Abstract
We read with interest the article by Dr. Lee and colleagues, entitled “Routine Preoperative Laryngoscopy for Thyroid Surgery Is Not Necessary Without Risk Factors” (1). We have concerns about the study design and the conclusions drawn. The study is described as a case–control design, but there are no appropriate controls, and the expected statistical analysis, an odds ratio for vocal cord paralysis (VCP) among the exposed compared with unexposed, is not reported. Furthermore, the authors provide no details on which patients were chosen for examination, how they were chosen, or who performed the laryngoscopies (consultant surgeon or junior doctors), nor do they assess voice with validated voice rating scales (2), so from this study it is not actually possible to establish with confidence the factors associated with a preoperative VCP.
In contrast to other studies, the authors report malignant cytology is not a risk factor for VCP. However, the volume of preoperatively identified malignant disease in this series is low (13.3%) and these results are thus not generalizable to thyroid practices with higher volumes of malignant disease. It is well established that patients with thyroid malignancy, especially those with posterior extrathyroidal extension or central compartment neck metastases, are at greater risk for recurrent laryngeal nerve invasion. This provides the rationale for preoperative laryngeal examination in such patients (3,4). As such, the suggestion by the authors that malignant cytology might not be an indication for laryngoscopy is, in our opinion, alarming and dangerous.
The authors propose that the risk of not preoperatively identifying a VCP, complete or incomplete, is mitigated by use of intraoperative nerve monitoring (IONM). However, vocal cord (fold) motion and electrical potentials are separate entities. Patients with incomplete VCPs commonly have electrical electromyogram (EMG) signal in the “normal” range and patients with complete VCPs can still exhibit EMG signal to direct nerve stimulation. Thus, IONM is clearly not a substitute for adequate preoperative vocal cord assessment.
The authors provide scant detail on how the cost estimate of 400AUD per laryngoscopy was derived. Given the Medicare Benefits Schedule for laryngoscopy and initial consultation in Australia is approximately one half this amount, this figure seems excessive. An absolute value of cost savings for a multiyear cohort is reported, with no reference to the total cost of care for these patients. To make a more meaningful analysis, the cost of laryngoscopy should be compared with the costs of preventable complications related to unidentified preoperative deficits.
Preoperative VCP in this data set, as in others, is uncommon. However, the risk of postoperative VCP in recent series is 5–8%. The finding of postoperative VCP inevitably raises questions as to the causation—iatrogenic versus pre-existing—and the necessity to perform preoperative laryngoscopy are thus driven as much by postoperative complication rate as it is by preoperative incidence.
Overall, the value of preoperative laryngeal examination is well established and embedded in recent guidelines of the American Academy of Otolaryngology Head and Neck Surgery and the American Thyroid Association (2 –4). Sincerely.