Electromyographic findings in recurrent laryngeal nerve reinnervation

Abductor, adductor, and combined reinnervation procedures have been explored with variable success rates. We describe the experience of a tertiary care center with adductor reinnervation procedures, including preoperative and postoperative videostroboscopy and electromyography (EMG) findings. A retrospective chart review was performed from 1997 to 2001 that included 9 patients. Preoperative and postoperative voice comparison was performed by 3 blinded speech pathologists. Clinical comparisons of videostroboscopy findings for vocal fold bulk, tone, position, presence of gap, and movement are elucidated. The preoperative and postoperative EMG findings are described. In all patients, preoperative EMG revealed a dense, complete denervation of the affected recurrent laryngeal nerve. No movement was noted on videostroboscopy with persistent glottic gap. Reinnervation involved a nerve-muscle pedicle or a direct neurorrhaphy of the ansa cervicalis to the recurrent laryngeal nerve. Voice improvement was noted between 60 days and 3 months after reinnervation. Four postoperative EMG studies were performed. An early postoperative EMG study at 5 months revealed activation of the lateral cricoarytenoid muscle and thyroarytenoid muscle with head-lift. Videostroboscopy showed excellent near-midline static positioning of the vocal fold. Late EMG studies, performed 12 to 16 months after reinnervation, revealed "learning" of these muscles, with new activation on "eee" phonation. We conclude that recurrent laryngeal nerve reinnervation procedures belong in the armamentarium of the laryngologist for the treatment of vocal fold paralysis. The EMG findings reported in this study suggest that ongoing reinnervation allows for activation with phonation in matured neuronal anastomoses. Overall, this procedure results in excellent patient acceptance and near-normal vocal quality.     

单侧喉返神经损伤神经修复术式探讨

目的　探讨 5种神经修复术治疗单侧喉返神经损伤声带麻痹的疗效。方法　 1993年 1月～ 2 0 0 1年 4月治疗外伤性单侧喉返神经损伤声带麻痹 38例 ,病程从损伤即刻至 2年不等。资料完整者 35例 ,其中行神经减压术 8例、颈襻主支喉返神经吻合术 16例、喉返神经端端吻合术 6例、颈襻神经肌蒂埋植术 3例、颈襻神经植入术 2例。手术前后喉镜、嗓音声学参数、肌电图检查等评价手术效果。结果　病程 4个月内神经减压 5例恢复了正常的声带内收及外展功能 ,4个月以内 1例、以上2例及颈襻主支吻合组、喉返神经端端吻合组则未恢复声带运动。但上述 3种术式均能使喉内收肌获有效的再神经支配 ,满意地恢复声带的肌张力、肌体积、声带振动对称性及正常黏膜波 ,声门闭合良好 ,嗓音恢复正常。颈襻神经肌蒂埋植术及颈襻神经植入术均能改善声嘶 ,但无恢复正常病例。结论　①单侧喉返神经损伤神经修复治疗以神经减压效果最佳 ;②颈襻主支吻合术、喉返神经端端吻合术也能有效地恢复喉的发音功能 ;③喉神经修复术式选择应根据病程、神经损伤程度、类型而定     

Spontaneous laryngeal reinnervation after recurrent laryngeal or vagus nerve injury

OBJECTIVES: The status of innervation in patients with laryngeal paralysis is somewhat controversial. Electromyographic activity has been frequently documented in the laryngeal muscles of patients with laryngeal paralysis, and animal experiments report a strong propensity for reinnervation after laryngeal nerve injury. However, a study of intraoperative electromyography performed in patients during reinnervation surgery failed to document activity with stimulation of the recurrent laryngeal nerve (RLN). Noting the long-observed differences in the symptoms of patients with vagus nerve injury and those with RLN injury, I hypothesized that reinnervation is influenced by the site of nerve injury. METHODS: Cats were sacrificed at various intervals after resection of 1 cm of either the RLN or the vagus nerve, without any attempt to repair the nerve. RESULTS: Four months after RLN resection, distal nerve biopsy revealed unmyelinated axons scattered through fibrous tissue. By 6 months, myelinated axons were organized, and electromyographic and histologic examination showed preferential reinnervation of the thyroarytenoid muscle. After vagotomy, the RLN was fibrotic and no axons were present. Both the thyroarytenoid and posterior cricoarytenoid muscles were fibrotic and had no electromyographic activity. CONCLUSIONS: The results confirm the strong propensity for laryngeal reinnervation after RLN injury, but not after vagus nerve injury. Preferential reinnervation of adductor muscles may account for a medial position of the paralyzed vocal fold.     

Laryngeal reinnervation for unilateral traumatic recurrent laryngeal nerve injuries]

OBJECTIVE: To investigate 5 procedures of laryngeal reinnervation for unilateral vocal cord paralysis induced by traumatic recurrent laryngeal nerve injury. METHODS: 35 cases were selected for our study, all patients had unilateral recurrent laryngeal nerve injury, including 8 for nerve decompression, 6 for end to end anastomosis of recurrent laryngeal nerve, 16 for main branch of ansa cervicalis anastomosis to recurrent laryngeal nerve, 3 for nerve muscular pedicle and 2 for nerve implantation. All cases have been subjected to preoperative and postoperative voice recording, acoustic analysis, videolaryngoscopy, strobscopy and electromyography. RESULTS: It is found the adductory and abductory motion of the vocal cord restored in 5 cases with less than 4 months course who received nerve decompression. Although functional motion of vocal cord was not seen in two patients who received nerve decompression with a course longer than 4 months and one less than 4 months, and in all cases who received ansa cervicalis anastomosis and end to end anastomosis of recurrent laryngeal nerve, these procedures resulted in medialization of vocal cord and the mass and tension of the reinnervated vocal cord may become much the same as the contralateral normal vocal cord, thus resuming symmetric vibration of the vocal cords and physiological phonation. Nerve muscular pedicle technique and nerve implantation enabled adductory muscles to be reinnervated, thus improving severe hoarseness, but they didn't restore normal voice. CONCLUSIONS: (1) Nerve decompression seems to be the best procedure in laryngeal reinnervation; (2) Main branch of ansa cervicalis technique raises satisfactory reinnervation of adductor muscles; (3) Selection of the laryngeal reinnervation protocols should depend on the course, severity and type of nerve injury.     

Surgical anatomy of the superior laryngeal nerve

The authors report on their anatomic findings in 42 surgical dissections of the superior laryngeal nerve. Better knowledge of this anatomy should enable a more conservative cervical surgery and help in attempts at nervous rehabilitation of laryngeal paralysis.     

The recurrent laryngeal nerve: Related vascular anatomy

This study was based on 34 recurrent laryngeal nerve dissections after arterial casting with red-colored latex. The aim was to provide specific information about the perineural microvasculature. This study established the following points: 1. a great anatomic variability does exist; 2. the laryngeal nerve is usually in relation to the posterior branch of the inferior thyroid artery; and 3. this vascular branch is sometimes replaced with a vascular network. In all cases, this microvascularization must be preserved during thyroid surgery. Key Words: Recurrent laryngeal nerve, anatomy, inferior thyroid artery.     

A novel modification of the ansa to recurrent laryngeal nerve reinnervation procedure for young children

Vocal ford paralysis is a condition often seen in otolaryngologic adult and pediatric clinics. We report a case we believe to be the youngest child to undergo ansa cervicalis (ansa) to recurrent laryngeal nerve (RLN) reinnervation for unilateral vocal fold paralysis. We have included the preoperative and postoperative videostroboscopic and acoustic findings. The acoustic data shows improvement and is consistent with the patient's improved voice quality. Most notably the patient's voice quality is less raspy and his volume has improved while subjectively requiring less effort.     

Aberrant recurrent laryngeal nerve reinnervation as a cause of stridor and laryngospasm

Unilateral vocal fold paralysis rarely presents with symptoms of stridor, laryngospasm, and dyspnea. Abnormal reinnervation of abductor nerve branches into adductor fibers may be one cause. Four patients have been positively identified by laryngeal electromyography. Two patients presented after thyroid surgery for thyroid neoplasm. One presented after cervical disk surgery. One patient presented after herpes simplex infection with multiple cranial nerve involvement. All patients had new onset of dyspnea with exertion many months after the recurrent nerve injury. Fiberoptic laryngoscopy showed the affected vocal fold to be immobile. However, with hyperventilation and deep inspiration, there was paradoxical adductor motion of the paretic vocal fold. Laryngeal electromyography showed evidence of reduced but intact voluntary motor units in the thyroarytenoid muscle. These motor units fired on inspiration and not on phonation. This pattern was not seen on the normal side. These findings are consistent with paradoxical innervation and/or synkinesis. Each patient was managed by Botox injection into the adductor muscle. Periodic reinjections may be necessary to manage the condition.     

Surgical anatomy of the extralaryngeal aspect of the superior laryngeal nerve

OBJECTIVES: To describe the topography of the superior laryngeal nerve (SLN) and to evaluate the influence of gender, ethnicity, side of the neck, and individual height on the topography of the SLN. DESIGN: Anatomical study of human cadavers. SUBJECTS: Fifty fresh human cadavers (19 female subjects and 31 male subjects; age range, 22-89 years; mean age, 61 years) were randomly selected for this study. The subjects were divided into nonwhite (n = 18) and white (n = 32) ethnic groups. The t test and linear regression were used for statistical analysis of data. RESULTS: All SLNs emerged medially to the vagus nerve. The SLNs mostly divided into internal (ibSLN) and external (ebSLN) branches distally from their origin (94%). The mean +/- SE length of the SLN trunk was 16.7 +/- 0.9 mm and was affected by gender (P =.01) but not ethnicity (P =.57), side of the neck (P =.96), or individual height (R2 = 0.01; P =.33). The length of the ibSLN reached 44.9 +/- 1.0 mm and was unaffected by gender (P =.91), ethnicity (P =.24), side (P =.40), or height (R2<0.01; P =.71). The length of the ebSLN measured 62.6 +/- 1.2 mm and was unaffected by gender (P =.69), ethnicity (P =.42), side (P =.26), or height (R2<0.01; P =.85). The mean +/- SE angle between the ibSLN and the tracheoesophageal sulcus was 49 degrees +/- 1 degrees and was unaffected by gender (P =.35), ethnicity (P =.11), side (P =.26), or height (R2<0.01; P =.96). Only 1 subject demonstrated a bilateral anatomical variation of the ibSLN close to its entrance into the thyrohyoid membrane. CONCLUSIONS: The topography of the SLN has a few anatomical variations and is unaffected by gender, ethnicity, side of the neck, and individual height, except that the SLN is longer in males than in females. These findings are important in that they can help in the prevention of SLN injuries during operations such as laryngectomy and neck dissection, as well as in the planning of laryngeal reinnervation and transplantation.     

Vagal stimulation and laryngeal electromyography for recurrent laryngeal reinnervation in children

Ansa-to-recurrent laryngeal nerve (ANSA-RLN) reinnervation procedures are now often first-line treatments for some children with unilateral vocal fold immobility. Although many describe that children with prolonged denervation and true vocal fold atrophy should not undergo this procedure, there has been no gold-standard means of identifying true denervation. Here, we describe a novel technique using evoked vagal electromyography to predict degree of chronic nerve injury prior to recurrent laryngeal nerve reinnervation in children. This is a simple, readily available technique that may play an important role in predicting likelihood of success with pediatric ANSA-RLN reinnervation. Laryngoscope, 130:747–751, 2020     

Hypoglossal nerve transfer for laryngeal reinnervation: a preliminary study

The hypoglossal nerve is a logical donor nerve for hemilaryngeal reinnervation because 1) its activity coincides with normal laryngeal adduction during speech and deglutition; 2) it is a large nerve with many axons; and 3) donor site morbidity is low. This method of laryngeal reinnervation has not been previously reported. Previous studies using the ansa cervicalis for reinnervation have failed to show spontaneous activity. Hypoglossal-to-recurrent laryngeal nerve anastomosis was performed on a series of 5 dogs. The vocal folds were viewed monthly, with the animals awake, by infraglottic examination through a permanent tracheostomy. One dog failed due to technical error. The remaining 4 dogs began to exhibit spontaneous vocal fold adduction within 2 to 4 months. Vocal fold motion was synchronous with spontaneous tongue motion. Complete glottic closure was seen during swallowing at 3 to 5 months. Intraglottic pressure measurements following reinnervation were normal. Hypoglossal nerve transfer appears to be capable of providing functional adduction to the paralyzed hemilarynx. The potential advantages and disadvantages of this new technique are discussed.     

Intraoperative neurophysiological monitoring (IONM) of the recurrent laryngeal nerve and microdissection. Surgical techniques for decreasing the risk of recurrent laryngeal nerve paralysis

BACKGROUND: Frequently numerous recurrent laryngeal nerve injuries occur after operations on the thyroid glands. Compared with postoperative permanent hypocalcemia, unilateral and especially double-side recurrent paresis pose serious complication. As early as 1938 specialists [1] pleaded for a routine visualisation of the nervus recurrens in operations of the thyroid gland, to reduce the risk of permanently recurring paresis. In controversial discussions of the matter specialists have opted for a demonstration of the nerve also under medico-legal aspects. Implementing functionally-critical operational strategies requires the choice of an anatomically suitable operative procedure for the removal of morphological, functional and oncological changes, as well as the avoidance of complications. METHOD: Intra-operative Monitoring is highly recommendable as a neurophysiological method of supervision combined with microdissection to ensure the safe handling of recurrent laryngeal nerve. CONCLUSION: The rate of permanent paresis on the recurrent nerve can be lowered to less than 1 per cent when this is used as a routine procedure for all operations and the treatment of the thyroid gland diseases.     

Nimodipine improves reinnervation and neuromuscular function after injury to the recurrent laryngeal nerve in the rat

OBJECTIVES: Injury of the recurrent laryngeal nerve (RLN) is associated with a high degree of neuronal survival, but leads to various levels of vocal fold motion impairment or laryngeal synkinesis, which has been attributed to misdirected reinnervation of the target muscles in the larynx or aberrant, competing reinnervation from adjacent nerve fibers. The aim of the present study was to evaluate the impact of the regeneration-promoting agent nimodipine on reinnervation and neuromuscular function following RLN crush injury. METHODS: Sixty adult rats were randomized into nimodipine-treated or untreated groups and then underwent RLN crush injury. Reinnervation of the posterior cricoarytenoid muscle (PCA) was assessed by electrophysiological examination, retrograde tracing of lower motor neurons before and after injury, and quantification of neuromuscular junctions in the PCA muscle. RESULTS: At 6 weeks after injury, the nimodipine-treated animals showed significantly enhanced neuromuscular function and also demonstrated a higher number of motor neurons in the brain stem that had reinnervated the PCA, compared to the untreated animals. The somatotopic organization of ambiguus motor neurons innervating the larynx was similar before injury and after reinnervation. CONCLUSIONS: Nimodipine improves regeneration and neuromuscular function following RLN injury in the adult rat, and could be of use in future strategies following RLN injury.