Selective laryngoscopy before thyroidectomy: a risk assessment

Patients presenting for thyroidectomy may have an unrecognized pre-existing vocal cord palsy (VCP). This raises the danger of bilateral VCP if a patient sustains an injury to the RLN on the sole functioning side. Part of the rationale for routine preoperative laryngoscopy is to eliminate such a risk. This paper endeavours to quantify the relevant potential risk.

Patients who underwent laryngoscopy prior to thyroid or parathyroid surgery in an endocrine surgical unit over a 5 year period were identified. Literature review revealed four papers in which VCP prevalence in patients without risk factors was reported. Using our data, combined with that of these other authors, the background rate of pre-existing VCP was ascertained, and the subsequent risk of bilateral VCP estimated.

Of our 632 patients who underwent preoperative laryngoscopy, there were four patients (0.63%) who were found to have a unilateral VCP, but all had voice symptoms or previous neck surgery. When patients with these risk factors are excluded, our data combined with the published data provides a pre-existing VCP rate of 0.2%. Calculations estimate that if preoperative laryngoscopy is omitted in patients with no risk factors, the risk of bilateral VCP, due to the nerve on the sole functioning side being injured, would be between 1/50000 and 1/150000, depending on an individual surgeon's level of experience.

Selective use of laryngoscopy prior to thyroidectomy would result in an acceptably low statistical risk of bilateral VCP. Routine laryngoscopy for all patients is not necessary.