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Convergence of afferent inputs from the chorda tympani, lingual-tonsillar and pharyngeal branches of the glossopharyngeal nerve, and superior laryngeal nerve on the neurons in the insular cortex in rats.

The responses of single neurons in the insular cortex to electrical stimulation of the chorda tympani (CT), lingual-tonsillar branch of the glossopharyngeal (LT-IXth) nerve, pharyngeal branch of the glossopharyngeal (PH-IXth) nerve, and superior laryngeal (SL) nerve were recorded in anaesthetized and paralyzed rats. Ninety-four neurons responding to stimulation of at least one of the four nerves were identified from the insular cortex. Most of the neurons were located in the posterior portion of the insular cortex; the mean location was 0.8 mm anterior to the anterior edge of the joining of the anterior commissure (AC) and was 1.4 mm dorsal to the rhinal fissure (RF). Of the 94 neurons, 84 (89%) received convergent inputs from two or more nerves, and the remaining 10 (11%) received inputs from one nerve. The neurons responding to the CT stimulation were distributed more anteriorly than those responding to other three nerves in the anterior-posterior dimension. Our results indicate that the neurons recorded mainly from the posterior portion of the insular cortex receive convergent inputs from the oropharyngolaryngeal regions.

Animals↗

Paraganglia of the human recurrent laryngeal nerve.

Recurrent laryngeal nerves (RLNs) from human autopsy material were collected and prepared for light microscopy. Within five of eight investigated RLNs, paraganglia-like organs were found, the mean cross-sectional area of which was estimated to be 0.03 mm2. These organs were composed of cells resembling the type I and type II cells of the carotid body. The possible function of laryngeal nerve paraganglia is discussed.

Cell Nucleolus↗

[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.

Electric Stimulation↗

Recurrent laryngeal nerve palsy after thyroidectomy with routine identification of the recurrent laryngeal nerve.

BACKGROUND: The aim of this study was to assess the risk of recurrent laryngeal nerve palsy (RLNP) after thyroidectomy with routine identification of the recurrent laryngeal nerve (RLN) during the operation. METHODS: The present study was confined to 521 patients, 348 total lobectomies and 178 total thyroidectomies, treated by the same surgeon. Temporary and permanent RLNP rates were analyzed for patient groups with stratification of primary operation for benign thyroid disease, thyroid cancer, Graves' disease, and reoperation. Measurement of the RLNP rate was based on the number of nerves at risk. Twenty-six RLNs in 20 thyroid cancer patients with intentional sacrifice were excluded from analysis. RESULTS: Forty RLNs (40 patients) developed postoperative RLNP. Complete recovery of RLN function was documented for 35 of the 37 patients (94.6%) whose RLN integrity had been ensured intraoperatively. Recovery from temporary RLNP ranged from 3 days to 4 months (mean, 30.7 days). Overall incidence of temporary and permanent RLNP was 5.1% and 0.9%, respectively. The rates of temporary/permanent RLNP were 4.0/0.2%, 2.0/0.7%, 12.0/1.1%, and 10.8/8.1% for groups classified according to benign thyroid disease, thyroid cancer, Graves' disease, and reoperation, respectively. CONCLUSIONS: Operations for thyroid cancer, Graves' disease, and recurrent goiter demonstrated significantly higher RLNP rates. Invasion of RLN was identified in 19.4% of patients with thyroid cancer. Postoperatively, the RLN recovered in most of the patients without documented nerve damage during the operation. Total lobectomy with routine RLN identification is recommended as a basic procedure in thyroid operations.

Adolescent↗

Internodal segments in human laryngeal nerves.

The laryngeal nerves of a recently deceased patient were examined in order to determine whether the prenatal elongation of the recurrent nerves (especially of the left) is accompanied by significant elongation of internodal segments among their myelinated fibres. No evidence was found to support this notion. In the nerve roots of the cauda equina, internodal elongation is known to accompany ascent of the spinal cord during fetal life. The difference in behaviour in the two cases seems to lie in the fact that the laryngeal nerves reach their final positions before myelination commences, whereas the spinal nerve roots elongate later, at a time when Schwann cell multiplication has largely ceased.

Humans↗

Effect of recurrent laryngeal nerve section on the laryngeal muscles of adult rabbits.

OBJECTIVE: To examine the effect of recurrent laryngeal nerve section on myonuclear addition and myofiber remodeling in adult rabbit laryngeal muscles. STUDY DESIGN AND SETTING: Unilateral section of the recurrent laryngeal nerve was performed on adult rabbits. Rabbits were labeled with bromodeoxyuridine, euthanized, and the laryngeal muscles were examined for bromodeoxyuridine (brdU) and neonatal myosin heavy chain (MyHC) expression. RESULTS: One week after nerve section, brdU-positive myonuclei were significantly increased on the denervated and contralateral sides. Neonatal MyHC expression significantly increased. By 24 weeks, the upregulation of myonuclear addition returned to control levels. CONCLUSION: Laryngeal muscle denervation results in significant upregulation of myonuclear addition. Denervation also resulted in a significant upregulation of neonatal MyHC expression. SIGNIFICANCE: Laryngeal muscles can be successfully reinnervated after long periods of denervation. This significant and maintained increase in myonuclear addition may contribute to the ability of laryngeal muscles to survive for extended periods following interruption of the recurrent laryngeal nerve.

Animals↗

Central connections of the lingual-tonsillar branch of the glossopharyngeal nerve and the superior laryngeal nerve in lamb.

Afferent and efferent central connections of the lingual-tonsillar branch of the glossopharyngeal nerve (LT-IX) and the superior laryngeal nerve (SLN) in the lamb were traced with horseradish peroxidase (HRP) histochemistry. After entering the brainstem, most LT-IX and SLN afferent fibers turned caudally in the solitary tract (ST). Some afferent fibers of LT-IX terminated in the medial nucleus of the solitary tract slightly caudal to their level of entry. The remaining fibers projected to the dorsolateral, ventrolateral, and interstitial areas of the nucleus of the solitary tract (NST) at the level of the area postrema. Superior laryngeal nerve afferent fibers terminated extensively in the medial and ventral NST at levels near the rostral pole of the area postrema. Further caudal, near the level of obex, SLN afferent terminations were concentrated in the region ventrolateral to the ST and in the interstitial NST. The caudal extent of LT-IX and the rostral extent of SLN terminals projected to similar levels of the NST, but only a relatively small proportion of the total projections overlapped. Lingual-tonsillar and SLN fibers also coursed rostrally to terminate in the caudal pons within and medial to the dorsomedial principal sensory trigeminal nucleus. Other labeled afferent fibers traveled caudally in the dorsal spinal trigeminal tract to terminate in the dorsal two-thirds of the spinal trigeminal nucleus at the level of obex. Large numbers of labeled cells with fibers in the LT-IX or SLN were located in the ipsilateral rostral nucleus ambiguus and surrounding reticular formation. Fewer labeled cells were observed in the inferior salivatory nucleus following HRP application to either the LT-IX or SLN. The LT-IX and SLN projections to areas of the NST associated with upper airway functions, like swallowing and respiration, suggest an important role for these two nerves in the initiation and control of airway reflexes.

Animals↗

Laryngeal behavior in unilateral superior laryngeal nerve paralysis.

Laryngeal behavior in unilateral superior laryngeal nerve (SLN) paralysis was investigated in animal models and clinical cases. The occurrence of an oblique glottis caused by rotation of the posterior glottis to the paralytic side was the main focus of this study. The animal model study employed live dogs. When the SLN on one side was sectioned, spontaneous phonation did not cause a significantly oblique glottis. When the unaffected SLN was electrically stimulated during spontaneous phonation, an oblique glottis occurred. When the SLN was unilaterally stimulated during spontaneous phonation with both SLNs sectioned, a markedly oblique glottis occurred. In the clinical study, larynges of 17 patients with SLN paralysis were examined during a test task in which a low-pitched phonation was followed by a high-pitched phonation. The purpose of this task was to activate the unaffected cricothyroid muscle during the test phonation. Five patients could not perform the test task. The glottis obviously rotated in 9 patients, whereas no significant rotation of the glottis occurred in 3. One of the latter 3 had an incomplete paralysis, and the other 2 had marked scarring around the laryngeal framework. We conclude that a unilateral SLN paralysis causes a rotation of the posterior glottis to the paralytic side when the unaffected cricothyroid muscle is markedly activated. The test consisting of low-pitched phonation followed by high-pitched phonation is a relatively simple and accurate diagnostic procedure for unilateral SLN paralysis.

Adult↗

Intraoperative electromyogram monitoring of the recurrent laryngeal nerve: experience with an intralaryngeal surface electrode. A method to reduce the risk of recurrent laryngeal nerve injury during thyroid surgery.

INTRODUCTION: A clinical method to localize the recurrent laryngeal nerve intraoperatively in order to minimize the risk of accidental injury is presented. METHODS AND RESULTS: By means of an electrode, the nerve was stimulated by a pulsed contact current. The resulting muscle potential was detected using an electrode placed in the larynx. We applied this technique during the time period between 1 January 1997 and 31 December 1998. In 96 cases of primary thyroid resection, the recurrent nerve was identified 167 times. The patients were operated on for nodular thyroid (n=85), Grave's disease (n=9) and malignant papillary goiter (n=2). Retrospectively, the rate of intraoperative nerve injury, equivalent to the rate of postoperative transient and permanent nerve palsy, was 1.04% in the 96 patients and 0.60% with respect to the 167 nerves at risk. The rate of failure of the method was 7.29%.

Electrodes, Implanted↗

Importance of pre-operative recognition of the nonrecurrent laryngeal nerve.

The nonrecurrent laryngeal nerve is vulnerable during thyroid surgery. Pre-operative recognition of this nerve allows surgeons to avoid injuring the nerve. This anomaly depends upon the aortic arch anomaly and, therefore, in some cases, surgeons are able to predict the presence of this nerve pre-operatively by chest X-ray or barium swallow. Two patients with nonrecurrent laryngeal nerve are reported, one of whom, a 48-year-old man, had an abnormal shadow of the aortic arch, which led to confirmation of a right aberrant subclavian artery. Barium swallow plays a decisive role in the diagnosis of nonrecurrent laryngeal nerve, and this test is mandatory in patients who complain of difficulty in swallowing.

Abnormalities, Multiple↗

Update: ansa cervicalis to recurrent laryngeal nerve anastomosis for unilateral laryngeal paralysis.

Twenty cases of unilateral laryngeal paralysis are reported. Satisfactory follow-up intervals and data (videostroboscopy and glottographic analysis) were available on 12 patients. The excellent to normal phonatory quality achieved in many of these patients indicates that the ansa cervicalis to recurrent laryngeal nerve anastomosis is the procedure of choice in selected patients with unilateral vocal cord paralysis. Excellent medialization of the paralyzed cord, as well as correction of arytenoid malposition and thyroarytenoid muscle atrophy appear to explain the technique's success, since the reinnervated cord neither abducts nor adducts. We feel that this technique is the procedure of choice in younger patients, or those who use their voices professionally, since the phonatory quality achieved is superior to Teflon injection or Isshiki thyroplasty, and the technique is reversible.

Humans↗

Benign anatomical mistakes: the correct anatomical term for the recurrent laryngeal nerve.

The term recurrent laryngeal nerve has been adopted by Nomina Anatomica (1989) and Terminologia Anatomica (1998) to describe this vagus branch from its origin, its turn dorsally around the subclavian artery and the aortic arch, and its cranial pathway until it reaches its terminal organs in the neck. However, there is still much confusion, and either the terms inferior and recurrent laryngeal nerve are used interchangeably or inferior laryngeal nerve is considered the terminal branch of the recurrent laryngeal nerve. We hereby feel that it is necessary to reassess the term and we propose the term inferior laryngeal nerve for the entire nerve under consideration, from its origin from the vagus nerve to its destinations, including tracheal, esophageal, and pharyngeal branches. If the term superior laryngeal nerve is a given, standard and accepted term in the anatomical terminology, then logically the term inferior laryngeal nerve should also be accepted, as opposed to it. Of course the upward travel of the inferior laryngeal nerve is "recurrent". When nonrecurrence is encountered together with an arteria lusoria, a retroesophageal right subclavian artery or a right aortic arch, we consider that the term nonrecurrent inferior laryngeal nerve should be used to describe the deviation from the normal.

Humans↗

The responses of superior laryngeal nerve afferent fibres to laryngeal airway CO2 concentration in the anaesthetized cat.

In anaesthetized cats, the isolated, in situ, larynx was subjected to a simulated respiratory cycle and the responses of fifty-six superior laryngeal nerve (SLN) afferent fibres to respiration-related stimuli were examined during changes in the fractional CO2 concentration of the laryngeal airway (Faw, CO2). Sensory SLN fibres which displayed low rates of discharge when the larynx was unventilated (quiescent fibres) and which responded to negative laryngeal airway pressure were excited by elevations in Faw, CO2 whereas quiescent fibres responsive to positive laryngeal pressure were inhibited by the same procedure. We propose that changes in airway CO2 levels may play a role in maintaining upper airway patency, especially during sleep.

Anesthesia↗

Recurrent laryngeal nerve injury with the laryngeal mask.

We report a case of recurrent laryngeal nerve injury after anesthesia with the LMA and review the published cases of major pharyngolaryngeal morbidity. Prevention of this and other pharyngolaryngeal injuries probably depends on the skilled application of the correct insertion technique and the use of low intracuff pressures and volumes.

Aged↗

[Nerve exploration and decompression for traumatic recurrent laryngeal nerve injuries induced by thyroid gland surgery].

OBJECTIVE: To show the findings of recurrent laryngeal nerve injury exploration and find out therapeutic effects, indications and timing of nerve decompression for traumatic recurrent laryngeal nerve injury induced by thyroid gland surgery. METHODS: In this study there were 87 patients with recurrent laryngeal nerve injury, including 65 for nerve exploration and 22 for nonsurgical treatment. During nerve exploration, the types, severity of laryngeal nerve injuries and laryngeal muscular mass were studied. Nerve decompression was performed in these 14 patients whose compressing sutures or compression due to cicatricial hypertrophy were received nerve decompression. RESULTS: Injuries caused by thyroid gland operations mostly are of suture ligation (43%) and nerve severance (48%); simple scar compression was found only in 6 cases (9%). Atrophy of the laryngeal muscles was not very serious in patients with a course less than 6 months. In 10 patients with a course less than three months, nerve decompression restored normal functional abductor and abductor motion of the vocal cord in 9 patients and had no effects in one. Although functional motion of vocal cord was not seen in one case with a course less than 3 months and 4 cases between 3 and 5 months, the mass and tension of the reinnervated vocal cord became much the same as the contralateral normal vocal cord, thus resuming symmetric vibration of the vocal cords and physiological phonation. Although nonsurgical treatment improved severe hoarseness, it didn't restore normal functional motion of the vocal cord and normal voice. CONCLUSIONS: Nerve exploration showed a primary rule for recurrent laryngeal nerve injury induced by thyroid gland surgery. Early and mid-stage recurrent laryngeal nerve exploration and decompression may restore normal motion of the glottis, and it suggested laryngeal delayed reinnervation may help patients with a course more than 6 months.

Adult↗