A Mouse Model of Dysphagia After Facial Nerve Injury

Abstract

Objective Dysphagia is common following facial nerve injury; however, research is sparse regarding swallowing‐related outcomes and targeted treatments. Previous animal studies have used eye blink and vibrissae movement as measures of facial nerve impairment and recovery. The purpose of this study was to create a mouse model of facial nerve injury that results in dysphagia to enhance translational research outcomes. Study design Prospective animal study. Methods Twenty C57BL/6J mice underwent surgical transection of the main trunk (MT) (n = 10) or marginal mandibular branch (MMB) (n = 10) of the left facial nerve. Videofluoroscopic swallow study (VFSS) assays for drinking and eating were performed at baseline and 14 days postsurgery to quantify several deglutition‐related outcome measures. Results VFSS analysis revealed that MT transection resulted in significantly slower lick and swallow rates during drinking (P ≤ .05) and significantly slower swallow rates and longer inter‐swallow intervals during eating (P ≤ .05), congruent with oral and pharyngeal dysphagia. After MMB transection, these same VFSS metrics were not statistically significant (P > .05). Conclusion The main finding of this study was that transection of the facial nerve MT leads to oral and pharyngeal stage dysphagia in mice; MMB transection does not. These results from mice provide novel insight into specific VFSS metrics that may be used to characterize dysphagia in humans following facial nerve injury. We are currently using this surgical mouse model to explore promising treatment modalities such as electrical stimulation to hasten recovery and improve outcomes following various iatrogenic and idiopathic conditions affecting the facial nerve. Level of Evidence NA Laryngoscope, 131:17–24, 2021

Experimental Injury Rodent Models for Oropharyngeal Dysphagia

“…The evidence of tongue bite was also observed [ 14 ]. There was the mouse model of oropharyngeal dysphagia with facial nerve injury [ 15 ]. Dysphagia was caused by sectioning the main trunk of the facial nerves of 6 to 12-months-old male and female mice.…”

“…Any damage to them causes paralysis and renders the tongue and facial muscles incapable of functioning properly. Injury to the hypoglossal or facial nerve can occur because of infection, drug toxicity, tumor compression, trauma, and iatrogenic or unknown causes [ 15 , 26 , 27 ]. Injury to the hypoglossal or facial nerve is one of the most commonly observed cranial nerve injuries [ 26 , 27 ].…”

“…A mouse model of oropharyngeal dysphagia was developed by surgically transecting the main trunk of the facial nerve. This resulted in oropharyngeal dysphagia in mice, with changes in lick and swallowing patterns during drinking and eating [ 15 ]. It was suggested that this injury mouse model could be used to study human dysphagia following facial nerve injury caused by various iatrogenic and idiopathic reasons.…”

“…Animal studies can provide clear and uncomplicated research opportunities and an insightful information to understand dysphagia. In particular, injury or surgical models for dysphagia studies are being developed and validated for examining dysphagia [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. In these animal models, rodents are commonly used to investigate mechanisms underlying nerve or muscle injury, regeneration, and treatment.…”

“…In these animal models, rodents are commonly used to investigate mechanisms underlying nerve or muscle injury, regeneration, and treatment. Recently, rodent models of oropharyngeal dysphagia were developed by inducing nerve injury in the tongue and facial muscles or impeding the movement of the pharynx [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. Injuries associated with dysphagia, such as branch injury of the hypoglossal nerve, facial nerve, vagus nerve, recurrent or superior laryngeal nerve, or other sensory deficits can be replicated relatively easily in animal models.…”