:
   • Preoperative function is intact AND
   • A dissection plane can be created between tumor and nerve 1
5. Resect nerve branches if:
   • Preoperative facial weakness is present OR
   • Branches are encased/grossly involved by confirmed malignancy 1

Pitfalls and Considerations

• Perineural spread of tumor along the facial nerve may evade even meticulous imaging, requiring careful clinical correlation 1
• In early-stage low- and intermediate-grade parotid cancers, complete surgical resection with close margins can result in excellent disease control while preserving facial nerve function 1
• For advanced and high-grade tumors, the decision to sacrifice nerve branches becomes more complex and must balance oncologic control with functional preservation 1
• Adjuvant radiation therapy may be considered when nerve preservation is chosen in higher-risk cases 1

Advanced Imaging Techniques

• 3.0T MRI is preferred over 1.5T due to superior signal-to-noise ratios and spatial resolution 2
• Thin-cut heavily T2-weighted contrast-enhanced modified balanced SSFP sequences provide detailed imaging of nerves 2
• High-resolution 3D T2-weighted imaging, MRA, and 3D T1-weighted contrast-enhanced sequences can assess for neurovascular compression 2