Neck Roentgenogram-based Indices for Prediction of Difficult Laryngoscopy in Patients with Thyroid Swelling Undergoing Surgery – A Pilot Study

Introduction: Enlarged thyroid gland can alter the anatomy of the airway, and so, direct laryngoscopy can be difficult. The aim of the study was to find if neck X-ray could be a surrogate marker in the prediction of difficult laryngoscopy in thyroid swelling patients. Materials and Methods: This is a prospective, observational and cohort study including 50 patients undergoing elective thyroid surgery. The clinical bedside predictors studied were modified Mallampati grading, upper lip bite test (ULBT), thyromental distance (TMD), sternomental distance (SMD), degree of neck extension, inter-incisor gap, radiological variables mandibulohyoid distance (MHD), Angle A: between line passing through C2 and central incisor and line joining the tip of upper incisors with C6 vertebra, Angle B: between a vertical line passing through C6 and a horizontal line passing through the occlusal surface of maxillary teeth and compared with Cormack–Lehane grading. Results: We found TMD, SMD, modified Mallampati test, ULBT, MHD of >1.89 cm, Angle A >38° and Angle B <100° were significantly ( P < 0.05) associated with difficult laryngoscopy in patients with thyroid swelling. Conclusion: Hence, we conclude that MHD, extension Angle A and extension Angle B are useful adjuncts to the identification of a difficult airway – however, they are not useful as single pre-operative tests to identify difficult airways and will need to be considered along with routine pre-operative airway tests to rule out the possibility of a difficult airway.