Published in:
01-10-2014
Postoperative Vocal Cord Dysfunction Despite Normal Intraoperative Neuromonitoring: An Unexpected Complication With the Risk of Bilateral Palsy
Published in: World Journal of Surgery | Issue 10/2014
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Background
Intraoperative neuromonitoring (IONM) has become standard practice in thyroid surgery for many surgeons. It reduces the risk of vocal cord palsy in high-risk patients and has led to two-stage operations to prevent bilateral palsies. The specificity of detecting nerve injuries is not 100 %, leading to patients with vocal cord dysfunction (VCD) despite regular neuromonitoring (false-negative IONM). We aimed to evaluate possible risk factors for this phenomenon and its importance regarding bilateral palsies.
Methods
We performed a retrospective analysis of all patients with false-negative IONM.
Results
A total of 2152 patients (3426 nerves at risk) underwent surgery for benign disease between January 2008 and October 2010. Sensitivity for predicting VCD was 85.4 % and specificity 99.0 %. The positive predictive value was 68.0 % and the negative predictive value 99.6 %. We were not able to identify risk factors for false-negative IONM. We found four patients with delayed occurrence of VCD after regular IONM (1–8 weeks). We registered two patients with bilateral VCD after false negative IONM on the first side of bilateral resections (2/7) and four patients with bilateral palsy after correct IONM (4/1256). The relative risk for bilateral VCD between patients with false-negative IONM on the primary resection side and patients with correct IONM was 89.7.
Conclusions
Although seldom, false-negative IONM is of clinical importance as it bears a high risk of bilateral VCD if it occurs on the first side of a bilateral resection. It can also have a latent occurrence after surgery.