Quantification of rat supraglottic laryngeal sensation threshold.

OBJECTIVE: Laryngeal adductor response (LAR) to air puff is used as a reliable method in evaluating sensation thresholds (ST) in human laryngeal sensory disorders. This method has been difficult to perform in small subjects such as rodents. The aims of this study were to 1) evaluate ST to air puff under binocular microlaryngoscopy in rats to evaluate laryngeal sensory disorders, 2) determine sensory thresholds at varying target locations, and 3) determine the ideal depth of anesthesia. STUDY DESIGN: Animal study. METHODS: Rats were induced with ketamine/xylazine. The level of anesthesia was monitored by spontaneous glottic closure and corneal reflex testing. Air puffs were delivered to the epiglottis, arytenoid, and piriform sinus at varied pressures with pulse time kept constant. Sensation thresholds were determined by direct visualization of the larynx using a binocular microscope. Topical lidocaine was then applied to the larynx and ST was determined. Trials were repeated in a small subset of animals. RESULTS: Twenty-six trials were performed in 14 rats. Mean STs were 39 ± 9.7 mm Hg at the epiglottis, 48.8 ± 10.5 at the arytenoid, and not detectable at the pyriform sinus. Repeated trials demonstrated consistent results. Lidocaine effectively ablated the LAR in each trial. The LAR was difficult to induce while corneal reflex was absent and was difficult to distinguish from spontaneous glottic closures while under lighter sedation. CONCLUSION: Air pulse stimulation in rats is a simple, reliable, and effective way to determine laryngopharyngeal STs in rats and can be used as an efficient and affordable method for experimentation involving laryngeal sensory disorders. LEVEL OF EVIDENCE: NA. Laryngoscope, 127:E265-E269, 2017.

Compound motor action potential duration and latency are markers of recurrent laryngeal nerve injury.

OBJECTIVE: Compound motor action potential (CMAP) can quantitatively evaluate innervation following injury to the recurrent laryngeal nerve (RLN) in canines. CMAP duration (the total time of CMAP) and latency (the time between the nerve impulse and the onset of action potentials) have not been assessed following RLN injury. STUDY DESIGN: Animal study. METHODS: Twelve canine hemilaryngeal preparations were investigated. Baseline CMAP duration and latency were derived. Group A (n = 5) underwent RLN stretch injury, and group B (n = 7) underwent RLN transection/repair. The change in CMAP duration and latency was assessed between the baseline and 6-month measurements using receiver operator characteristic (ROC) curves for each group individually and combined. RESULTS: Six months following injury, transection/repair injuries had the most significant increase in CMAP duration (2.8 ± 0.6 ms vs. 4.2 ± 0.8 ms, difference 1.4 ms 95% confidence interval [CI]: 0.43 to 2.40) and latency (2.6 ± 0.5 ms vs. 5.6 ± 1.5 ms, difference 3.0 ms 95% CI: 1.65 to 4.38). Stretch injuries also caused an increase in CMAP duration (2.3 ± 0.8 ms vs. 3.0 ± 0.6 ms, difference 0.7 ms 95% CI: -0.49 to 1.77) and latency (2.5 ± 0.8 ms vs. 4.7 ± 1.5 ms, difference 2.3 95% CI: 0.76 to 3.80). Using ROC curves, CMAP duration and latency differentiated between the baseline control and RLN injury at 6 months (area under the curve = 0.78 and 0.98, respectively). CONCLUSION: CMAP duration and latency are both quantitative measures that may have clinical utility as markers of RLN injury. CMAP latency had superior discrimination between injured and uninjured RLNs. Increased CMAP duration and latency may be explained by incomplete myelination and focal conduction block. LEVEL OF EVIDENCE: NA. Laryngoscope, 127:1855-1860, 2017.

Potassium titanyl phosphate laser welding following complete nerve transection.

OBJECTIVES/HYPOTHESIS: Cranial nerve transection during head and neck surgery is conventionally repaired by microsuture reanastomosis. Laser nerve welding (LNW), using CO2 laser to spot-weld the epineurium of transected nerve endings, has been shown in animal models to be a novel alternative to microsuture repair. This method avoids needle/suture material and minimizes instrumentation of the nerve. We hypothesized that potassium titanyl phosphate (KTP) laser would be superior to CO2 laser in repairing transected nerves. Using a rat posterior tibial nerve injury model, we compared CO2 laser, KTP laser, and microsuture reanastomosis. STUDY DESIGN: Animal study. METHODS: Animals underwent unilateral posterior tibial nerve transection. The injury was repaired by microsuture repair (n = 15), CO2 laser repair (n = 15), or KTP laser repair (n = 15). Weekly walking tracks were performed to measure functional recovery. Nerve segments were harvested for axon counting. RESULTS: At 6 weeks, the KTP LNW had the best functional recovery (92.4 ± 8.6%) compared to microsuture repair (84.5 ± 10.2%, difference 7.9%, 95% confidence interval [CI]: 0.84%-14.96%). CO2 laser repair had a functional recovery of 86.8 ± 11.2%. KTP LNW had better axon recovery compared to transection/repair (difference 530.7 axons, 95% CI: 329.9-731.5). Operative time for the microsuture repair was 18.2 ± 6.8 minutes, compared to 5.8 ± 3.7 minutes for the LNW groups (difference 12.4 minutes, 95% CI: 8.6-16.2 minutes). CONCLUSIONS: KTP, CO2 , and microsuture repair all showed good functional recovery following complete transection of the posterior tibial nerve. Following complete nerve transection during head and neck surgery, KTP LNW may be a novel alternative to microsuture repair. LEVEL OF EVIDENCE: NA Laryngoscope, 127:1525-1530, 2017.

Assessment of otolaryngic knowledge in primary care residents.

OBJECTIVES: (1) Determine the amount of exposure to otolaryngology in medical training of non-otolaryngology residents. (2) Evaluate the general otolaryngic knowledge in these residents. STUDY DESIGN: Cross-sectional survey. SETTING: Academic medical center. SUBJECTS AND METHODS: A 10-question multiple-choice quiz was given to residents in family practice, pediatrics, emergency medicine, and internal medicine during scheduled educational conferences. Residents were also asked if they ever participated in an otolaryngology rotation during medical school or residency. Medical students and otolaryngology residents completed the quiz to act as controls. RESULTS: A total of 98 examinations were analyzed (49 non-otolaryngology residents, 10 otolaryngology residents, and 39 second-year medical students). Only 24% of the non- otolaryngology residents had an otolaryngology rotation during medical school. The same amount (24%) had a rotation during residency. The average percentage correct on the quiz was 48%, 56%, and 92% for medical students, non-otolaryngology, and otolaryngology residents, respectively (P < 0.05). Questions with surprising results included one with an endoscopic image of the middle turbinate and examinees asked to identify the structure (non-otolaryngology residents = 18% correct). A laryngectomy stoma was shown and participants asked what would happen if the stoma was occluded for 10 minutes (non-otolaryngology residents = 20% correct). CONCLUSION: In this sample of non-otolaryngology residents, a minority experienced a clinical rotation in otolaryngology during medical school or residency. This nonvalidated questionnaire also suggested significant deficiencies in basic otolaryngic knowledge in these residents. Identifying mechanisms to improve exposure to otolaryngology in the medical training curriculum is needed.