Selective recurrent laryngeal nerve stimulation using a penetrating electrode array in the feline model.

OBJECTIVES/HYPOTHESIS: Laryngeal muscles (LMs) are controlled by the recurrent laryngeal nerve (RLN), injury of which can result in vocal fold (VF) paralysis (VFP). We aimed to introduce a bioelectric approach to selective stimulation of LMs and graded muscle contraction responses. STUDY DESIGN: Acute experiments in cats. METHODS: The study included six anesthetized cats. In four cats, a multichannel penetrating microelectrode array (MEA) was placed into an uninjured RLN. For RLN injury experiments, one cat received a standardized hemostat-crush injury, and one cat received a transection-reapproximation injury 4 months prior to testing. In each experiment, three LMs (thyroarytenoid, posterior cricoarytenoid, and cricothyroid muscles) were monitored with an electromyographic (EMG) nerve integrity monitoring system. Electrical current pulses were delivered to each stimulating channel individually. Elicited EMG voltage outputs were recorded for each muscle. Direct videolaryngoscopy was performed for visualization of VF movement. RESULTS: Stimulation through individual channels led to selective activation of restricted nerve populations, resulting in selective contraction of individual LMs. Increasing current levels resulted in rising EMG voltage responses. Typically, activation of individual muscles was successfully achieved via single placement of the MEA by selection of appropriate stimulation channels. VF abduction was predominantly observed on videolaryngoscopy. Nerve histology confirmed injury in cases of RLN crush and transection experiments. CONCLUSIONS: We demonstrated the ability of a penetrating MEA to selectively stimulate restricted fiber populations within the feline RLN and selectively elicit contractions of discrete LMs in both acute and injury-model experiments, suggesting a potential role for intraneural MEA implantation in VFP management. LEVEL OF EVIDENCE: NA. Laryngoscope, 128:1606-1614, 2018.

Is Nebulized Lidocaine Adequate Topical Anesthesia for Diagnostic Transnasal Tracheoscopy?

OBJECTIVES: To evaluate if nebulized 4% lidocaine alone provides adequate laryngopharyngeal anesthesia for office-based diagnostic transnasal tracheoscopy (TNT). METHODS: A retrospective chart review (January 2011 to June 2014) and a prospective case series (July 2014 to December 2014) of patients who underwent diagnostic TNT were performed at a university voice and swallowing center. TNT cases were categorized by method of topical laryngopharyngeal anesthesia: nebulized 4% lidocaine and 4% lidocaine drip (phase I) and nebulized 4% lidocaine only (phase II). RESULTS: TNT was performed a total of 59 times on 38 patients. Eleven (69%) of 16 phase I TNT procedures involved significant patient discomfort and severe cough following the lidocaine drip. Forty-two (98%) of 43 phase II TNT procedures were completed comfortably; 1 case required additional anesthesia by lidocaine drip. Retrospectively, 100% (n=8) of patients who underwent both phase I and phase II TNTs were noted to prefer anesthesia with nebulizer alone. In a prospective case series of 14 phase II TNT cases, 6 (86%) of 7 patients who previously underwent phase I TNT reported preference for anesthesia with nebulizer alone. CONCLUSIONS: Nebulized lidocaine appears to provide sufficient laryngopharyngeal anesthesia for diagnostic TNT. It is preferred by patients over laryngeal drip.

Transnasal tracheoscopy.

OBJECTIVES/HYPOTHESIS: Unsedated transnasal tracheoscopy (TNT) has emerged as a technique in otolaryngology-head and neck surgery for an awake airway examination in the office setting. This study investigates the safety, procedural success rate, indications, and findings of TNTs performed over a 3-year period at an academic medical center. STUDY DESIGN: Retrospective chart review. METHODS: After institutional review board approval, billing records were reviewed for patients who underwent TNT from 2007-2009 in the University of Wisconsin-Madison Department of Otolaryngology-Head and Neck Surgery. Hospital charts for these patients were obtained, and data regarding patient demographics, complications, procedural success rate, indications, and findings were recorded. RESULTS: Sixty-eight TNTs were performed on 44 patients over the last 3 years (25 males, 19 females; age range, 16-91 years). No complications were noted. Ninety-one percent of procedures were able to be completed. Indications for TNT were to: 1) detect airway stenosis or pathology, 2) evaluate the larynx and trachea prior to airway surgery, 3) monitor postoperative results of airway interventions, and 4) evaluate the airway prior to tracheotomy tube decannulation. CONCLUSIONS: TNT is a safe procedure that can be performed on the unsedated patient using only topical anesthesia and is an attractive alternative to rigid bronchoscopy. The procedural success rate was high, indicating good patient tolerance. The indications for TNT, including its use as a tool for surgical planning, have become better defined. TNT has become a standard tool in the management of patients with airway pathology in our practices.