Two trajectories of functional recovery in thyroid surgery related unilateral vocal cord paralysis.

BACKGROUND: Iatrogenic unilateral vocal fold paralysis caused by thyroid surgery induces profound physical and psychosocial distress in patients. The natural course of functional recovery over time differs substantially across subjects, but the mechanisms underlying this difference remain unclear. In this study, we examined whether the anatomic site of the lesion affected the trajectory of recovery. METHODS: In this prospective case series study in a single medical center, patients with thyroid surgery-related unilateral vocal fold paralysis were evaluated using quantitative laryngeal electromyography, videolaryngostroboscopy, voice acoustic analysis, the Voice Outcome Survey, and the Short Form-36 quality-of-life questionnaire. Patients with and without superior laryngeal nerve injuries were compared. RESULTS: Forty-two patients were recruited, among whom 15 and 27 were assigned to the with and without superior laryngeal nerve injury groups, respectively. Compared with the group without superior laryngeal nerve injury, the group with superior laryngeal nerve injury group demonstrated less improvement in the recruitment of vocal fold adductors, and the group also had more severe impairment of vocal fold vibration, maximum phonation time, jitter, shimmer, and harmony-to-noise ratio at the first evaluation. This difference was also found in the glottal gap and maximum phonation time 12 months after the injury. CONCLUSION: Among patients with thyroid surgery-related unilateral vocal fold paralysis, superior laryngeal nerve injury induces a distinctively different recovery trajectory compared with those without superior laryngeal nerve injury characterized by less reinnervation of vocal fold adductors and worse presentation in terms of the glottal gap and maximum phonation time. This study emphasizes the importance of superior laryngeal nerve function and its preservation in thyroid surgery.

Cricopharyngeal myotomy for delayed Cricopharyngeal dysfunction after head and neck surgery - case report.

BACKGROUND: Head and neck surgeries can perturb normal structures of neck muscles and nerve innervations, which are supposed to function in harmony to allow complicated process like swallowing. It is still likely that cricopharyngal dysfunction emerges years after the head and neck surgeries. CASE PRESENTATION: We report a case with history of left unilateral vocal cord immobility and development of dysphagia and aspiration 2 years after radical thyroidectomy with neck lymph nodes dissection and medialization thyroplasty. Cricopharyngeal dysfunction was impressed and was confirmed with visualization of cricopharyngeal narrowing segment in radiographic contrast swallow examination. The patient was treated successfully by cricopharyngeal myotomy, achieving long-term relief in our 4 years of follow up. CONCLUSIONS: Our case of delayed cricopharyngal dysfunction after radical thyroidectomy and medialization thyroplasty shows that it is important to follow up swallowing functions after patients with UVCI undergo medialization thyroplasty. In the event of delayed manifestation of cricopharyngeal function, it can still be treated successfully by cricoharyngeal myotomy, achieving long term relief of dysphagia.

Laryngeal and vocal alterations after thyroidectomy / Alterações laríngeas e vocais após tireoidectomia

Abstract Introduction: Dysphonia is a common symptom after thyroidectomy. Objective: To analyze the vocal symptoms, auditory-perceptual and acoustic vocal, videolaryngoscopy, the surgical procedures and histopathological findings in patients undergoing thyroidectomy. Methods: Prospective study. Patients submitted to thyroidectomy were evaluated as follows: anamnesis, laryngoscopy, and acoustic vocal assessments. Moments: pre-operative, 1st post (15 days), 2nd post (1 month), 3rd post (3 months), and 4th post (6 months). Results: Among the 151 patients (130 women; 21 men). Type of surgery: lobectomy + isthmectomy n = 40, total thyroidectomy n = 88, thyroidectomy + lymph node dissection n = 23. Vocal symptoms were reported by 42 patients in the 1st post (27.8%) decreasing to 7.2% after 6 months. In the acoustic analysis, f0 and APQ were decreased in women. Videolaryngoscopies showed that 144 patients (95.3%) had normal exams in the preoperative moment. Vocal fold palsies were diagnosed in 34 paralyzes at the 1st post, 32 recurrent laryngeal nerve (lobectomy + isthmectomy n = 6; total thyroidectomy n = 17; thyroidectomy + lymph node dissection n = 9) and 2 superior laryngeal nerve (lobectomy + isthmectomy n = 1; Total thyroidectomy + lymph node dissection n = 1). After 6 months, 10 patients persisted with paralysis of the recurrent laryngeal nerve (6.6%). Histopathology and correlation with vocal fold palsy: colloid nodular goiter (n = 76; palsy n = 13), thyroiditis (n = 8; palsy n = 0), and carcinoma (n = 67; palsy n = 21). Conclusion: Vocal symptoms, reported by 27.8% of the patients on the 1st post decreased to 7% in 6 months. In the acoustic analysis, f0 and APQ were decreased. Transient paralysis of the vocal folds secondary to recurrent and superior laryngeal nerve injury occurred in, respectively, 21% and 1.3% of the patients, decreasing to 6.6% and 0% after 6 months.

Resumo Introdução: A disfonia é um sintoma comum após a tireoidectomia. Objetivo: Analisar os sintomas vocais, auditivo-perceptivos e acústica vocal, videolaringoscopia, procedimento cirúrgico e achados histopatológicos em pacientes submetidos à tireoidectomia. Método: Estudo prospectivo. Pacientes submetidos à tireoidectomia foram avaliados da seguinte forma: anamnese, laringoscopia e avaliações vocais acústicas. Momentos: pré-operatório, 1ª avaliação pós (15 dias), 2ª avaliação pós (1 mês), 3ª avaliação pós (3 meses) e 4ª avaliação pós-operatória (6 meses). Resultados: Dos 151 pacientes, 130 eram mulheres e 21, homens. Tipos de cirurgia: lobectomia + istmectomia n = 40, tireoidectomia total n = 88, tireoidectomia + dissecção de linfonodo n = 23. Sintomas vocais foram relatados por 42 pacientes na 1ª avaliação pós-operatória (27,8%), reduzidos para 7,2% após 6 meses. Na análise acústica, f0 e APQ estavam diminuídos nas mulheres. As videolaringoscopias mostraram que 144 pacientes (95,3%) tiveram exames normais no momento pré-operatório. Paralisia das cordas vocais foi diagnosticada em 34 pacientes na 1ª avaliação pós-operatória, 32 do nervo laríngeo recorrente (lobectomia + istmectomia - n = 6; tireoidectomia total - n = 17; tireoidectomia total + dissecção de linfonodos - n = 9) e 2 do nervo laríngeo superior (lobectomia + istmectomia - n = 1; tireoidectomia total + dissecção de linfonodos - n = 1). Após 6 meses, 10 pacientes persistiram com paralisia do nervo laríngeo recorrente (6,6%). Histopatologia e correlação com paralisia das cordas vocais: bócio coloide nodular (n = 76; paralisia n = 13), tireoidite (n = 8; paralisia n = 0) e carcinoma (n = 67; paralisia n = 21). Conclusão: Os sintomas vocais, relatados por 27,8% dos pacientes na 1ª avaliação pós-operatória, diminuíram para 7% em 6 meses. Na análise acústica, f0 e APQ diminuíram. A paralisia transitória de cordas vocais secundária à lesão do nervo laríngeo recorrente e nervo laríngeo superior ocorreu, respectivamente, em 21% e 1,3% dos pacientes, reduziu-se para 6,6% e 0% após 6 meses.

Laryngeal and vocal alterations after thyroidectomy.

INTRODUCTION: Dysphonia is a common symptom after thyroidectomy. OBJECTIVE: To analyze the vocal symptoms, auditory-perceptual and acoustic vocal, videolaryngoscopy, the surgical procedures and histopathological findings in patients undergoing thyroidectomy. METHODS: Prospective study. Patients submitted to thyroidectomy were evaluated as follows: anamnesis, laryngoscopy, and acoustic vocal assessments. Moments: pre-operative, 1st post (15 days), 2nd post (1 month), 3rd post (3 months), and 4th post (6 months). RESULTS: Among the 151 patients (130 women; 21 men). Type of surgery: lobectomy+isthmectomy n=40, total thyroidectomy n=88, thyroidectomy+lymph node dissection n=23. Vocal symptoms were reported by 42 patients in the 1st post (27.8%) decreasing to 7.2% after 6 months. In the acoustic analysis, f0 and APQ were decreased in women. Videolaryngoscopies showed that 144 patients (95.3%) had normal exams in the preoperative moment. Vocal fold palsies were diagnosed in 34 paralyzes at the 1st post, 32 recurrent laryngeal nerve (lobectomy+isthmectomy n=6; total thyroidectomy n=17; thyroidectomy+lymph node dissection n=9) and 2 superior laryngeal nerve (lobectomy+isthmectomy n=1; Total thyroidectomy+lymph node dissection n=1). After 6 months, 10 patients persisted with paralysis of the recurrent laryngeal nerve (6.6%). Histopathology and correlation with vocal fold palsy: colloid nodular goiter (n=76; palsy n=13), thyroiditis (n=8; palsy n=0), and carcinoma (n=67; palsy n=21). CONCLUSION: Vocal symptoms, reported by 27.8% of the patients on the 1st post decreased to 7% in 6 months. In the acoustic analysis, f0 and APQ were decreased. Transient paralysis of the vocal folds secondary to recurrent and superior laryngeal nerve injury occurred in, respectively, 21% and 1.3% of the patients, decreasing to 6.6% and 0% after 6 months.

Effect of wound massage on neck discomfort and voice changes after thyroidectomy.

BACKGROUND: Neck discomfort and voice change are common complications after thyroidectomy. These symptoms might be due to damaged laryngeal nerves, intrinsic structures, or extralaryngeal muscles. They can also occur without injury to any structure as with wound adhesion after thyroidectomy. The objective of this study was to determine causes of neck discomfort and voice change after thyroidectomy and to evaluate the effect of wound massage on symptom relief. METHODS: Forty-five female patients who underwent total thyroidectomy were included (21 in the experimental group and 24 in the control group). Wound massage was used as an intervention to release surgical adhesion. After wound massage education, participants in the experimental group received wound massage from 4 to 12 weeks after thyroidectomy. Analysis was performed for both groups. RESULTS: No laryngeal pathology was found after thyroidectomy. The experimental group had significantly better recovery from surgical adhesion and subjective visual analog scale, voice impairment score, and swallowing impairment score (all P < .01) compared with the control group. Voice analysis results associated with laryngeal movement (speaking fundamental frequency, voice range profile maximum, voice range profile range) also indicated significant recovery (P < .01) in the experimental group. These results indicate that local adhesion after thyroidectomy might affect general movement of the larynx and that wound massage could help patients recover normal general movement of the larynx. CONCLUSION: Neck discomfort and voice change after thyroidectomy are related to local wound adhesion, possibly associated with impairment of laryngeal vertical movement. Release of wound adhesion could help patients recover from neck discomfort and voice changes after thyroidectomy.

Revisiting the autoconditioning hypothesis for acquired reactivity to ultrasonic alarm calls.

Rats emit 22 kHz ultrasonic vocalizations (USVs) in association with pain, fear, or distress. Whereas the capacity to produce USVs is innate, reactivity to them appears to require experience. Specifically, 22 kHz USVs fail to elicit freezing behavior in naïve laboratory rats. However, these "alarm calls" do elicit freezing in rats that previously experienced foot shocks. These findings led to the hypothesis that acquired reactivity is based on "autoconditioning"-learning in which self-generated 22 kHz USVs serve as Pavlovian cues that become associated with foot shocks. The current study tested the autoconditioning hypothesis by devocalizing rats through a unilateral transection of the recurrent laryngeal nerve (Experimental group). Subsequently, animals in both the Experimental and sham-operated Control groups received five unsignaled foot shocks. One or two days later, both groups were tested for USV-elicited freezing in a novel context. Recurrent laryngeal nerve transection failed to prevent or even diminish USV-elicited freezing. In fact, both groups showed large and comparable increases in freezing to USV presentations. A subset of Control animals failed to vocalize during conditioning, while some Experimental animals did vocalize during conditioning. Animals were therefore re-grouped and reanalyzed based on whether they vocalized during conditioning. Again, both groups showed large and comparable increases in USV-elicited freezing. These results disconfirm the essential tenet or prediction of the autoconditioning hypothesis. Alternative mechanisms for acquired reactivity to 22 kHz USVs are therefore considered.

Is the superior laryngeal nerve really safe when using harmonic focus in total thyroidectomy? A prospective randomized study.

BACKGROUND: Harmonic focus (HF) was introduced in thyroid surgery in an effort to reduce operation time and complications. OBJECTIVE: The present study aimed to compare function of superior laryngeal nerve and incidence of other postoperative complications in total thyroidectomies using HF and conventional ligation (CL). METHODS: The trial is a randomized single-center, single-blinded study. Patients aged ≥ 18 years scheduled for total thyroidectomy were considered for participation. An ultrasonic dissector was used for coagulation and cutting in the HF group, while the standard technique was used in the CL group. Demographic, surgical data, and complications were recorded. Data were analyzed using SPSS for Windows. RESULTS: Of 244 eligible patients, data of 206 patients who completed the study were analyzed. The groups were similar in terms of age, sex, and indication for operation. The mean operative time in the HF group was significantly shorter than that in CL group (p=0.01). Drain necessity, duration of drainage, duration of postoperative hospitalization, and the incidence of postoperative complications was similar in the groups (p>0.05). The external branch of the superior laryngeal nerve and recurrent laryngeal nerve palsy were noted in three and two patients in the HF group and in two and one patients in the CL group at 6 months. CONCLUSION: To the best of our knowledge, this is the first study comparing conventional technique with HF in total thyroidectomy, focusing on the function of the external branch of the superior laryngeal nerve using laryngostroboscopy; results showed that HF is as safe as the conventional technique.

Laryngeal electromyographic changes in postthyroidectomy patients with normal vocal cord mobility.

Thyroidectomy has been used for the treatment of thyroid disease for more than 100 years. In spite of the advancement of surgical techniques, there is still a risk of laryngeal nerve injury. The risk of partial or complete injury still depends on some surgical and disease-related factors. The aim of this study is to show the partial injury and to establish these risk factors via laryngeal electromyographic analysis (LEMG) in postthyroidectomy patients with normal vocal cord motion and mucosal anatomy. Patients who had undergone thyroid surgery were enrolled in this prospective study. LEMG analysis was performed to all patients with normal vocal cord mobility preoperatively and was repeated after the first and the third months of surgery. Thyroarytenoid (TA) and cricothyroid (CT) muscles were used to evaluate recurrent and external branch of superior laryngeal nerves, respectively. Four of the 32 patients had mild-to-moderate degrees of partial LEMG changes during preoperative LEMG analysis of TA and CT muscles on each side. After 3 months of surgery, there was a statistically significant worsening of LEMG findings in the right and left external branches of superior and left recurrent laryngeal nerves. Disease and surgery-related risk factors were analyzed. However, there was no significant relationship on the progression of LEMG findings according to these parameters. This is the first prospective study which supports the risk of progression of LEMG changes in patients with normal laryngoscopic examination after thyroid surgery. No reliable significant risk factor was found influencing the LEMG progression.

Carotid endarterectomy significantly improves postoperative laryngeal sensitivity.

OBJECTIVE: Iatrogenic injury of the vagus nerve or its branches during carotid endarterectomy (CEA) can result in globus sensation, dysphagia, and even vocal fold immobility. Knowledge of morphologic and functional laryngopharyngeal outcomes after CEA is poor. The present study was performed to determine potential iatrogenic damage to the laryngeal innervation after CEA. An area of particular interest was the supraglottic sensory threshold, which was examined by Fiberoptic Endoscopic Evaluation of Swallowing With Sensory Testing (FEESST; Pentax Medical Company, Montvale, NJ), a validated and safe method for the determination of the motor and sensory components of swallowing. METHODS: FEESST was used preoperatively in 32 patients scheduled to undergo CEA and twice postoperatively to examine the motor and sensory components of swallowing. In this endolaryngeal examination, laryngopharyngeal sensory thresholds (in mm Hg) were defined as normal at <4.0 mm Hg air pulse pressure (APP), moderate deficit at 4.0 to 6.0 mm Hg APP, or severe deficit at >6.0 mm Hg APP, with a value >10.0 mm Hg APP indicating abolished laryngeal adductor reflex. Acoustic voice parameters were also analyzed for further functional changes of the larynx. RESULTS: The mean ± standard deviation preoperative FEESST measures showed no significant differences (P = .065) between the operated-on side (6.73 ± 1.73 mm Hg) and the opposite side (5.83 ± 1.68 mm Hg). At 2 days postoperatively, the threshold increased (P = .001) to 7.62 ± 1.98 mm Hg on the operated-on side. A laryngopharyngeal mucosal hematoma on the operated side was endoscopically detectable in eight patients (30.8%); in these patients, we found a markedly elevated (P = .021) measure of 9.50 ± 0.93 mm Hg. On the opposite (nonoperated-on) side of the laryngopharynx, the thresholds remained at the same level as preoperatively over all assessments (P >.05), whereas the differences between the operated and nonoperated-on sides and the hematoma and nonhematoma groups were highly significant (P = .004 and P = .001, respectively). Surprisingly, the sensory threshold on the operated-on side (6.08 ± 2.02 mm Hg) decreased significantly at the 6-week follow-up, even in relation to the preoperative measure (P = .022). With the exception of one patient with permanent unilateral vocal fold immobility, no signs of nerve injury were detected. CONCLUSIONS: In accordance with previous reports, injuries to the recurrent laryngeal nerve during CEA seem to be rare. In most patients, postoperative symptoms (globus, dysphagia, dysphonia) and signs fade within a few weeks without any specific therapeutic intervention. This study shows an improved long-term postoperative superior laryngeal nerve function with regard to laryngopharyngeal sensitivity.

Blockade of glial-derived neurotrophic factor in laryngeal muscles promotes appropriate reinnervation.

OBJECTIVES/HYPOTHESIS: Synkinetic reinnervation of the laryngeal muscles is one of the causes of the poor functional recovery after a recurrent laryngeal nerve (RLN) injury. Glial-derived neurotrophic factor (GDNF) is elevated in rat laryngeal muscles during RLN reinnervation. The specific aim of this investigation was to evaluate the effect of anti-GDNF on RLN reinnervation. METHODS: Anti-GDNF antibody was injected into the posterior cricoarytenoid (PCA) 3 days following RLN transection and anastomosis. Larynges were harvested at 7, 14, 28, 56, and 112 days post injury (DPI). Prior to sacrifice, the vocal fold mobility was assessed. Immunostaining to identify neuromuscular junctions was used to evaluate the extent of axonal reinnervation of the PCA, lateral thyroarytenoid (LTA), and medial thyroarytenoid (MTA). RESULTS: After anti-GDNF injection into PCA, RLN reinnervation in all muscles was altered when compared to the controls. PCA innervation was delayed. At 7 DPI, only a few axons made synapses in the PCA. In contrast, axons prematurely innervated the LTA and MTA when compared to controls. Innervation was similar to controls at 56 and 112 DPI. Vocal fold motion was enhanced in 10 of 24 animals studied. CONCLUSIONS: After injection of anti-GDNF into the PCA, early arriving axons bypass the PCA and enter the LTA. Later arriving axons innervate the PCA and MTA. Vocal fold function is improved as compared to controls. Anti-GDNF injection into the PCA influences the pattern of reinnervation and may result in less synkinetic, more functional innervation. LEVEL OF EVIDENCE: NA Laryngoscope, 126:E337-E342, 2016.

Neurotrophin expression and laryngeal muscle pathophysiology following recurrent laryngeal nerve transection.

Laryngeal palsy often occurs as a result of recurrent laryngeal or vagal nerve injury during oncological surgery of the head and neck, affecting quality of life and increasing economic burden. Reinnervation following recurrent laryngeal nerve (RLN) injury is difficult despite development of techniques, such as neural anastomosis, nerve grafting and creation of a laryngeal muscle pedicle. In the present study, due to the limited availability of human nerve tissue for research, a rat model was used to investigate neurotrophin expression and laryngeal muscle pathophysiology in RLN injury. Twenty-five male Sprague-Dawley rats underwent right RLN transection with the excision of a 5-mm segment. Vocal fold movements, vocalization, histology and immunostaining were evaluated at different time-points (3, 6, 10 and 16 weeks). Although vocalization was restored, movement of the vocal fold failed to return to normal levels following RLN injury. The expression of brain­derived neurotrophic factor and glial cell line-derived neurotrophic factor differed in the thyroarytenoid (TA) and posterior cricoarytenoid muscles. The number of axons did not increase to baseline levels over time. Furthermore, normal muscle function was unlikely with spontaneous reinnervation. During regeneration following RLN injury, differences in the expression levels of neurotrophic factors may have resulted in preferential reinnervation of the TA muscles. Data from the present study indicated that neurotrophic factors may be applied for restoring the function of the laryngeal nerve following recurrent injury.

Is the External Branch of the Superior Laryngeal Nerve Dispensable in Thyroid Surgery?

BACKGROUND: There is growing evidence that the external branch of the superior laryngeal nerve (eSLN) participates in thyroarytenoid (TA) contraction, but little data quantify its role in vocal cord adduction. Injury to the eSLN, such as in thyroid surgery, is difficult to diagnose and likely underappreciated. It is the authors' belief that eSLN injury contributes to aspiration by depriving its contribution to the laryngeal plexus. The goal of this study was to measure the glottic closing force (GCF) from eSLN stimulation in a porcine model. METHODS: The recurrent laryngeal nerve (RLN) and eSLN were identified bilaterally in four porcine necks. Bilateral RLNs and eSLNs were stimulated simultaneously to obtain a control GCF using a pressure transducer placed in the glottis. Subsequently, bilateral eSLNs were stimulated and the GCF measured to quantify its percent contribution to the control value. RESULTS: Stimulation of the RLNs and the eSLNs each led to TA muscle contraction and a measureable GCF in all four porcine necks. The control GCF was 1000.1 mmHg, while the eSLN mediated CGF was 800 mmHg. The percentage GCF attributable to the eSLN was thus 800/1000 = 80%. CONCLUSIONS: Reflex glottic closure is one of the most important mechanisms for the prevention of aspiration during deglutition. The biomechanical quantification of glottic closure can be shown as the GCF. This study has shown that the eSLN contributes in a significant way to the GCF in a porcine model, a finding that has not been quantified to the best of the authors' knowledge. Therefore, greater focus should be placed on preserving this nerve in thyroid surgery.

Outcomes of Laryngeal Reinnervation for Unilateral Vocal Fold Paralysis in Children: Associations With Age and Time Since Injury.

OBJECTIVE: Outcomes of laryngeal reinnervation with ansa-cervicalis for unilateral vocal fold paralysis (UVFP) may be influenced by age of the patient and time interval between laryngeal nerve injury and reinnervation, suggesting less favorable outcomes in older patients and greater than 2-year time interval after injury. This study examines these issues in the pediatric population. METHOD: Review of prospectively collected data set of 35 children and adolescents (1-21 years) that underwent ansa-recurrent laryngeal nerve (RLN) laryngeal reinnervation for UVFP. RESULTS: The time from RLN injury to reinnervation averaged 5.0 years (range, 0.8-15.2 years). No correlation was found between age at reinnervation (r = 0.15) and patient- or parent-reported global percentage voice outcome or perceptual ratings. There was slight negative correlation in duration between RLN injury and reinnervation and voice outcomes (r = -0.31). Postoperative voice self/surrogate global percentage rating average was 80.5% (range, 50%-100%), and perceptual rating GRBAS sum score average was 2.9 (range, 0-7). CONCLUSION: In pediatric ansa-RLN reinnervation for UVFP, no correlation between age at surgery and postoperative outcome was found. Denervation duration showed slight negative correlation, similar to what has been reported in adults, though voice improvement was seen in all patients.

Thyroid surgery and the usefulness of intraoperative neuromonitoring, a single center study.

UNLABELLED: Purpose/Aim of study: To compare the use of intraoperative neuromonitoring (IONM) versus visualization of the recurrent laryngeal nerve (RLN) alone in thyroid surgery with regard to incidence in postoperative RLN injury and operation time. MATERIALS AND METHODS: This retrospective cohort study was performed in the Amphia Hospital, the Netherlands. All thyroid gland operations were collected from September 2009 to October 2012. For each case we recorded the patient characteristics, indication for surgery, intraoperative data, complications, results of pathological evaluation, and consultation of a ENT-surgeon. Research of current literature and statistical analysis was performed. RESULTS: In total, 147 patients were included and classified into an IONM and non-IONM group. Both groups were similar in demographical aspects and indications for surgery. In total, we had 170 nerves at risk (NAR). In both groups, there were 85 (50%) NAR. Overall injury to the RLN was 6%. A statistical significant decrease of permanent RLN injuries was noticed in the IONM group compared to the non-IONM group (n = 0 vs n = 6; p = .044). In transient RLN injury, no difference was noticed (n = 2 vs n = 2). Operation time with or without IONM was not significantly different for hemithyroidectomies, neither for total thyroidectomies. CONCLUSION: IONM is a useful tool as an adjunct in thyroid surgery to prevent RLN injury. A statistical significant decrease in permanent RLN injury with the use of IONM was found, but it did not significantly decrease time of operation.

Superior laryngeal nerve injury: effects, clinical findings, prognosis, and management options.

PURPOSE OF REVIEW: The superior laryngeal nerve (SLN) provides motor innervation to the cricothyroid muscle. However, the functions of this muscle and the anatomic variations of the nerve that supplies it are not fully understood. SLN paresis and paralysis (SLNp) is difficult to diagnose because of a lack of consistent laryngeal findings, and its effects on the voice likely go beyond simple pitch elevation control. RECENT FINDINGS: Although SLNp has traditionally been thought to lead to voice pitch limitation, recent research findings reveal multiple roles for this nerve in voice and speech. Cricothyroid muscles are the primary controls of fundamental frequency of voice. SLNp can lead to significant contraction of pitch range, vocal fold vibratory phase asymmetry, and acoustic aperiodicity, thus leading to an overall poor vocal quality. In addition, cricothyroid muscles may also play a role in pitch lowering and shifting from voiced to unvoiced sounds during speech. SUMMARY: Subtle signs, symptoms, and diagnostic findings associated with SLNp make this disorder difficult to characterize clinically. Lack of treatment methodologies to restore the dynamic action of the cricothyroid muscles poses difficulties in treating patients with this condition. A more thorough understanding of the effects of SLNp will improve diagnosis and treatment.

Transplantation of olfactory ensheathing cells to evaluate functional recovery after peripheral nerve injury.

Olfactory ensheathing cells (OECs) are neural crest cells which allow growth and regrowth of the primary olfactory neurons. Indeed, the primary olfactory system is characterized by its ability to give rise to new neurons even in adult animals. This particular ability is partly due to the presence of OECs which create a favorable microenvironment for neurogenesis. This property of OECs has been used for cellular transplantation such as in spinal cord injury models. Although the peripheral nervous system has a greater capacity to regenerate after nerve injury than the central nervous system, complete sections induce misrouting during axonal regrowth in particular after facial of laryngeal nerve transection. Specifically, full sectioning of the recurrent laryngeal nerve (RLN) induces aberrant axonal regrowth resulting in synkinesis of the vocal cords. In this specific model, we showed that OECs transplantation efficiently increases axonal regrowth. OECs are constituted of several subpopulations present in both the olfactory mucosa (OM-OECs) and the olfactory bulbs (OB-OECs). We present here a model of cellular transplantation based on the use of these different subpopulations of OECs in a RLN injury model. Using this paradigm, primary cultures of OB-OECs and OM-OECs were transplanted in Matrigel after section and anastomosis of the RLN. Two months after surgery, we evaluated transplanted animals by complementary analyses based on videolaryngoscopy, electromyography (EMG), and histological studies. First, videolaryngoscopy allowed us to evaluate laryngeal functions, in particular muscular cocontractions phenomena. Then, EMG analyses demonstrated richness and synchronization of muscular activities. Finally, histological studies based on toluidine blue staining allowed the quantification of the number and profile of myelinated fibers. All together, we describe here how to isolate, culture, identify and transplant OECs from OM and OB after RLN section-anastomosis and how to evaluate and analyze the efficiency of these transplanted cells on axonal regrowth and laryngeal functions.

Intraoperative neural monitoring in thyroid cancer surgery.

BACKGROUND: Intraoperative neural monitoring (IONM) has increasingly garnered the attention of the surgeons performing thyroid and parathyroid surgery around the world. Current studies suggest a majority of general and head and neck surgeons utilize neural monitoring in their thyroid surgical case load in both the US and Germany. PURPOSE: We aim to present an up-to-date review of the application of IONM specifically focusing on its utility in thyroid cancer surgery. Neural monitoring is discussed particularly as it relates to neural prognosis, the issues of staged thyroid surgery for thyroid cancer, and new horizons in the monitoring of the superior laryngeal nerve (SLN) and prevention of neural injury through continuous vagal neural monitoring. CONCLUSION: IONM, as it relates to thyroid surgery, has obtained a widespread acceptance as an adjunct to the gold standard of visual nerve identification. The value of IONM in prognosticating neural function and in intraoperative decision making regarding proceeding to bilateral surgery is also well-known. Initial data on recent extensions of IONM in the form of SLN monitoring and continuous vagal nerve monitoring are promising. Continuous vagal nerve monitoring expands the utility of IONM by providing real-time electrophysiological information, allowing surgeons to take a corrective action in impending neural injury.

Unilateral superior laryngeal nerve lesion in an animal model of dysphagia and its effect on sucking and swallowing.

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.