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Persistent Shoulder Dysfunction After Spinal Accessory Nerve-Preserving Neck Dissection: A Prospective Functional and
Borja A Bazán Inostroza1, Jorge Prada Pendolero2, Gustavo Eisenberg Plaza3
1Department of ENT and Skull Base Surgery, Hospital Universitario de La Princesa, Madrid, Spain; Department of Medicine, Universidad Autónoma de Madrid, Madrid, Spain.
Objectives:
To characterize spinal accessory nerve (SAN) related shoulder dysfunction under standardized, controlled conditions following anatomically nerve-preserving bilateral selective neck dissection, integrating objective functional, electromyographic, and patient-reported outcomes.
Design:
Prospective cohort study.
Setting:
Single tertiary referral centre, [blinded institution], Spain.
Participants:
Twenty-six patients with head and neck squamous cell carcinoma requiring bilateral selective neck dissection of levels II-IV including level IIB.
Main Outcome Measures:
Shoulder range of motion (ROM) by digital inclinometry, electromyography (EMG) amplitude and latency of the trapezius muscle, muscle strength (British Medical Research Council scale), shoulder girdle examination, and patient-reported outcomes (Neck and Shoulder Disability Index), assessed preoperatively and at 1, 3, and 6 months postoperatively. Intraoperative neuromonitoring with compound muscle action potential recording was performed before and after dissection.
Results:
Despite stable intraoperative neuromonitoring amplitudes, significant reductions in abduction (mean 30.5 °, p = 0.0003) and flexion ROM (mean 23.8°, p = 0.0008) persisted at 6 months. EMG amplitude decreased from 8.85 to 4.47 mV at 1 month (p = 0.0003), with partial recovery at 6 months. Latency increased transiently. Strength deficits (BMRC ≤4/5) were present in 19.2% of patients at 6 months. Neck Disability Index increased significantly (p = 0.004).
Conclusion:
Spinal accessory nerve dysfunction can occur despite anatomical preservation and stable intraoperative monitoring, suggesting neurapraxic changes arising from mechanisms not captured in real time such as possibly traction or perineural disruption at level IIB. These findings highlight the importance of postoperative surveillance and early targeted rehabilitation.
