Karuna Dewan1, Merry E Sebelik2, John D Boughter3, Courtney B Shires4. 1. Department of Otolaryngology, Head and Neck Surgery, University of Stanford, Stanford, CA, USA. 2. Department of Otolaryngology, Head and Neck Surgery, Emory University, Atlanta, GA, USA. 3. Department of Anatomy and Neurobiology, Head and Neck Surgery, University of Tennessee Health Science Center, Memphis, TN, USA. 4. Department of Otolaryngology, Head and Neck Surgery, University of Tennessee Health Science Center, Memphis, TN, USA.
Abstract
BACKGROUND: Post-thyroidectomy dysphonia can result from recurrent laryngeal nerve (RLN) injury. Confirmation of postoperative recurrent nerve function has prompted many surgeons to advocate laryngoscopic examination. Indirect and flexible laryngoscopy permit visualization of vocal cord motion, but not all thyroid surgeons are skilled in these techniques. Indirect laryngoscopy has a significant failure rate due to gag reflexes or anatomical obstruction. Flexible fiberoptic laryngoscopy, the current gold standard, allows reliable visualization of the cords, but perioperative examination is not always feasible for lack of equipment or training. Recent studies suggest vocal fold ultrasound as an alternative to flexible laryngoscopy. It offers the advantages of being non-invasive and painless without radiation exposure or sedation. Whereas ultrasound has been compared to laryngoscopy in the clinical setting, there remains a need for correlation of laryngeal ultrasound results with known neurophysiology in the normal and injured state. An animal model was proposed that reproduces neck surgery-associated recurrent nerve injury. The model allowed simultaneous recording of laryngeal endoscopy and transcutaneous high-resolution ultrasound during stimulation of intact and injured RLNs. METHODS: One RLN was injured in each of 4 rats. Rats were kept anesthetized during the fiberoptic examination and laryngeal ultrasound procedures. Following surgery and subsequent imaging the rats were given a lethal anesthetic dose. Results of both imaging modalities were compared to the presence or absence of neuromuscular action potential following stimulation of the recurrent nerve. RESULTS: The investigators observed a 100% correlation between endoscopic and ultrasonographic assessments. CONCLUSIONS: This study validated the clinical use of diagnostic ultrasound in vocal cord dysfunction in a rodent model.
BACKGROUND: Post-thyroidectomy dysphonia can result from recurrent laryngeal nerve (RLN) injury. Confirmation of postoperative recurrent nerve function has prompted many surgeons to advocate laryngoscopic examination. Indirect and flexible laryngoscopy permit visualization of vocal cord motion, but not all thyroid surgeons are skilled in these techniques. Indirect laryngoscopy has a significant failure rate due to gag reflexes or anatomical obstruction. Flexible fiberoptic laryngoscopy, the current gold standard, allows reliable visualization of the cords, but perioperative examination is not always feasible for lack of equipment or training. Recent studies suggest vocal fold ultrasound as an alternative to flexible laryngoscopy. It offers the advantages of being non-invasive and painless without radiation exposure or sedation. Whereas ultrasound has been compared to laryngoscopy in the clinical setting, there remains a need for correlation of laryngeal ultrasound results with known neurophysiology in the normal and injured state. An animal model was proposed that reproduces neck surgery-associated recurrent nerve injury. The model allowed simultaneous recording of laryngeal endoscopy and transcutaneous high-resolution ultrasound during stimulation of intact and injured RLNs. METHODS: One RLN was injured in each of 4 rats. Rats were kept anesthetized during the fiberoptic examination and laryngeal ultrasound procedures. Following surgery and subsequent imaging the rats were given a lethal anesthetic dose. Results of both imaging modalities were compared to the presence or absence of neuromuscular action potential following stimulation of the recurrent nerve. RESULTS: The investigators observed a 100% correlation between endoscopic and ultrasonographic assessments. CONCLUSIONS: This study validated the clinical use of diagnostic ultrasound in vocal cord dysfunction in a rodent model.
Authors: Belachew Tessema; Rick M Roark; Michael J Pitman; Philip Weissbrod; Sansar Sharma; Steven D Schaefer Journal: Laryngoscope Date: 2009-08 Impact factor: 3.325
Authors: Sujana S Chandrasekhar; Gregory W Randolph; Michael D Seidman; Richard M Rosenfeld; Peter Angelos; Julie Barkmeier-Kraemer; Michael S Benninger; Joel H Blumin; Gregory Dennis; John Hanks; Megan R Haymart; Richard T Kloos; Brenda Seals; Jerry M Schreibstein; Mack A Thomas; Carolyn Waddington; Barbara Warren; Peter J Robertson Journal: Otolaryngol Head Neck Surg Date: 2013-06 Impact factor: 3.497