Atrophy of the posterior cricoarytenoid muscle as an indicator of recurrent laryngeal nerve palsy.
BACKGROUND AND PURPOSE: The posterior cricoarytenoid (PCA) muscle is one of the intrinsic muscles of the larynx innervated by the recurrent laryngeal nerve. As such, recurrent laryngeal nerve palsy should not only result in paralysis of the true vocal cord or thyroarytenoid muscle but also in a similar change in the PCA muscle. The ability of CT and MR imaging to depict denervation atrophy in the PCA muscle in patients with recurrent laryngeal nerve palsy was evaluated. METHODS: Two investigators reviewed the CT and/or MR studies of 20 patients with a clinical history of vocal cord paralysis. The appearance of the PCA muscle was given a rating of 0, 1, 2, 3, or 4, with 0 being definitely normal and 4 being definitely abnormal or atrophic. Each study was also reviewed for the presence or absence of other features of vocal cord paralysis: thyroarytenoid muscle atrophy, anteromedial deviation of the arytenoid cartilage, an enlarged piriform sinus and laryngeal ventricle, and a paramedian cord. RESULTS: Atrophy of the PCA muscle was shown unequivocally in 65% of the cases and was most likely present in an additional 20%. The frequency with which other features of vocal cord paralysis were seen was as follows: thyroarytenoid atrophy, 95%; anteromedial deviation of the arytenoid cartilage, 70%; enlarged piriform sinus, 100%; enlarged laryngeal ventricle, 90%; and a paramedian cord, 100%. CONCLUSION: Atrophy of the PCA muscle may be commonly documented on CT and MR studies in patients with recurrent laryngeal nerve palsy and vocal cord paralysis, and therefore should be part of the constellation of imaging features of vocal cord paralysis. This finding is particularly useful when other imaging findings of vocal cord paralysis are absent or equivocal. (+info)
Quantitative analysis of the anatomy of the epineurium of the canine recurrent laryngeal nerve.
The purpose of this investigation was to determine the amount of epineurium surrounding the recurrent laryngeal nerve (RLN) compared with a limb nerve, that to flexor hallicus longus (NFHL). Nerve samples were obtained from 10 adult dogs and studied using scanning electron microscopy and light microscopy to measure the relative proportion of epineurium and the relative proportions of adipose and collagenous tissue comprising the epineurium in both nerves. Significantly greater relative epineurial cross-sectional areas and adipose content were found in the RLN than in the NFHL. Based on observations on noncranial peripheral nerves, the findings indicate that the RLN is better protected against deformational forces associated with compression than stretching forces. The RLN may not be structured well for successful reinnervation after injury. The patterns observed for adipose tissue in RLN epineurial tissue appeared unique compared with those previously reported in peripheral nerves. The primary role associated with adipose tissue is to 'package' the nerve for protection. The RLN is considered to be a vital nerve in the body, as are other cranial nerves. The large proportions of adipose tissue in the epineurium may relate to the importance of protecting this nerve from injury. (+info)
Synchronized fast rhythms in inspiratory and expiratory nerve discharges during fictive vocalization.
In precollicular decerebrate and paralyzed cats, respiratory nerve activities were recorded during fictive vocalization (FV), which consisted of a distinctive pattern of 1) decreased inspiratory (I) and expiratory (E) phase durations, 2) marked increase of phrenic activity and moderate changes of recurrent laryngeal (RL) and superior laryngeal (SL) I activities, and 3) massive recruitment of laryngeal and abdominal (ABD; lumbar) E activities. FV was produced by electrical stimulation (100 Hz) in the midbrain periaqueductal gray (PAG) or its putative descending pathways in the ventrolateral pons (VLP). Spectral and correlation analyses revealed three types of effect on fast rhythms during FV. 1) I activities: the coherent high-frequency oscillations in I (I-HFO, 60-90 Hz) present in phrenic and RL discharges during the control state did not change qualitatively, but there was an increase of power and a moderate increase (4-10 Hz) of frequency. Sometimes a distinct relatively weak stimulus-locked rhythm appeared. 2) RL and SL activities during E: in recruited discharges, a prominent intrinsic rhythm (coherent E-HFOs at 50-70 Hz) appeared; sometimes a distinct relatively strong stimulus-locked rhythm appeared. 3) ABD activities during E: this recruited activity had no intrinsic rhythm but had an evoked oscillation locked to the stimulus frequency. Thus FV is characterized by 1) appearance of prominent coherent intrinsic rhythms in RL and SL E discharges, which presumably arise as a result of excitation and increased interactions in laryngeal networks; 2) modification of intrinsic rhythmic interactions in inspiratory networks; and 3) evoked rhythms in augmenting-E neuron networks without occurrence of intrinsic rhythms. (+info)
Nonrecurrent laryngeal nerve during carotid artery surgery: case report and literature review.
The anomalous position of a nonrecurrent inferior laryngeal nerve predisposes it to injury during surgery in the neck. We present the case of a patient who underwent a carotid endarterectomy in which a rare left nonrecurrent laryngeal nerve was found intraoperatively. This abnormality, which occurs much less often on the left than the right side of the neck, should be familiar to vascular surgeons. Historical, embryologic, and surgical significance of this anomaly is addressed. (+info)
Left vocal cord paralysis associated with long-standing patent ductus arteriosus.
SUMMARY: Left vocal cord paralysis in association with patent ductus arteriosus is unusual. We report a patient with long-standing patent ductus arteriosus (PDA) in whom CT studies obtained before and after paralysis developed showed an interval increase in size of the pulmonary trunk. The pathogenesis of left vocal cord paralysis in association with long-standing PDA is discussed. (+info)
Relationship between the recurrent laryngeal nerve and the inferior thyroid artery: a study in corpses.
The anatomical relationship between the recurrent laryngeal nerve (RLN) and the inferior thyroid artery (ITA) was studied in 76 embalmed corpses, 8 females and 68 males. In both sexes, the RLN lay more frequently between branches of the ITA.; it was found in this position in 47.3% of male corpses and 42.8% of female ones. On the right, RLN was found between branches of the ITA in 49.3% of the cases, anterior to it in 38.04%, and posterior in 11.26%. On the left, the RLN lay between branches of the ITA in 44.45%, posterior to the ITA in 37.05%, and anterior to it in 18.05% of the cases. In 62.68% of the cases, the relationship found on one side did not occur again on the opposite side. There was a significant difference (p<0.05) in the distribution of the 3 types of relationships between the RLN and the ITA, on the right and on the left. Racial variations could contribute to an explanation of the differences observed by authors of different countries in the relationship between the RLN and the ITA. (+info)
Use of the laryngeal mask airway in thyroid and parathyroid surgery as an aid to the identification and preservation of the recurrent laryngeal nerves.
A prospective study was carried out in patients undergoing thyroid and parathyroid surgery using a laryngeal mask airway (LMA) and electrical nerve stimulation to identify the recurrent laryngeal nerves. A total of 150 consecutive patients undergoing thyroid and parathyroid surgery by a single surgeon were assessed for suitability of anaesthesia via the LMA. Peroperatively, a fibre-optic laryngoscope was passed through the LMA to enable the anaesthetist to visualise the vocal cords while adduction of the cords was elicited by applying a nerve stimulator in the operative field. In all, 144 patients were selected for anaesthesia via the LMA. Fibre-optic laryngoscopy and nerve stimulation were performed in 64 patients (42.7%). The trachea was deviated in 51 (34.0%) and narrowed in 33 (22.0%). The recurrent laryngeal nerves were identified in all patients. There were no cases of vocal cord dysfunction resulting from surgery. The LMA can be safely used for thyroid and parathyroid surgery even in the presence of a deviated or narrowed trachea. It can assist in identification and preservation of the recurrent laryngeal nerve and is, therefore, of benefit to both patient and surgeon. (+info)
Selective suppression of late laryngeal adductor responses by N-methyl-D-aspartate receptor blockade in the cat.
Laryngeal adductor responses to afferent stimulation play a key role in airway protection. Although vital for protection during cough and swallow, these responses also must be centrally controlled to prevent airway obstruction by laryngospasm during prolonged stimulation. Our purpose was to determine the role of N-methyl-D-aspartate (NMDA) receptors in modulating early R1 responses (at 9 ms) and/or later more prolonged R2 responses (at 36 ms) during electrical stimulation of the laryngeal afferent fibers contained in the internal branch of the superior laryngeal nerve in the cat. The percent occurrence, amplitude, and conditioning of muscle responses to single superior laryngeal nerve (SLN) stimuli presented in pairs at interstimulus intervals of 250 ms were measured in three experiments: 1) animals that had ketamine as anesthetic premedication were compared with those who did not, when both were maintained under alpha-chloralose anesthesia. 2) The effects of administering ketamine in one group of animals were compared with increasing the depth of alpha-chloralose anesthesia without NMDA receptor blockade in another group of animals. 3) The effects of dextromethorphan (without anesthetic effects) were examined in another group of animals. In the first experiment, the occurrence of R2 responses were reduced from 95% in animals without ketamine premedication to 25% in animals with ketamine premedication (P = 0.015). No differences occurred in the occurrence, amplitude, latency, or conditioning effects on R1 responses between these groups. In the second experiment, the occurrence of R2 responses was reduced from 96 to 79% after an increase in the depth of anesthesia with alpha-chloralose in contrast with reductions in R2 occurrence from 98 to 19% following the administration of ketamine to induce NMDA receptor blockade along with increased anesthesia (P = 0.025). In the third experiment, R2 occurrence was reduced from 89 to 27% (P = 0.017) with administration of dextromethorphan while R1 response occurrence and amplitude did not change. In each of these experiments, NMDA receptor blockade did not have significant effects on cardiac or respiratory rates in any of the animals. The results demonstrate that NMDA receptors play an essential role in long latency R2 laryngeal responses to laryngeal afferent stimulation. On the other hand, early R1 laryngeal adductor responses are likely to involve non-NMDA receptor activation. (+info)