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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1,975 citations
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: An accurate morphological description of the posterior cricoarytenoid muscle nerve supply is established in a large sample of human larynges to establish an accurate knowledge of the nerve supply of each individual muscle.
Abstract: Objectives/Hypothesis To achieve a successful selective reinnervation of the larynx, an accurate knowledge of the nerve supply of each individual muscle is required. The posterior cricoarytenoid muscle, the only abductor or respiratory muscle of the larynx, plays a vital role in cases of recurrent palsy and orthotopic transplantation. Descriptions of the posterior cricoarytenoid muscle nerve supply pattern vary considerably. The goal of the present study was to establish an accurate morphological description of the posterior cricoarytenoid muscle nerve supply in a large sample of human larynges.
Study Design Morphologic study of human larynges.
Methods The posterior cricoarytenoid muscle nerve supply was studied in a total sample of 75 human larynges obtained from necropsies (47 male and 28 female samples; age range, 41–95 y) and examined by careful dissection using a surgical microscope.
Results The posterior cricoarytenoid muscle nerve supply in all cases (100%) came from the anterior division of the recurrent nerve. However, in six cases (4%) a small branch also arose from the ramus anastomoticus. The number of branches coming from the anterior division varied, ranging from one to six. The two-branch pattern was the most frequent (42.7%), followed by the three-branch pattern (34%) and the one-branch pattern (7.3%). The remaining 16% of cases showed patterns of four, five, or six branches. When two or more branches were present, a connection between them was observed in 64% of cases. Five different types of origin of the various branches were observed along the course of the recurrent nerve in relation to the cricothyroid joint: type a, vertical segment below the cricothyroid joint (7.5%); type b) vertical segment behind the cricothyroid joint (40.5%); type c) vertical segment just above the cricothyroid joint (16%); type ) from the genu, in common with the arytenoid branch, above the cricothyroid joint and just below the cricoarytenoid joint (34%); and type e) oblique segment (2%).
Conclusion Despite the variability of the innervation of the posterior cricoarytenoid muscle and its strong connection with the interarytenoid nerve, this should not preclude successful reinnervation.
40 citations
"Recovery of laryngeal function afte..." refers background in this paper
...The anterior branch carries motor fibers (33,34) to the posterior thyroarytenoid muscle, lateral cricoarytenoid muscle and, finally, to the thyroarytenoid muscle (35-37)....
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TL;DR: To confirm the value of using laryngeal electromyography (LEMG) to predict the long‐term prognosis of unilateral vocal fold paralysis (UVFP), and elucidate the adequate timing of LEMG.
Abstract: Objectives/Hypothesis
To confirm the value of using laryngeal electromyography (LEMG) to predict the long-term prognosis of unilateral vocal fold paralysis (UVFP), and elucidate the adequate timing of LEMG.
Study Design
Prospective cohort prognosis study.
Methods
The LEMG data of 84 patients with UVFP were prospectively collected, and 81 patients received follow-up at least 6 months after symptom onset. If the paralyzed vocal fold had <20% recruitment reduction during phonation compared to the normal vocal fold signals, and absence of fibrillation when the patient was silent, the prognosis was considered to be good (negative finding). Otherwise, the prognosis was considered to be poor (positive finding). The association between UVFP outcome and LEMG prognostic rules and the accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of LEMG were calculated.
Results
The mean duration of LEMG after symptom onset was 3.7 months, and follow-up after symptoms onset was 18.4 months. Sixty-six of 71 patients with a positive finding had persistent UVFP; four of 10 patients with a negative finding recovered vocal fold motion. LEMG results were significantly associated with the outcome of UVFP (P = .007). The overall accuracy, sensitivity, specificity, PPV, and NPV of LEMG were 86.4%, 91.7%, 44.4%, 93.0%, and 40.0%, respectively. When LEMG was done more than 2 months after symptom onset, the PPV was 97.9%.
Conclusions
LEMG has a high PPV in predicting the long-term outcome of UVFP patients with poor prognosis. Permanent laryngeal framework surgery is feasible if patients have positive findings at least 2 months after symptom onset.
Level of Evidence
1b Laryngoscope, 125:898–903, 2015
38 citations
"Recovery of laryngeal function afte..." refers background in this paper
...But LEMG has nevertheless been shown to have high positive predictive value in predicting the long-term outcome of patients with a poor prognosis (74-77) and it is used widely to predict...
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...Patients with pathological electromyographic findings at least two months after the paresis are most likely to need laryngeal framework surgery (76)....
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TL;DR: By selectively blocking the ESLN using lidocaine, this work attempted to identify the salient laryngeal features associated with acute, unilateral cricothyroid (CT) muscle dysfunction.
Abstract: Objectives/Hypothesis:
For over 100 years, a controversy has existed regarding the laryngeal signs that should be considered pathognomonic of unilateral external superior laryngeal nerve (ESLN) paralysis. By selectively blocking the ESLN using lidocaine, we attempted to identify the salient laryngeal features associated with acute, unilateral cricothyroid (CT) muscle dysfunction.
Study Design:
Prospective, repeated measures, experimental design.
Methods:
Ten vocally normal adult males underwent lidocaine block of the right ESLN with laryngeal electromyography verification. Flexible videolaryngostroboscopic (FVLS) recordings were acquired before and during the block. Eleven blinded, expert judges, rated randomized pre- versus during block recordings of 10 vocal tasks using standardized FVLS rating protocols.
Results:
Contrary to recent clinical reports, no evidence of hypomobility/sluggishness of the ipsilateral vocal fold, or a consistent pattern of axial rotation of the larynx was observed. Instead, the analysis revealed: 1) deviation of the petiole of the epiglottis to the side of weakness in 60% of participants during a glissando up maneuver produced at normal volume, and 2) axial rotation of the posterior commissure to the left and the anterior commissure to the right in 50% of participants during a maneuver which rapidly alternated between a maximum vocal fold abduction task (sniff) and a high-pitched “ee” production.
Conclusions:
Neither of these laryngeal findings has been reported previously. They potentially represent valuable diagnostic markers of acute, unilateral CT paralysis. Clinical populations need to be explored to better appreciate the diagnostic value and precision of these laryngeal signs. Laryngoscope, 2009
37 citations
TL;DR: A qualitative and quantitative investigation of the location of the motoneurons innervating the intrinsic laryngeal muscles of rats found that a superimposition of CT and posterior cricoarytenoid (PCA) mot oneurons was observed in the rostral third of the NA.
Abstract: This paper describes a qualitative and quantitative investigation of the location of the motoneurons innervating the intrinsic laryngeal muscles of rats. Injections of horseradish peroxidase, Diamidino Yellow and True Blue were made either in one or, simultaneously, in three laryngeal muscles. Unlike those in cats and rabbits, the motoneurons that make up the nucleus ambiguus (NA) in rats are not arranged in two separate subgroups, that is one belonging to the cricothyroid (CT) motoneurons and the other to the rest of the intrinsic laryngeal motoneurons. Instead, a superimposition of CT and posterior cricoarytenoid (PCA) motoneurons was observed in the rostral third of the NA. Motoneurons innervating the PCA, thyroarytenoid (TA) and lateral cricoarytenoid (LCA) muscle overlap in the medial third of the NA. Finally, in the region of the NA caudal to the obex, the TA and LCA motoneurons also overlap. Labeled motoneurons were located in the ipsilateral side to the injected muscle in all cases.
36 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: It is hypothesized that racial and gender variations in prevalence of branched RLN exist and that they conveys an increased risk of nerve injury during thyroid surgery.
Abstract: Objectives/Hypothesis
The extralaryngeal branching of recurrent laryngeal nerves (RLN) conveys an increased risk of nerve injury during thyroid surgery. We hypothesized that racial and gender variations in prevalence of branched RLN exist.
Study Design
A retrospective review of all patients who underwent thyroid surgery in a 4-year period in a single surgeon practice.
Methods
The RLN was routinely identified during thyroid surgery. Presence of RLN branching, its distance from the laryngeal nerve entry point (NEP), and functionality of the branches were ascertained. Patient demographics, rates of neural branching, and distance of bifurcation from the NEP were evaluated using statistical analysis.
Results
We identified 719 RLNs at risk in 491 patients who underwent central neck surgery. Four hundred and five (82.5%) patients were female and 86 (17.5%) patients were male. There were 218 (44.4%) African American patients and 251 (51.1 %) Caucasian patients.
In African American patients, 42.1% RLNs bifurcated compared to 33.2% RLNs in Caucasian (P = 0.017) patients. The RLNs of African American and Caucasian patients bifurcated at comparable distances (P = 0.30).
In male patients, 39.1% RLNs bifurcated; whereas in female patients 36.2% RLNs bifurcated (P = 0.53). On average, RLN bifurcation in female patients was at a longer distance from NEP compared to that of male patients (P = 0.012). Electrophysiologic testing found motor fibers in all anterior branches and three posterior extralaryngeal RLN branches.
Conclusion
African American patients have a higher rate of RLN bifurcation compared to Caucasian patients but no statistically significant difference in distance from NEP. Female patients tend to have longer branching variants of bifid RLNs. RLN motor fibers reside primarily in the anterior branch but may occur in the posterior branch.
Level of Evidence
4. Laryngoscope 124:2433–2437, 2014
35 citations
"Recovery of laryngeal function afte..." refers background in this paper
...The branching point is located either inside the larynx, or, as in roughly one third of cases, before the nerve entering point (31)....
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