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
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TL;DR: Cricothyroid adduction increases tension to the vocal folds, thus increasing fundamental frequency and upper pitch range, and is indicated for a large range of vocal fold tension problems.
Abstract: Cricothyroid adduction increases tension to the vocal folds, thus increasing fundamental frequency and upper pitch range. We treated 10 patients with cricothyroid muscle dysfunction using this technique. Preoperative electromyographic, acoustic, and perceptual analysis was performed. Intraoperatively the effect of increasing tension on the fundamental, falsetto, and basal frequencies was measured by using a strain gauge to the adducting suture at several tensions and a cervical microphone connected to a pitch meter. Postoperative acoustic and perceptual analysis was then performed up to 18 months later. Analysis of pitch vs. tension curves indicates a near-linear relationship until very high tensions are applied. Statistically significant improvement was achieved in both acoustic and perceptual analysis, although some deterioration was noted between early and late results. Cricothyroid adduction is indicated for a large range of vocal fold tension problems.
17 citations
"Recovery of laryngeal function afte..." refers background in this paper
...It divides into a larger, internal branch which enters the larynx through the thyrohyoid membrane (carrying sensory fibers down to the level of the glottis) and a smaller, external, branch which passes deep to the superior thyroid artery to innervate the cricothyroid muscle responsible for vocal fold lengthening and tension, important for high voice pitch (42)....
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TL;DR: The surgical technique, which includes routine visualization of the external branch of the superior laryngeal nerve, is described and the literature related to the scope of voice complaints after thyroidectomy is reviewed.
Abstract: Voice and swallowing complaints are common after thyroidectomy, but their etiology is not completely understood. Manipulation of the endolaryngeal soft tissues, pharyngeal constrictor muscles, and recurrent laryngeal nerves may all result in symptoms. In addition, the external branch of the superior laryngeal nerve and cricothyroid muscle may play a role in postoperative dysphonia. We review the literature related to the scope of voice complaints after thyroidectomy. We also discuss several studies describing the surgical anatomy of the external branch of the superior laryngeal nerve as it relates to thyroidectomy. Our surgical technique, which includes routine visualization of the external branch of the superior laryngeal nerve, is then described.
14 citations
TL;DR: A mathematical model is used to predict the relationship between height and median nerve CSA between the Indian and Dutch populations and believes it has the potential to reveal a much stronger and more significant relationship between median nerves CSA and a key anthropomorphic variable, height-squared.
Abstract: noted the highest correlation between median nerve CSA and weight at 0.352 in India and 0.239 in Holland for the left wrist, but this measurement was less consistent, 0.232 and 0.126, for the right wrist. We believe their study has the potential to reveal a much stronger and more significant relationship between median nerve CSA and a key anthropomorphic variable, height-squared. Furthermore, we believe that this relationship is likely to apply to all nerves. We recently used a mathematical model to explore the relationship between height, weight, and muscle CSA in Duchenne muscular dystrophy, and a similar approach can be used to explore the relationship between height, weight, and nerve CSA. At the heart of our model is the fundamental geometric relationship between linear dimensions, surface area, and volume. For any 3dimensional object, a doubling of all linear dimensions results in increased area (including any cross-section) by a factor of 4 and volume by a factor of 8. We can use our mathematical model to predict the relationship between height and median nerve CSA between the Indian and Dutch populations. Among the Indians, height was 1.60 6 0.10 m, whereas median CSA was 7.0 6 1.1 and 7.2 6 1.1 for the left and right wrists, respectively, with a mean of 7.1 mm for both. Among the Dutch, mean height was 1.72 1 0.08 m. Thus, the Dutch were (1.72/1.60) 1.075 times taller than the Indians. Therefore, Dutch mean median nerve CSA is predicted to be (1.075) 5 1.156 times greater or 7.1 3 1.156 5 8.2 mm. Indeed, this was the case. Among the Dutch, median CSA was 8.3 6 1.9 and 8.1 6 2.0 for the left and right wrists with a mean of 8.2 mm for both. We hope Walhout-van Burg and colleagues will find our mathematical model and analysis to be of interest and will assess it further by calculating correlation coefficients between height-squared and median nerve CSA for their data. If the proposed relationship between nerve CSA and height-squared is confirmed, taking it into consideration in future studies of median (and other) nerve CSA, conduction, anthropomorphic, and environmental variables will likely improve accuracy and lead to new discoveries.
6 citations