Recovery of laryngeal function after intraoperative injury to the recurrent laryngeal nerve
TL;DR: This review aims to provide an update on the current understandings of surgically-induced injury to the laryngeal nerves to clarify any differences between the transient and permanent injury of the RLN.
Abstract: Loss of function in the recurrent laryngeal nerve (RLN) during thyroid/parathyroid surgery, despite a macroscopically intact nerve, is a challenge which highlights the sensitivity and complexity of laryngeal innervation. Furthermore, the uncertain prognosis stresses a lack of capability to diagnose the reason behind the impaired function. There is a great deal of literature considering risk factors, surgical technique and mechanisms outside the nerve affecting the incidence of RLN paresis during surgery. To be able to prognosticate recovery in cases of laryngeal dysfunction and voice changes after thyroid surgery, the surgeon would first need to define the presence, location, and type of laryngeal nerve injury. There is little data describing the events within the nerve and the neurobiological reasons for the impaired function related to potential recovery and prognosis. In addition, very little data has been presented in order to clarify any differences between the transient and permanent injury of the RLN. This review aims, from an anatomical and neurobiological perspective, to provide an update on the current understandings of surgically-induced injury to the laryngeal nerves.
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TL;DR: This 672-page volume written by a single author contains 26 chapters in seven parts and three appendices and is intended for practicing electromyographers and all those concerned with electrodiagnostic tests in clinical practice.
Abstract: This 672-page volume written by a single author contains 26 chapters in seven parts and three appendices. Part 1 deals with basic anatomy and physiology of the neuromuscular system and basics of electrodiagnosis, including recording apparatus. The next three parts contain nerve conduction studies, tests for neuromuscular transmission, and electromyography, including single-fiber electromyography. Part 5 contains reviews of blink reflex, F wave, H-reflex, and somatosensory evoked potentials. The disorders of the spinal cord, peripheral nervous system, neuromuscular junction, myopathies, and abnormal muscle activity are discussed in the last two parts. The appendices cover a historical review of electrodiagnosis, the fundamentals of electronics, instrumentation, and a glossary of terms approved by the American Association of Electrodiagnosis and Electromyography. The book is intended for practicing electromyographers and all those concerned with electrodiagnostic tests in clinical practice. The author's extensive experience in electrophysiological studies prompted him to write this book. The notable feature
153 citations
TL;DR: The 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, and suggests that neurological variation underlies this pattern.
Abstract: 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, and (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.
27 citations
Cites background from "Recovery of laryngeal function afte..."
..., stretch, crush, sectioning) in patients means that the source of variation in response to nerve injury is unknown [6, 7]....
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TL;DR: To retrospectively determine optimal timing for initiation of nimodipine within a cohort of patients with acute vocal fold paralysis, data are presented on patients diagnosed with VFP in the 1990s.
Abstract: Objectives/hypothesis To retrospectively determine optimal timing for initiation of nimodipine within a cohort of patients with acute vocal fold paralysis (VFP). Study design Retrospective patient review. Methods Subjects were divided into three groups: initiation within 15 days postinjury (n = 19), between 15 and 30 days postinjury (n = 23), or greater than 30 days postinjury (n = 11). Results Fifty-one patients (53 paralyzed vocal folds [VFs]) met entrance criteria and were offered and started off-label nimodipine treatment. Thirty-six of 53 VFs recovered purposeful motion (67.9%). There was no significant difference in the rate of VF recovery among patients who began nimodipine within 15 days (68.4%), patients who started nimodipine between 15 and 30 days (73.9%) of nerve injury (P = .1405), and patients who initiated nimodipine after 30 days postinjury (54.5%). Conclusions Nimodipine treatment for acute VFP yielded equal VF motion recovery rates regardless of when the medication was initiated. Time to recovery of motion was not different between groups studied.
25 citations
TL;DR: Cont-IONM is feasible and safe to use during transoral endoscopic thyroidectomies and may assist in the early detection of adverse EMG changes, thereby preventing paralysis of the RLNs.
Abstract: The novel concept of continuous intraoperative neuromonitoring (Cont-IONM) through stimulation of the vagal nerve has been used in thyroidectomies to prevent imminent injury of the recurrent laryngeal nerve (RLN). This article reports on this technology and the results of using transoral Cont-IONM in natural orifice transluminal endoscopic surgery for thyroid disease. Cont-IONM of the RLN was achieved through automatic cyclical stimulation of the vagal nerve using a C2 monitor and delta stimulating electrode. During the operation, three vestibular incisions were made, and the stimulating electrode was transorally inserted, with its cable line lying outside the trocar. The vagal nerve was gently dissected, looped, and then enveloped by the electrode cuff. Electromyography (EMG) of the vocalis muscle was performed, and the alarm was set to activate when the EMG amplitude reduced by 50% and latency was prolonged by 10%. Demographic data and outcome variables, including incremental time required to achieve Cont-IONM, were obtained. A total of 20 patients (28 nerves at risk) undergoing a transoral endoscopic thyroidectomy vestibular approach were enrolled in this study. All Cont-IONM procedures were successfully completed. In all patients, the stimulation was set at 0.7 milliamps every 1 s, and Cont-IONM use was unassociated with any untoward neural, cardiovascular, or gastrointestinal sequelae. On average, the ipsilateral Cont-IONM procedure required 10.33 ± 2.57 min to complete. Except for one instance, no significant problems occurred with electrode displacement. In one patient, a combined EMG event occurred, which improved after releasing the thyroid retractor, and the patient had no vocal cord paralysis postoperatively. Cont-IONM is feasible and safe to use during transoral endoscopic thyroidectomies and may assist in the early detection of adverse EMG changes, thereby preventing paralysis of the RLNs.
23 citations
References
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TL;DR: Using both traditional qualitative LEMG measurements in addition to turns analysis improves prognostic accuracy in patients with acute vocal fold paralysis who demonstrate voluntary motor activity.
Abstract: Objectives:
Quantitative laryngeal electromyography (LEMG) using turns analysis can differentiate acute vocal fold paralysis from normal controls. The objective of this study is to determine if using both traditional qualitative LEMG measurements in addition to turns analysis improves prognostic accuracy in patients with acute vocal fold paralysis who demonstrate voluntary motor activity.
Study Design:
Retrospective review of LEMG data (qualitative and quantitative) and charts of patients with vocal fold paralysis on flexible laryngoscopy, recurrent laryngeal neuropathy, and varying degrees of motor unit recruitment.
Methods:
Laryngeal EMG using a standardized protocol involving qualitative (evaluation of recruitment, motor unit configuration, detection of fibrillations, synkinesis) and quantitative (turns analysis) measurements was performed. Prognosis was correlated with vocal fold motion recovery status (minimum of 6 months following onset) using positive and negative predictive values (PPV, NPV).
Results:
Twenty-three patients underwent LEMG for acute recurrent laryngeal neuropathy. All four patients with excellent LEMG prognosis recovered motion, whereas 17/19 patients with fair/poor LEMG prognosis were without motion at least 6 months following onset, resulting in a 100% PPV and 89.5% NPV.
Conclusions:
Integrating both qualitative and quantitative LEMG data improves prognostic accuracy in vocal fold paralysis patients who demonstrate voluntary motor unit activity. Laryngoscope, 2012
65 citations
TL;DR: Action potentials were recorded from the m.crico-thyreoideus externus in a case with partial resection of the larynx of normal subjects and of patients with laryngeal paresis and the action potential amplitude was averaged electrically and recorded as an expression of the degree of activity.
Abstract: ELECTROMYOGRAPHY of the internal laryngeal muscles has been applied in the diagnosis of laryngeal palsy by Weddell, Feinstein and Pattle1. In a study of phonation, Katsuki2 recorded action potentials from the m.crico-thyreoideus externus in a case with partial resection of the larynx. In the present study, action potentials were recorded by means of concentric needle electrodes inserted in the m.thyreo-arytaenoideus internus (m.vocalis), crico-thyreoideus externus, inter-arytaenoideus transversus and crico-arytaenoideus posterior (m.posticus) of normal subjects and of patients with laryngeal paresis. In addition, the action potential amplitude was averaged electrically and recorded as an expression of the degree of activity. The subject spoke into a condenser microphone, the output of which was amplified and recorded simultaneously with the action potentials.
63 citations
"Recovery of laryngeal function afte..." refers background in this paper
...Laryngeal electromyography (LEMG) was first introduced more than sixty years ago, and has evolved (72) into a valuable tool for laryngologists in diagnosing neurolaryngological disorders....
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TL;DR: A ‘semicircular’ compartment of the rat thyropharyngeus muscle at the pharyngoesophageal junction is identified and the glycogen depletion method is used to determine how the fibers of this muscle are innervated by different cranial nerve branches.
Abstract: We identified a 'semicircular' compartment of the rat thyropharyngeus muscle at the pharyngoesophageal junction and used the glycogen depletion method to determine how the fibers of this muscle (as well as all others of the pharynx and larynx) are innervated by different cranial nerve branches. The semicircular compartment appears anatomically homologous to the human cricopharyngeus muscle, an important component of the upper esophageal sphincter. While we found very little overlap in the muscle targets of the pharyngeal, superior laryngeal and recurrent laryngeal nerves within the pharynx and larynx, the semicircular muscle receives a dual, interdigitating innervation from two vagal branches: the pharyngeal nerve and a branch of the superior laryngeal nerve we call the dorsal accessory branch. After applying horseradish peroxidase to either of these two nerves, we compared the distribution and number of cells labeled in the brainstem. The dorsal accessory branch conveys a more heterogeneous set of efferent fibers than does the pharyngeal nerve, including the axons of pharyngeal and esophageal motor neurons and parasympathetic preganglionic neurons. The observed distribution of labeled motor neurons in nucleus ambiguus also leads us to suggest that the semicircular compartment is innervated by two subsets of motor neurons, one of which is displaced ventrolateral to the main pharyngeal motor column. This arrangement raises the possibility of functional differences among semicircular compartment motor neurons correlated with the observed differences in brainstem location of cell bodies.
59 citations
"Recovery of laryngeal function afte..." refers background in this paper
...The lower motor neurons of the special efferent system controlling the intrinsic laryngeal muscles are located in the nucleus ambiguus in the lower brainstem, in a fairly well-studied somatotopical arrangement (22-30)....
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TL;DR: Sternothyroid muscle division is occasionally employed during thyroidectomy to gain superior pedicle exposure, but division of this muscle does not appear to be associated with adverse functional voice outcome, and should be utilized at surgeon discretion during Thyroidectomy.
Abstract: Post-thyroidectomy voice dysfunction may occur in the absence of laryngeal nerve injury. Strap muscle division has been hypothesized as one potential contributor to dysphonia. Vocal-function data, prospectively recorded before and after thyroidectomy from two high-volume referral institutions, were utilized. Patient-reported symptoms, laryngoscopic, acoustic, and aerodynamic parameters were recorded at 2 weeks and 3 months postoperatively. Patients with and without sternothyroid muscle division during surgery were compared for voice changes. Patients with laryngeal nerve injury, sternohyoid muscle division, arytenoid subluxation or no early postoperative follow-up evaluation were excluded. Differences between study groups and outcomes were compared using t-tests and rank-sum tests as appropriate. Of 84 patients included, 45 had sternothyroid division. Distribution of age, gender, extent of thyroidectomy, specimen size, and laryngeal nerve identification rates did not differ significantly between groups. There was a significant predilection for or against sternothyroid muscle division according to medical center. No significant difference in reported voice symptoms was observed between groups 2 weeks or 3 months after thyroidectomy. Likewise, acoustic and aerodynamic parameters did not differ significantly between groups at these postoperative study time points. Sternothyroid muscle division is occasionally employed during thyroidectomy to gain superior pedicle exposure. Division of this muscle does not appear to be associated with adverse functional voice outcome, and should be utilized at surgeon discretion during thyroidectomy.
57 citations
"Recovery of laryngeal function afte..." refers background in this paper
...Dividing the sternothyroid muscle has been shown not to affect voice outcome in a significant way (15)....
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TL;DR: The location and axonal projections of laryngeal motoneurons (LMn) have been studied in rats and cats using horseradish peroxidase as a retrograde tracer.
56 citations
"Recovery of laryngeal function afte..." refers background in this paper
...The lower motor neurons of the special efferent system controlling the intrinsic laryngeal muscles are located in the nucleus ambiguus in the lower brainstem, in a fairly well-studied somatotopical arrangement (22-30)....
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