Laryngeal Nerve Research Articles

Laryngeal and cranial nerve involvement after carotid endarterectomy

ConclusionsLaryngeal and/or cranial nerve involvement after CEA surgery is not a rare condition, occurring in almost half of operated subjects. However, in most cases the functional deficit is transient and does not need any particular form of treatment. In this study, specific rehabilitative procedures were needed in only a relatively small number of cases (9%). A routine ENT examination has also proved to be extremely useful for detecting slight functional deficits which may occur following CEA surgery, bearing in mind that possible permanent lesions may require a rehabilitative procedure.ObjectiveTo identify, by means of a careful otolaryngologic examination, the incidence and degree of cranial nerve deficit related to carotid endarterectomy (CEA), starting from the first postoperative days.Material and methodsA consecutive cohort of patients with symptomatic and asymptomatic carotid artery stenosis who underwent CEA was carefully followed on the basis of possible laryngeal and/or cranial nerve involvement. An ENT examination was carried out preoperatively (phase I) and at different times [3 (phase II) and 15 days (phase IIIa)] after surgery; in addition, patients with persisting neurological lesions were also checked 60 days after surgery (phase IIIb).ResultsIn 59% of the patients, isolated or associated forms of deficit were found. Only 17.5% of these deficits did not appear to be transient, but rehabilitative procedures for voice or swallowing impairments were only needed in 9% of them.

Autologous elastic cartilage for laryngoplasty: Histologic evaluation in a rabbit model

Problem: A wide range of materials have been used to achieve the medialization of the paralyzed vocal fold. Recently, medialization techniques using autologous cartilage have been described, but little information is available on cartilage integration and viability in this situation. Methods: In this prospective, experimental, controlled study, right vocal fold paralysis was surgically induced in 30 New Zealand rabbits. An autologous auricular cartilage transplant was inserted in the vocal fold in 15 animals. In the control group only the laryngeal nerve was sectioned. Each group was divided into 2 groups with a follow-up of 6 weeks and 6 months, respectively. Results: Histology studies revealed no inflammatory reaction against cartilage transplants. There were no differences in the transplant surfaces in the 6-week and 6-month groups. Results show tissue integration, and a low level of initial transplant resorption that stabilizes with time. Conclusion: Autologous auricular cartilage appears to be an appropriate material for type I thyroplasty procedures because of the low absorption rate. Significance: This study demonstrates that the autologous cartilage is an appropriate material for the medialization of paralyzed vocal cords. Support: Support: Supported in part by a grant from the National Health Ministry of Spain.

Distribution of pH regulators in the rat laryngeal nerve: the spatial relationship between Na +/HCO 3− cotransporters and Na +/H + exchanger type 3

We studied the distribution of Na +/HCO 3 − cotransporters (NBC) and Na +/H + exchanger type 3 (NHE3) in the laryngeal nerve by immunohistochemistry to elucidate the spatial relationship of pH regulation system in the peripheral nerves. The nervous components, i.e., the nerve cells in the nodose and local ganglia and nerve fibers, were immunoreactive for NBC. Glial components such as Schwann cells and satellite cells surrounding nerve fibers and nerve cell bodies were also immunoreactive for NBC in most cases, while the cells comprising the perineurium and endoneurium were immunoreactive for NHE3. These results suggest that NBC-dependent pH regulation systems are present in the laryngeal nerve. Whereas, NHE3 may regulate extracellular pH rather than intracellular pH. In conclusion, spatial relationship of NBC and NHE3 in the laryngeal nerve would be important for pH regulation. Perineural lymph may have key role for acid-induced modulation of axons and Schwann cells.

Percutaneous ethanol injection treatment of severe hyperparathyroidism in maintenance dialysis: Risks and benefits

Renal hyperparathyroidism is one of the main and serious complications that occur in chronic kidney disease and particularly during long-term maintenance dialysis. Several recent trials indicate that a high calcium phosphorus product is correlated with high cardiovascular morbidity and mortality and poor outcome. Thus, it is important to improve the control of hyperparathyroidism in chronic renal failure patients. Several methods have been reported for treating severe hyperparathyroidism resistant to medical therapy. Total parathyroidectomy and transplantation or excision of tumor is considered as the treatment of choice. More recently, interventional methods with percutaneous ethanol or calcitriol injection have been developed. These latter techniques have been reported as an alternative to surgical treatment for patients with high perioperative risk. We report the occurrence of laryngeal recurrent nerve palsy, vocal fold paralysis, and hemiplegia after a successful injection of ethanol in a left parathyroid adenoma in a maintenance hemodialysis patient and discuss the restrictions of the procedure and alternative treatments in view of the available studies.

Neuromonitoring Is Not a Standard Procedure in Thyroid Surgery

BACKGROUND: The main concern with postoperative results is the integrity of the voice. As there is no causal therapy for recurrent nerve paralysis, close attention has to be paid to the preservation of the laryngeal motor nerve. Neuromonitoring (NM) is a new technique for identifying the nerve in its anatomical position, but it has failed to lower the postoperative complication rate. METHODS: The data from the literature were compared. Many studies showed a rapid decrease in palsy rates by general nerve preparation, but the outcome was still influenced by various factors such as underlying disease and surgical radicality. Only one study did not show any difference in outcome with or without nerve identification. RESULTS: Even though there is an unequal composition of data sources, it is highly suggestive that surgical development that has focussed attention on nerve preservation has led to an improvement in postoperative outcome. In general, palsy rates with nerve preparation are below 1%. The same improvement is reported with the use of neuromonitoring. It seems that these effects are similar to those obtained by nerve preparation alone. Moreover, intra- and postoperative nerve function does not always correlate. No clear-cut advantage in the results achieved with NM can be stated. CONCLUSIONS: Besides the fact that considerable basic research has been done using NM, the data concerning improvement of nerve palsy rates do not necessitate its general use in routine thyroid surgery. Subtle operative technique and visualization of the structure are still mandatory. NM might help shorten the learning curve in identification exercises.

The distribution of ganglion cells in the posterior cricoarytenoid muscle of the normal adult rat. A light and electron microscopic study.

We employed by light and electron microscopy to examine the innervation of the posterior cricoarytenoid muscle of the adult rat. The laryngeal nerve was found to often bifurcate into two different bundles. One contained large myelinated (motor) nerve fibers, which were located along the frontal (ventral) muscle surface and entered the muscle at its middle portion to form neuromuscular contacts with individual muscle fibers. The other nerve bundle consisting of clustered ganglion cells (20-30 microm in diameter) and their associated nonmyelinated and small-sized myelinated nerve fibers were mainly found on the dorsal side of the muscle and often ran along the peripheral clefts or depressions of the muscle surface. The nerve bundle often extended side branches, which entered the muscle to be distributed among muscle fibers and near arterioles. Some ganglion cells are considered to enter the muscle, accompanied by branched nerves. Intramuscular ganglion cells and their associated nerve fibers examined by electron microscopy were similar in fine structure to perimuscular ganglion cells and their associated nerve fibers. Nerve fibers contained abundant clear synaptic vesicles which were cholinergic in nature, and often formed synapses with both neighboring axons and the cell body of the ganglion cells. These findings suggest that, in the rat posterior cricoarytenoid muscle, perimuscular and intramuscular ganglion cells exist and may be involved in innervating and contracting smooth muscle cells of the arterioles, thus regulating the blood flow or intravascular pressure.

Principles of surgery for thyroid carcinoma

Surgery is the initial therapy in thyroid carcinoma. The basic principles of surgical oncology in malignant epithelial tumors have their full improvement in thyroid carcinoma (TC). The surgery is performed on organ of tumor origin and regional lymphatic basins. The aim of surgery in thyroid carcinoma is to eradicate all tumor foci, cure the most number of patients, reduce recurrence and mortality rate, and provide good quality of life. There is no doubt between oncologists that the surgery for thyroid carcinoma has no alternative. The extent of surgery is matter of actual controversies. Surgery is the initial treatment for all differentiated, papillary and follicular, as well as medullary and even anaplastic thyroid carcinoma. It should be performed by well-trained surgeons. The surgery of thyroid gland is the surgery of laryngeal recurrent nerve and parathyroid glands. The extent of primary surgery should be dictated by stage of disease and prognostic factors. The quality of surgery and incidence of complications depends on surgeon's skill and experience. That is why the surgeon is factor of prognosis in treatment of patients with TC.

Total versus subtotal thyroidectomy: Arguments, approaches, and recommendations

Summary Arguments for routine total thyroidectomy or routine, less-than-total resection have been espoused for treatment of well-differentiated intrathyroidal carcinoma. Numerous reports in the literature support either approach. No prospective randomized studies have been performed, partly because of the indolent nature of the disease. Many reports are also complicated by the failure of the authors to divide patients into high-risk and low-risk groups and to categorize and evaluate fully the histologic types of the resected tumors. Good evidence exists to show that in the majority of cases of intrathyroidal, well-differentiated lesions, bilateral subtotal resection yields results that compare favorably with total thyroidectomy. Logically, at least, a total thyroidectomy would seem to be preferable because subtotal resection can be imprecise. Therefore, subtotal thyroidectomy can be recommended over total thyroidectomy, if only on the basis of comparison of complications. The type and rate of complications vary among surgeons. Each thyroid surgeon, therefore, must establish an individual complication rate. Total thyroidectomy in inexperienced hands is not recommended. We recommend, therefore, that total thyroidectomy be used selectively by surgeons who have the skill and experience necessary to make the decision intraoperatively. If, for example, during resection of the lobe that contains the primary tumor, the laryngeal nerves and parathyroid glands can be clearly identified and if there is minimal bleeding and trauma, the surgeon may proceed to side two to perform a total thyroidectomy. If the lesion is large, however, with distortion of anatomy, dissection may be difficult even for an experienced surgeon. Intracapsular parathyroids or undiscovered parathyroids on the side of initial resection should prompt the surgeon to perform a subtotal resection on side two. Under these circumstances, the surgeon should not feel that a total thyroidectomy justifies the increased risk. A unilateral resection, such as lobectomy plus isthmusectomy, can be performed with satisfactory long-term results in low-risk patients—that is, in those with small (less than 1.5 cm) unilateral intrathyroidal exposure and in those with no evidence of metastatic disease. Alternately, the AGES criteria of Hay et al 29 can be used to identify patients in low-or high-risk groups. If the decision to perform a bilateral resection is based on the previous criteria, we recommend that a total thyroidectomy be performed by an experienced surgeon only. During surgery, if there is any suggestion that the laryngeal nerves or parathyroid glands would be at increased risk if a total resection were performed, it may be necessary to revert to a subtotal procedure. This situation, and others like it, requires a level of judicious intraoperative surgical decision-making that comes only with experience.

Minimally invasive video-assisted approach for partial and total thyroidectomy: initial experience.

We report our initial experience with partial and total thyroidectomy using a video-assisted approach. The feasibility, safety, and potential benefits of this technique are examined. Between January and May 2000, 28 patients were select to undergo a thyroid lobectomy (n = 17) or total thyroidectomy (n = 11) by a video-assisted cervical approach. Patient selection was based on clinical examination and preoperative ultrasonography. The surgical procedures were conducted under general anesthesia through a minimal substernal skin incision. Frozen sections were examined peroperatively in all cases. The initial diagnosis was solitary nodule in 19 patients and multinodular goiter in 8 patients. One patient was treated for hyperthyroidism. The mean cranio-caudal axis and transverse diameter of the resected specimen were 4.9 +/- 0.9 and 2.7 +/- 0.5 cm, respectively, and the mean total lobar weight was 11.9 +/- 5.5 g. Conversion to conventional surgery was required in three patients (10.7%), due to local bleeding in all cases. The mean operative times were 150 +/- 8.2 and 102.5 +/- 17 min for total and partial thyroidectomy, respectively. The laryngeal nerve was identified in 94.8% of cases. The mean length of skin incision was 25.4 +/- 2 mm. There was one case of postoperative hypocalcemia and one case of postoperative hoarseness. One patient had a transient vocal cord palsy. The postoperative hospital stay was 1 day for 66.7% of patients. The pain intensity evaluation, performed on postoperative day 1 using the visual analogue scale (VAS) method, was 1.9 +/- 1.4. Video-assisted thyroidectomy is feasible, safe, and effective in selected cases. Benefits for the patients in terms of postoperative pain, hospital stay, and cosmesis still need to be assessed in a prospective trial comparing standard open and video-assisted approaches.

Laryngeal afferent inputs during vocalization in the cat.

To reveal the kind of information about the larynx which is transmitted to the central nervous system during vocalization, we studied discharge patterns of single fibers of the laryngeal afferent nerve during electrically induced vocalization in ketamine-anesthetized cats. Recorded fibers were classified into four types based on their discharge patterns. Type A fibers responded to vocal fold vibration during vocalization. Type B fibers increased their activity during vocalization without synchronization with vocal fold vibration. Type C fibers decreased their activity during vocalization. Type D fibers discharged only at the onset of vocal fold adduction and abduction. We discuss the functional properties of these afferents and the possibility that these afferent inputs participate in the feedback control of vocalization.

The augmentation of intrinsic laryngeal muscle activity by air-jet stimulation of the nasal cavity in decerebrate cats

The purpose of this study was to examine the functional roles of nasal afferents in modulating the activity of the intrinsic laryngeal muscles. The electromyographic activities of the intrinsic laryngeal muscles and major respiratory muscles were recorded in cats during nasal air-jet stimulation. The activities of brainstem respiratory neurons were also recorded to determine which neurons transmit nasal afferent signals to the intrinsic laryngeal motoneurons. These axonal projections were identified by antidromic activation evoked by stimulation to the spinal cord at C4 level and the laryngeal nerve. The length of the respiratory cycle was prolonged and the diaphragmatic activity was decreased during air-jet stimulation of the nasal cavity. In contrast, the activities of both the intrinsic laryngeal adductor and abductor muscles were increased. Examination of the laryngeal reflexes revealed increase in the activities of intrinsic laryngeal motoneurons during both respiratory phases. Most of the respiratory neurons recorded decreased their peak firing rate during air-jet stimulation, reflecting decreased diaphragmatic activity; however, the peak firing rate of the bulbospinal expiratory neurons in the portion of the ventral respiratory group caudal to the obex did not decrease during stimulation. These findings demonstrate the nasal air-jet stimulation decreases the activities of major inspiratory muscles in order to avoid inspiration of foreign bodies into the nasal cavity and augments the activities of intrinsic laryngeal muscles, enabling prompt elicitation of the laryngeal airway reflex. Our findings also suggest that the nasal afferents suppress the major inspiratory activities by way of brainstem inspiratory neurons, but that the activities of intrinsic laryngeal muscles are controled through undetermined pathway(s) other than the pathway through respiratory neurons.

Surgery of the Thyroid Gland

Since the year 1987 to 1996 all kinds of thyroid surgeries were performed at the ENT Department. Altogether 604 patients underwent 655 surgeries. Total lobectomy or total thyroidectomy represented the most common procedures. Due to a gentle surgical technique, which we call "preparation", good results were achieved in the morbidity of laryngeal recurrent nerve (permanent palsy in 0.6%), and in perioperative or postoperative bleeding (0.3% of wound revisions, 0.5% of blood transfusions). Postoperative hypoparythyroidism was found in 4.7% patients. There is no correlation between postoperative hoarseness and laryngeal recurrent nerve palsy. Laryngeal endoscopy immediately after surgery is the most valuable diagnostic procedure.

Convergence of oropharyngolaryngeal, baroreceptor and chemoreceptor afferents onto insular cortex neurons in rats.

Forty-two neurons that responded to electrical stimulation of at least one of four nerves, the chorda tympani (CT), the lingual-tonsillar branch of the glossopharyngeal (LT-IXth) nerve, the pharyngeal branch of the glossopharyngeal (PH-IXth) nerve and the superior laryngeal (SL) nerve, were identified from the insular cortex by using glass microelectrodes in paralysed and anesthetized rats. Four, 42, 41 and 40 neurons responded to the CT, LT-IXth, PH-IXth and SL nerve stimulation respectively. Of these 42 neurons, most (37/42, 88.1%) responded to three nerves (the LT-IXth, PH-IXth and SL), two (4.8%) responded to two nerves and the remaining three (7.1%) responded to all four nerves. No neurons responded to one specific stimulus. The responsiveness of these 42 neurons to baroreceptor and chemoreceptor stimulation by an i.v. injection of three drugs was investigated. For baroreceptor stimulation, methoxamine hydrochloride (Mex) and sodium nitroprusside (SNP) were used; for chemoreceptor stimulation, sodium cyanide (NaCN) was used. Of the 42 neurons, 31 (73.8%) showed an excitatory or inhibitory response to baroreceptor and chemoreceptor stimulation with at least one of the three drugs, and the remaining 11 (26.2%) showed no response. Of these 31 baroreceptor and chemoreceptor-sensitive neurons, 19 (61.3%) responded to two or all three drugs, and the rest (12; 38.7%) responded to one. Most neurons recorded were distributed in the posterior insular cortex. These results indicate that the neurons in the posterior insular cortex receive convergent inputs from the oropharyngolaryngeal region, the baroreceptors and the chemoreceptors, suggesting that the posterior insular cortex may integrate various sensory information.

Regeneração de fibras nervosas periféricas após degeneração induzida por Haloxon

Eventos de neurotoxicidade tardia têm sido freqüentemente associados com intoxicação crônica por organofosforados. Com a finalidade de estudar essa condição em ovelhas, 11 animais receberam uma ou duas doses de 353 ou 500 mg/kg de Haloxon via oral. Os animais intoxicados foram observados diariamente e, entre 16 e 25 dias após a intoxicação, sinais neurológicos de incoordenação e ataxia foram detectados em seis deles. Foram realizadas biópsias de nervos tibiais e laríngeos tão logo a neurotoxicidade foi diagnosticada e, após a morte, fragmentos de nervos periféricos selecionados foram colhidos, juntamente com o sistema nervoso central, para estudos de microscopia óptica, eletrônica de transmissão e de fibras desfiadas. Os nervos tibiais, laríngeos e ciáticos mostraram as alterações mais pronunciadas, que consistiram em degeneração walleriana, ora de uma única fibra, ora de todo um fascículo. Após a morte, exames histológicos revelaram fibras em regeneração com brotamentos axonais crescendo dentro de membranas de células de Schwann, alguns exibindo bainhas finas de mielina.

Nitrergic Innervation of the Rat Larynx Measured by Nitric Oxide Synthase Immunohistochemistry and Nadph-Diaphorase Histochemistry

We evaluated the involvement of nitric oxide (NO) in the laryngeal innervation of rats using NADPH-diaphorase (NADPH-d) histochemistry and neuronal nitric oxide synthase (nNOS) immunohistochemistry. The findings obtained by NADPH-d histochemistry were identical with those obtained by nNOS immunohistochemistry, indicating that NADPH-d is nNOS in the laryngeal innervation system. We found NADPH-d-positive nerve fibers in every region of the larynx. In the epithelia of the mucosa, a small number of NADPH-d-positive nerve fibers were detected. The plexus of NADPH-d-positive nerve fibers was commonly found in the lamina propria, and some of these fibers were clearly associated with blood vessels. We also noted NADPH-d-positive nerve fibers in the region of laryngeal glands. Some of these fibers appeared to terminate in the glandular cells. We found NADPH-d-positive nerve fibers with varicosities in the intrinsic laryngeal muscle and free-ending nerve fibers on the muscle fiber. Motor end plate-like structures were positive for NADPH-d histochemistry. The NADPH-d-positive nerve fibers appeared to terminate at motor end plate-like structures in two of nine rats examined. A cluster of NADPH-d-positive neurons were occasionally present in the lamina propria of the laryngeal mucosa, in the connective tissue between the thyroid cartilage and intrinsic laryngeal muscle, and in the connective tissue near the cricoarytenoid joint. The present findings suggest that NO participates in the autonomic, sensory, and motor innervation of the larynx.

Intraoperative identification of laryngeal nerves with laryngeal electromyography.

The laryngeal nerves are at risk during thyroid surgery, and several techniques have been described for their intraoperative identification to minimize potential damage. Nerve protection is based on the electromyographic recording from the muscles innervated by the laryngeal nerves, and that electrical activity is picked up by various techniques. We evaluated an electrode attachment to the endotracheal tube that provides a stable method for continuous recording of the laryngeal electromyogram. In addition, we tested various modalities of electrical stimulation in the region where the nerves are located, identified the most reliable evoked electromyographic activity, and characterized the wave form and latency. The results, obtained in 28 patients scheduled for thyroid and parathyroid surgery, indicate that the technique of recording from electrodes attached to the endotracheal tube is safe and reliable. Insulated bipolar forceps or a monopolar electrode was used to deliver low-voltage pulses (1 to 3 V) at 1 to 2 pulses/s generated by either battery-operated or optically isolated stimulators. The most unequivocal recordings were obtained with the monitoring equipment set to the nerve-conduction velocity modality, with the sweep set at 2 msec/cm. The technique clearly differentiated the evoked electromyographic responses obtained from the superior or recurrent laryngeal nerve and was easily performed with no perioperative complications.

Osteosynthesis of the cervical spine with an anterior plate.

Osteosynthesis with an anterior plate is indicated for stabilization of the cervical spine. It is used for reconstruction of the vertebral body following corpectomy and for cervical instability due to fractures, fracture-dislocations, and post-laminectomy. In these situations, a well-keyed anterior graft or posterior fusion alone may be inadequate to attain stability. The authors retrospectively review 25 cases of osteosynthesis of the cervical spine using the AO H-plate. All the patients were stable enough postoperatively to allow early mobilization with a cervicothoracic orthosis. Average follow up was 31.2 months. All the grafts fused; however, complications occurred in 36% of the cases. The majority of these complications did not affect the long-term clinical result. This method involves potential risks to the spinal cord, esophagus, carotid structures, and laryngeal nerve. It should therefore be used in carefully selected cases.

Analysis of recurrent laryngeal inspiratory discharges in relation to fast rhythms.

1. Inspiratory (I) activities of recurrent laryngeal (RL) motoneurons and efferent nerves were studied by autospectral, interval, and coherence analyses, with emphasis on fast rhythms of two types: medium-frequency oscillations (MFO, usual range 20-50 Hz for nerve autospectral peaks) and high-frequency oscillations (HFO, usual range 50-100 Hz). 2. In decerebrate, paralyzed, and artificially ventilated cats, recordings were taken from 27 isolated single RL fibers (14 cats) and 8 identified RL motoneurons in the medulla (6 cats), together with recordings of phrenic (PHR) and RL whole-nerve activities. In another 50 cats, RL and PHR nerve discharges were recorded simultaneously. 3. The autospectra of RL units showed prominent MFO peaks with frequencies close to that of the RL nerve MFO spectral peak, indicating presence of this type of fast rhythm in the units' discharges. Spectral analysis of RL unit activity in different segments of the I phase showed that the frequency of a unit's MFO was very close to the peak (maintained) firing rate of the unit during the portion of I analyzed. Thus a motoneuron's MFO spectral peak reflected its rhythmic discharge arising from the cell's refractoriness (and possibly with the rate changing in the course of I). 4. The coherences of motoneurons' MFOs to nerve MFOs were very low or 0, indicating that correlations between unitary MFOs of the RL population were rare and/or weak. 5. In those cats (19/20) that had discernible PHR nerve HFO autospectral peaks, about half of the recorded RL motoneurons (16/34) had HFO. For these motoneurons, the unit-nerve HFO coherences were substantial, indicating widespread correlations between unitary HFOs. 6. In a fraction of cats, coherence peaks in the MFO frequency range were observed between bilateral RL nerves, and between RL and PHR nerves, at frequencies that were subharmonics of the HFO frequency. 7. In light of theoretical considerations on the generation of aggregate rhythms from superposition of unitary rhythms, these observations indicate that, similarly, to the case of PHR motoneurons and nerves. 1) RL nerve MFO arises from superposition of uncorrelated, or at most partially correlated, MFOs of RL units, representing the rhythmic discharges of the cells. It is manifested therefore as a spectral deflection with a maximum in the band of peak firing rates of the units. 2) RL nerve HFO arises from correlated, common-frequency HFOs in a subpopulation of RL units, caused by HFO inputs from antecedent medullary I neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Differential neuromuscular effects of vecuronium on the adductor and abductor laryngeal muscles and tibialis anterior muscle in dogs

We have studied in dogs the neuromuscular blocking effects of vecuronium on the cricothyroid (CT) (a tensor muscle of the vocal folds) and posterior cricoarytenoid (PCA) (sole abductor muscle of the vocal folds) muscles of the larynx and the tibialis anterior (TA) muscle. The lungs of the animals were ventilated mechanically with 0.2% halothane and oxygen. Electromyography (EMG) was performed on the CT, PCA and TA muscles by inserting fine wire electrodes. The evoked compound EMG responses of the three muscles were measured simultaneously in an identical manner by stimulating supramaximally the superior laryngeal, recurrent and sciatic nerves at 0.1 Hz and 0.2 ms. Vecuronium was infused continuously at a rate of 0.01 mg kg-1 min-1 for 8 min. Vecuronium produced more intense neuromuscular block in the CT than in the PCA and TA muscles. The rate of recovery was significantly slowly in the CT compared with the PCA and TA muscles. This study confirms the difference in sensitivity between laryngeal and peripheral muscles, demonstrating that the intrinsic laryngeal muscles do not all behave similarly after administration of vecuronium.

CGRP-immunoreactive cells supplying laryngeal sensory nerve fibres in the cat's nodose ganglion

Through a combination of retrograde staining by wheat germ agglutinin (WGA) and immunohistochemistry, calcitonin gene-related peptide (CGRP)-reactive sensory neurons projecting from the laryngeal mucosa were detected in the feline nodose ganglion. The size of the CGRP-immunoreactive cell which was regarded as a laryngeal sensory neuron, was about 60 microns in diameter: the shape of the immunoreactive laryngeal sensory neuron was unipolar. CGRP-reacted laryngeal sensory cells were found in the rostral part of the nodose ganglion extending to the middle part. They aggregated in the most rostral part, were sparse in other parts and were approximately 50 per cent of WGA-reactive laryngeal sensory neurons in number. Our results suggest that this neurotransmitter might play an important role in laryngeal peripheral sensory innervation.