Protective Glottic Closure: Biomechanical Effects of Selective Laryngeal Denervation

Recurrent laryngeal nerve (RLN) injury in neonates, a complication of patent ductus arteriosus corrective surgery, leads to aspiration and swallowing complications. Severity of symptoms and prognosis for recovery are variable. We transected the RLN unilaterally in an infant mammalian animal model to characterize the degree and variability of dysphagia in a controlled experimental setting. We tested the hypotheses that 1) both airway protection and esophageal function would be compromised by lesion, 2) given our design, variability between multiple post-lesion trials would be minimal, 3) variability among individuals would be minimal. Individuals' swallowing performance was assessed pre- and post-lesion using high speed VFSS. Aspiration was assessed using the Infant Mammalian Penetration Aspiration Scale (IMPAS). Esophageal function was assessed using two measures devised for this study. Our results indicate that RLN lesion leads to increased frequency of aspiration, and increased esophageal dysfunction, with significant variation in these basic patterns at all levels. On average, aspiration worsened with time post-lesion. Within a single feeding sequence, the distribution of unsafe swallows varied. Individuals changed post-lesion either by increasing average IMPAS score, or by increasing variation in IMPAS score. Unilateral RLN transection resulted in dysphagia with both compromised airway protection and esophageal function. Despite consistent, experimentally controlled injury, significant variation in response to lesion remained. Aspiration following RLN lesion was due to more than unilateral vocal fold paralysis. We suggest that neurological variation underlies this pattern.

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“…non-lapping). Several other investigators use the infant pig as a model for studying swallowing problems [23–27]. …”

Section: Introductionmentioning

confidence: 99%

The Physiologic Impact of Unilateral Recurrent Laryngeal Nerve (RLN) Lesion on Infant Oropharyngeal and Esophageal Performance

et al. 2015

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“…It has been reported that bilateral SLN lesions result in a significantly high incidence of aspiration [5, 6] and that unilateral sensory loss of the laryngopharynx can cause aspiration as well [7]. Sasaki et al [8] reported that a unilateral SLN lesion results in reduced force of glottic closure in the pig, and they implied that this could contribute to laryngeal aspiration. Using a different style of experiment, Amis et al [9, 10] reported that stimulation of the external SLN (eSLN) in dogs activates the cricothyroid muscle and causes both pharyngeal dilation and glottis constriction.…”

Section: Introductionmentioning

confidence: 99%

Unilateral Superior Laryngeal Nerve Lesion in an Animal Model of Dysphagia and Its Effect on Sucking and Swallowing

et al. 2013

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We tested two hypotheses relating to the sensory deficit that follows a unilateral superior laryngeal nerve (SLN) lesion in an infant animal model. We hypothesized that it would result in (1) a higher incidence of aspiration and (2) temporal changes in sucking and swallowing. We ligated the right-side SLN in six 2–3-week-old female pigs. Using videofluoroscopy, we recorded swallows in the same pre- and post-lesion infant pigs. We analyzed the incidence of aspiration and the duration and latency of suck and swallow cycles. After unilateral SLN lesioning, the incidence of silent aspiration during swallowing increased from 0.7 to 41.5 %. The durations of the suck containing the swallow, the suck immediately following the swallow, and the swallow itself were significantly longer in the post-lesion swallows, although the suck prior to the swallow was not different. The interval between the start of the suck containing a swallow and the subsequent epiglottal movement was longer in the post-lesion swallows. The number of sucks between swallows was significantly greater in post-lesion swallows compared to pre-lesion swallows. Unilateral SLN lesion increased the incidence of aspiration and changed the temporal relationships between sucking and swallowing. The longer transit time and the temporal coordinative dysfunction between suck and swallow cycles may contribute to aspiration. These results suggest that swallow dysfunction and silent aspiration are common and potentially overlooked sequelae of unilateral SLN injury. This validated animal model of aspiration has the potential for further dysphagia studies.

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“…In this regard, would the authors alternatively consider the strength of glottic closure rather than cordal apposition alone to determine the effectiveness of laryngeal protection? The data in this regard appear as plausible for dysphagia arising by the loss of motor function as one might attribute to the loss of localized sensory function [2]. We do not doubt that voice and swallow therapy are helpful.…”

Section: Commentmentioning

confidence: 71%

Comments on Selected Recent Dysphagia Literature

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Protective Glottic Closure: Biomechanical Effects of Selective Laryngeal Denervation

Cited by 26 publications

References 13 publications

The Physiologic Impact of Unilateral Recurrent Laryngeal Nerve (RLN) Lesion on Infant Oropharyngeal and Esophageal Performance

The Physiologic Impact of Unilateral Recurrent Laryngeal Nerve (RLN) Lesion on Infant Oropharyngeal and Esophageal Performance

Unilateral Superior Laryngeal Nerve Lesion in an Animal Model of Dysphagia and Its Effect on Sucking and Swallowing

Comments on Selected Recent Dysphagia Literature

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