Laryngeal electromyography with separated surface electrodes in patients with multiple system atrophy presenting with vocal cord paralysis

Vocal Fold Motion Impairment in Neurodegenerative Diseases

Vocal fold motion impairment (VFMI) is the inappropriate movement of the vocal folds during respiration, leading to vocal fold adduction and/or abduction problems and causing respiratory and vocal impairments. Neurodegenerative diseases (NDDs) are a wide range of disorders characterized by progressive loss of neurons and deposition of altered proteins in the brain and peripheral organs. VFMI may be unrecognized in patients with NDDs. VFMI in NDDs is caused by the following: laryngeal muscle weakness due to muscular atrophy, caused by brainstem and motor neuron degeneration in amyotrophic lateral sclerosis; hyperactivity of laryngeal adductors in Parkinson's disease; and varying degrees of laryngeal adductor hypertonia and abductor paralysis in multiple system atrophy. Management of VFMI depends on whether there is a presence of glottic insufficiency or insufficient glottic opening with/without severe dysphagia. VFMI treatment options for glottic insufficiency range from surgical interventions, including injection laryngoplasty and medialization thyroplasty, to behavioral therapies; for insufficient glottic opening, various options are available based on the severity and underlying cause of the condition, including continuous positive airway pressure therapy, botulinum toxin injection, tracheostomy, vocal fold surgery, or a combination of interventions. In this review, we outline the mechanisms, clinical features, and management of VFMI in NDDs and provide a guide for physicians who may encounter these clinical features in their patients. NDDs are always progressive; hence, timely evaluation, proper diagnosis, and appropriate management of the patient will greatly affect their vocal, respiratory, and swallowing functions as well as their quality of life.

Histopathological Features of Gerhardt Syndrome in a Patient With Multiple System Atrophy: An Autopsy Case Report

Multiple system atrophy (MSA) is a progressive neurodegenerative disease characterized by autonomic failure, parkinsonism, and cerebellar ataxia. Gerhardt syndrome, which is inspiratory dyspnea with laryngeal stridor associated with dysfunction of the vocal folds, is a frequent and fatal complication of MSA. A 59-year-old man with a six-year history of MSA presented with ataxia and dysarthria. He also had dyspnea and stridor, which had worsened in the last three months, and died from respiratory distress. Autopsy revealed neurogenic group atrophy of the posterior cricoarytenoid (PCA) muscle, which suggested that laryngeal nerve damage caused abductor vocal fold paralysis in addition to cerebellar and brainstem atrophy with glial cytoplasmic inclusions. Our histopathological findings suggest that Gerhardt syndrome may be associated with neurogenic atrophy of the laryngeal abductor muscle (PCA muscle) of the vocal folds.

Stridor during sleep: description of 81 consecutive cases diagnosed in a tertiary sleep disorders center

Study Objectives

To describe the characteristics of stridor during sleep (SDS) in a series of adults identified by video-polysomnography (V-PSG).

Methods

Retrospective clinical, V-PSG, laryngoscopic, and therapeutic data of patients diagnosed with SDS in a tertiary referral sleep disorders center between 1997 and 2017.

Results

A total of 81 patients were identified (56.8% males, age 61.8 ± 11.2 years). Related etiologies were multiple system atrophy (MSA), amyotrophic lateral sclerosis, spinocerebellar ataxia type 1, anti-IgLON5 disease, fatal familial insomnia, brainstem structural lesions, vagus nerve stimulation, recurrent laryngeal nerve injury, the effect of radiotherapy on the vocal cords, cervical osteophytes, and others. Stridor during wakefulness coexisted in 13 (16%) patients and in MSA was only seen in the parkinsonian form. Laryngoscopy during wakefulness in 72 (88.9%) subjects documented vocal cord abductor impairment in 65 (90.3%) and extrinsic lesions narrowing the glottis in 2 (2.4%). The mean apnea–hypopnea index (AHI) was 21.4 ± 18.6 and CT90 was 11.5 ± 19.1. Obstructive AHI > 10 occurred in 52 (64.2%) patients and central apnea index >10 in 2 (2.4%). CPAP abolished SDS, obstructive apneic events and oxyhemoglobin desaturations in 58 of 60 (96.7%) titrated patients with optimal pressure of 9.0 ± 2.3 cm H20. Tracheostomy in 19 (23.4%) and cordotomy in 3 (3.7%) subjects also eliminated SDS.

Conclusions

SDS in adults is linked to conditions that damage the brainstem, recurrent laryngeal nerve, and vocal cords. V-PSG frequently detects obstructive sleep apnea and laryngoscopy usually shows vocal cord abductor dysfunction. CPAP, tracheostomy, and laryngeal surgery abolish SDS.

Laryngeal Movement Disorders in Multiple System Atrophy: A Diagnostic Biomarker?

Background

Multiple system atrophy (MSA) is a rare neurodegenerative disorder, and its parkinsonian variant can be difficult to delineate from Parkinson's disease (PD). Despite laryngeal dysfunction being associated with decreased life expectancy and quality of life, systematic assessments of laryngeal dysfunction in large cohorts are missing.

Objectives

The objective of this study was to systematically assess laryngeal dysfunction in MSA and PD and identify laryngeal symptoms that allow for differentiating MSA from PD.

Methods

Patients with probable or possible MSA underwent flexible endoscopic evaluation of swallowing performing a systematic task protocol. Findings were compared with an age‐matched PD cohort.

Results

A total of 57 patients with MSA (64 [59–71] years; 35 women) were included, and task assessments during endoscopic examination compared with 57 patients with PD (67 [60–73]; 28 women). Patients with MSA had a shorter disease duration (4 [3–5] years vs 7 [5–10]; P < 0.0001) and higher disease severity (Hoehn & Yahr stage 4 [3–4] vs 3 [2–4]; P < 0.0001). Of the patients with MSA, 43.9% showed clinically overt laryngeal dysfunction with inspiratory stridor. During endoscopic task assessment, however, 93% of patients with MSA demonstrated laryngeal dysfunction in contrast with only 1.8% of patients with PD (P < 0.0001). Irregular arytenoid cartilages movements were present in 91.2% of patients with MSA, but in no patients with PD (P < 0.0001). Further findings included vocal fold motion impairment (75.4%), paradoxical vocal fold motion (33.3%), and vocal fold fixation (19.3%). One patient with PD showed vocal fold motion impairment.

Conclusion

Laryngeal movement disorders are highly prevalent in patients with MSA when assessed by a specific task protocol despite the lack of overt clinical symptoms. Our data suggest that irregular arytenoid cartilage movements could be used as a clinical marker to delineate MSA from PD with a specificity of 1.0 and sensitivity 0.9. © 2020 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Treatment of movement disorder emergencies

Movement disorder emergencies are defined as clinical scenarios where a movement disorder develops over hours to days, and in which morbidity and even mortality can result from failure to appropriately diagnose and manage the patient. The last decade has seen increasing recognition of various movement disorder emergencies, including acute parkinsonism, neuroleptic malignant syndrome, respiratory compromise in multiple system atrophy, dystonic storm, oculogyric crisis, and hemiballism, among others. This article will review the major movement disorder emergencies encountered in the hospital and office, emphasizing practical management and treatment.

[Experimental vocal cord abduction impairment with an artificial vocal cord]

Non-invasive positive pressure ventilation (NPPV) has recently been applied to the patients with multiple system atrophy (MSA) with various respiratory complications including vocal cord abduction impairment and respiratory disturbance by the central origin. Any consensus guidelines on setting up the inspiratory positive airway pressure (IPAP) and expiratory one (EPAP), however, have not been raised yet. To investigate this problem, we made the upper airway tract model with moderately and severely narrow glottis using a training/test lung and the artificial vocal cord which was developed for a humanoid talking robot in Waseda University. The artificial vocal cord was molded out of a high performance thermoplastic rubber in imitation of the human larynx. Previous studies using with a high-speed camera and a sound analyzer showed that the artificial vocal cord resembled human larynx closely both morphologically and functionally. The opening and closing movements of the artificial vocal cord were observed fiberscopically under various conditions of IPAP (4-20 cmH2O) and EPAP (4-10 cmH2O). The maximal glottic width during inspiration and expiration were measured by a pair of calipers on the video-monitored display. Both of the moderately and the severely narrow artificial vocal cords without non-paralytic factors showed typical paradoxical movement showing adduction in inspiration and abduction in expiration, which is characteristic to vocal cord abductor impairment seen in MSA. In the model with moderately severe narrow glottis, this paradoxical movement was released under any positive pressures of continuous (CPAP) and bilevel (Bilevel PAP) modes. In the model with severely narrow glottis, however, there existed a threshold in setting up the optimal EPAP to release the paradoxical movement. In conclusion, EPAP-leading procedure seems to be preferable to IPAP-leading procedure to dilate the narrow glottis as a pneumatic splint in the managements of the patients with MSA presenting with a paralytic type of vocal cord abductor impairment.

Neuromuscular junctions of the posterior cricoarytenoid muscle in multiple system atrophy: a case study

CONCLUSION

The present study showed a variety of stages of neurogenic degeneration of the muscle fibers and the neuromuscular junctions (NMJs) of the posterior cricoarytenoid (PCA) muscle in multiple system atrophy (MSA). These findings coincide with abductor paralysis of vocal cords. Ultrastructural features of the NMJs of the PCA muscle in MSA were different from those of previous studies on experimental resection of recurrent nerve and amyotrophic lateral sclerosis (ALS).

OBJECTIVES

MSA may influence various respiratory functions. Upper airway tracts including larynx are affected without exception during its clinical course. Morphological changes of NMJs of the intrinsic laryngeal muscle in MSA were examined ultrastructurally.

PATIENT AND METHODS

The patient was a 68-year-old male complaining of recurrent aspiration pneumonia, dysphagia, respiratory disturbance, and abductor paralysis of vocal cords. The motor nerve terminals of the PCA muscle in a patient with MSA were investigated electron microscopically.

RESULTS

The NMJs showed varying degrees of ultrastructural changes by motor nerve degeneration. They were seen in the pre- and post-synaptic regions. Muscle fibers losing nerve terminals showed severe damage in their cytoplasm.

Vocal fold paresis and paralysis: what the thyroid surgeon should know

The thyroid surgeon must have a thorough understanding of laryngeal neuroanatomy and be able to recognize symptoms of vocal fold paresis and paralysis. Neuropraxia may occur even with excellent surgical technique. Patients should be counseled appropriately, particularly if they are professional voice users. Preoperative or early postoperative changes in voice, swallowing, and airway function should prompt immediate referral to an otolaryngologist. Early recognition and treatment may avoid the development of complications and improve patient quality of life.

Vocal cord abductor paralysis in multiple system atrophy: a case report

Multiple system atrophy (MSA) is a progressive neurodegenerative disease that is characterized by varying degrees of parkinsonism and cerebellar, corticospinal, and autonomic dysfunction. Vocal cord abductor paralysis (VCAP) is considered a sign of a poor prognosis in MSA, because it is a life-threatening complication that may cause nocturnal sudden death. This case report presents a patient who was treated for Parkinson's disease, and complained of dizziness and sleep apnea. We examined VCAP using fiberoptic laryngoscopy as the possible cause of sleep apnea. VCAP usually occurs in the advanced stages of MSA and is accompanied by a worsening of other symptoms. Optokinetic nystagmus was severely impaired and the caloric test response was bilaterally absent. Objective findings such as VCAP and abnormal neuro-otological results led to the diagnosis of MSA.

Paradoxical vocal cord motion: A review focused on multiple system atrophy

OBJECTIVE

Paradoxical vocal cord motion (PVCM) is a well recognized respiratory condition in which active adduction of the vocal cords during inspiration causes functional airway obstruction. It is considered that laryngeal reflex acceleration underlies the generation of nonorganic PVCM. In various situations producing PVCM, multiple system atrophy (MSA) is a representative neurological disease causing nocturnal laryngeal stridor attributed to PVCM. The purpose of this review is to identify the underlying mechanisms associated with nonorganic and MSA-related PVCM. The following issues are addressed in this review: (1) the pathophysiology of nonorganic and MSA-related PVCM, (2) the relationships between PVCM and airway reflexes, and (3) the treatment for MSA-related PVCM.

METHODS

Review.

RESULTS AND CONCLUSIONS

An abnormality of the laryngeal output-feedback control underlies nonorganic PVCM, which is usually triggered by an excessive response to external and internal airway stimuli. Similarly, several clinical and experimental evidence suggest that MSA-related PVCM is attributed to the airway reflex as well as to paradoxical central outputs resulting from the MSA-induced damage to the pontomedullary respiratory center. Application of continuous positive airway pressure (CPAP), which suppresses the reflexive inspiratory activation of adductors, is recommended as the treatment for MSA-related PVCM.

Vocal fold paresis and paralysis

Diagnosis and treatment of the immobile or hypomobile vocal fold are challenging for the otolaryngologist. True paralysis and paresis result from vocal fold denervation secondary to injury to the laryngeal or vagus nerve. Vocal fold paresis or paralysis may be unilateral or bilateral, central or peripheral, and it may involve the recurrent laryngeal nerve, superior laryngeal nerve, or both. The physician's first responsibility in any case of vocal fold paresis or paralysis is to confirm the diagnosis and be certain that the laryngeal motion impairment is not caused by arytenoid cartilage dislocation or subluxation, cricoarytenoid arthritis or ankylosis, neoplasm, or other mechanical causes. Strobovideolaryngoscopy, endoscopy, radiologic and laboratory studies, and electromyography are all useful diagnostic tools.

Laryngeal response to nasal ventilation in nonsedated newborn lambs

Although endoscopic studies in adult humans have suggested that laryngeal closure can limit alveolar ventilation during nasal intermittent positive pressure ventilation (nIPPV), there are no available data regarding glottal muscle activity during nIPPV. In addition, laryngeal behavior during nIPPV has not been investigated in neonates. The aim of the present study was to assess laryngeal muscle response to nIPPV in nonsedated newborn lambs. Nine newborn lambs were instrumented for recording states of alertness, electrical activity [electromyograph (EMG)] of glottal constrictor (thyroarytenoid, TA) and dilator (cricothyroid, CT) muscles, EMG of the diaphragm (Dia), and mask and tracheal pressures. nIPPV in pressure support (PS) and volume control (VC) modes was delivered to the lambs via a nasal mask. Results show that increasing nIPPV during wakefulness and quiet sleep led to a progressive disappearance of Dia and CT EMG and to the appearance and subsequent increase in TA EMG during inspiration, together with an increase in trans-upper airway pressure (TUAP). On rare occasions, transmission of nIPPV through the glottis was prevented by complete, active glottal closure, a phenomenon more frequent during active sleep epochs, when irregular bursts of TA EMG were observed. In conclusion, results of the present study suggest that active glottal closure develops with nIPPV in nonsedated lambs, especially in the VC mode. Our observations further suggest that such closure can limit lung ventilation when raising nIPPV in neonates.

[When should tracheotomy be performed in bilateral vocal cord paralysis involving multiple system atrophy?]

OBJECTIVES

Bilateral vocal cord paralysis caused by central nervous system dysfunction results from such diverse causes as cerebrovascular disorder and neurodegenerative disease. Otolaryngologists are often consulted about indications of tracheostomy for such cases, but if their recognition of causative disease is insufficient, it is difficult to judge indications of tracheostomy. We reviewed tracheostomy cases due to bilateral vocal cord paralysis caused by multiple system atrophy (MSA) and considered points to keep in mind in such cases.

MATERIALS AND METHODS

We diagnosed 9 cases of vocal cord midline fixation due to central bilateral vocal cord paralysis caused by MSA and treated by tracheostomy. We reviewed clinical conditions and suitable time for tracheostomy because it presents a specific clinical course.

RESULTS

7 cases were MSA-P and 2 cases were MSA-C. Inspiratory stridor in awaking and dysphasia was aggravated at the almost same time in 7 cases.

DISCUSSION

Vocal cord abductor paralysis in MSA may cause sudden death, but when an otolaryngologist not familiar with this disease is asked for air way evaluation, it is possible to be diagnosed as no vocal cord paralysis because there is no an adductor disorder, so clinical course of MSA should be clarified more. In vocal cord midline fixation, it was expected that intervention by hypermyotony in the progress of Parkinsonism was a main factor, as was vocal cord abductor disorder due to a neurogenic change in the posterior cricoarytenoid muscle in MSA. The aggravation of dysphasia is an important index in judging the indication of tracheostomy.

Non-invasive positive pressure ventilation for laryngeal contraction disorder during sleep in multiple system atrophy

We examined the usefulness of non-invasive positive pressure ventilation (NPPV) in the management of nocturnal laryngeal stridor associated with vocal cord dysfunction in five cases of multiple system atrophy (MSA). First, the patients were investigated during sleep induced by a minimal dose of propofol. Laryngoscopy showed paradoxical vocal cord movement resulting in inspiratory stridor. Electromyographic (EMG) study revealed synchronized bursts in the thyroarytenoid muscles and diaphragm in every inspiratory phase whenever the stridor emerged. NPPV was initiated after paradoxical movement was recognized with laryngoscopy. The NPPV mask was equipped with an additional channel for laryngoscopic monitoring. The optimal pressure for treatment was determined according to laryngoscopic and EMG findings. Next, NPPV was applied to natural sleep using the conditions determined in propofol-induced sleep. In all cases, NPPV eliminated nocturnal stridor and oxygen desaturation during natural sleep. Laryngoscopic observation during induced sleep is recommended as a useful procedure to titrate the optimal pressure for NPPV therapy. Since central hypoventilation progresses in the course of MSA, the choice of NPPV rather than continuous positive airway pressure should be encouraged to treat laryngeal contraction disorder associated with MSA.

Repetitive phonatory tasks for identifying vocal fold paresis

Vocal fold paresis may be present in patients with voice complaints. Identification of paresis is important so that appropriate neurolaryngologic evaluation can be ordered and the appropriate treatment can be offered. Repetitive phonatory tasks (RPTs) fatigue patients vocally and may elicit signs of subtle paresis. In this study, four laryngologists independently reviewed the RPT portions of routine fiberoptic voice examinations of 100 patients in a blinded fashion. All patients had presented with voice complaints, were suspected of having a movement disorder of the larynx, and had been referred for laryngeal electromyography (LEMG). Predictions were compared with LEMG results and with predictions made at the time of each initial evaluation. Although RPTs are useful to laryngologists, predictions based on the entire examination are more accurate. LEMG can confirm clinical suspicions or identify paresis missed on fiberoptic laryngeal examination.

Tracheostomy abolishes paradoxical activation of the vocal cord adductor in multiple system atrophy

OBJECTIVES

Inspiratory activation of the vocal cord adductor, which causes paradoxical vocal cord motion, develops in patients with multiple system atrophy (MSA). To confirm the hypothesis that airway reflexes trigger such paradoxical activation, we investigated the effects of tracheostomy on the adductor activation in a MSA patient.

METHODS

We compared the adductor electromyograms before and after breathing was diverted to a tracheostoma under propofol anesthesia.

RESULTS

The adductor inspiratory activation disappeared during tracheostoma breathing.

CONCLUSION

Airway reflexes as well as MSA-related damage to the respiratory center contribute to the generation of paradoxical adductor activation in MSA patients.

Inspiratory activation of the vocal cord adductor, part II: Animal study in the cat

OBJECTIVES/HYPOTHESIS

The authors have shown previously that the vocal cord adductor is activated during inspiration in patients with vocal cord abduction impairment and that this adductor inspiratory activity is abolished by relief from inspiratory tracheal negative pressure by opening the tracheostoma. (Shiba K. Isono S, Sekita Y, Tanaka A. Inspiratory activation of the vocal cord adductor, Part I: human study in patients with restricted abduction of the vocal cords. Laryngoscope 2004;114:372-375). The authors hypothesized that insufficient opening of the glottis during inspiration generates strong negative pressure in the trachea and that this negative pressure triggers an airway reflex that activates the adductor.

STUDY DESIGN

Experimental study of the mechanism of laryngeal obstruction using an animal model of restricted abduction of the vocal cords.

METHODS

To identify such an airway reflex, the authors recorded the adductor electromyogram in anesthetized cats whose vocal cords were mechanically adducted by stitching both cords together. To determine whether this reflex modulation of adductor activity is induced through afferents from the larynx or from the lower airway, the authors applied negative pressure to the subglottic space and lower airway separately.

RESULTS

The adductor was activated during inspiration with powerful negative pressure in the trachea. Negative pressure in the subglottic space had a more marked effect on the adductor activity than did pressure in the lower airway. The adductor inspiratory activity was virtually abolished by laryngeal deafferentation.

CONCLUSION

Glottal narrowing during inspiration reflexly activates the vocal cord adductor. This paradoxical inspiratory-related adductor activation is induced by an airway reflex triggered mainly through afferents from the larynx and probably contributes to stridor and dyspnea in patients with laryngeal obstruction.

Inspiratory Activation of the Vocal Cord Adductor, Part I: Human Study in Patients With Restricted Abduction of the Vocal Cords

OBJECTIVES/HYPOTHESIS

In patients with restricted abduction of the vocal cords, it has generally been accepted that glottis narrowing with laryngeal stridor during inspiration is attributed to static and passive obstruction of the glottis. However, active glottis narrowing can also be contributory. We tested the hypothesis that the vocal cord adductor is activated during inspiration in patients with restricted abduction of the vocal cords.

STUDY DESIGN

Electromyographic evaluation of vocal cord adductor activity in patients with restricted abduction of the vocal cords.

METHODS

Five patients with restricted abduction of the vocal cords who had stridor with mild to severe dyspnea during wakefulness were anesthetized with propofol. We recorded the adductor muscle electromyogram during breathing through a laryngeal mask airway while observing the vocal cord movement endoscopically. In three patients who had undergone tracheostomy, we also recorded adductor firing patterns not only while closing but also while opening the tracheostoma.

RESULTS

The adductor was activated during inspiration, and the glottis was narrowed in accordance with inspiratory stridor. This adductor inspiratory activity was abolished by opening the tracheostoma in the tracheostomized patients.

CONCLUSION

Not only static or passive glottis narrowing but also active narrowing may contribute to inspiratory flow limitation in patients with restricted abduction of the vocal cords. This active glottis narrowing is probably induced by an airway reflex.

Different mechanism of vocal cord paralysis between spinocerebellar ataxia (SCA 1 and SCA 3) and multiple system atrophy

While multiple system atrophy (MSA) is frequently associated with vocal cord paralysis (VCP) causing severe respiratory failure, it is still unknown whether hereditary types of spinocerebellar degeneration develop similar laryngeal paralysis. We analyzed the laryngeal function from the viewpoints of fiberoptic laryngoscopy and laryngeal myopathology and then attempted to clarify the difference of the mechanism of VCP among the patients with spinocerebellar ataxia type 1 (SCA 1), type 3 (SCA 3), and MSA. Seven patients with SCA 1, nineteen with SCA 3, and eleven with MSA were studied. Vocal cord movement was analyzed by fiberoptic laryngoscopy during wakefulness and diazepam-induced sleep (sleep load test). Paraffin-embedded sections or cryosections of the intrinsic laryngeal muscles from five autopsied cases (one with SCA 1 and four with SCA 3) were histologically examined. VCP was found in two of the seven SCA 1 patients (29%), three of the nineteen SCA 3 patients (16%), and in nine of the eleven MSA patients (82%). VCP observed in SCA 1 and SCA 3 was various in the severity and showed no exacerbation on sleep load test in all of the eight patients but one SCA 3 patient. In this patient, the findings of fiberoptic laryngoscopy were quite similar to those found in MSA. All the intrinsic laryngeal muscles including cricothyroid (CT), interarytenoid (IA), and posterior cricoarytenoid (PCA) muscles showed neurogenic atrophy in one autopsied SCA 1 and four SCA 3 patients. Our conclusion is that VCP in SCA 1 and SCA 3 contrasts with that in MSA in its occurrence, response to the sleep load test, and the distribution of the neurogenic abnormalities among the intrinsic laryngeal muscles.

Pathogenesis of laryngeal narrowing in patients with multiple system atrophy

1. We do not fully understand the pathogenesis of nocturnal laryngeal stridor in patients with multiple system atrophy (MSA). Recent studies suggest that inspiratory thyroarytenoid (TA) muscle activation has a role in the development of the stridor. 2. The breathing pattern and firing timing of TA muscle activation were determined in ten MSA patients, anaesthetized with propofol and breathing through the laryngeal mask airway, while the behaviour of the laryngeal aperture was being observed endoscopically. 3. Two distinct breathing patterns, i.e. no inspiratory flow limitation (no-IFL) and IFL, were identified during the measurements. During IFL, significant laryngeal narrowing was observed leading to an increase in laryngeal resistance and end-tidal carbon dioxide concentration. Development of IFL was significantly associated with the presence of phasic inspiratory activation of TA muscle. Application of continuous positive airway pressure suppressed the TA muscle activation. 4. The results indicate that contraction of laryngeal adductors during inspiration narrows the larynx leading to development of inspiratory flow limitation accompanied by stridor in patients with MSA under general anaesthesia.

Stridor and death in multiple system atrophy

Patients with multiple system atrophy (MSA) have a mean survival of 8 to 10 years. Nocturnal stridor has been considered a poor prognostic feature. We analyzed demographic, clinical, and polysomnographic data and obtained follow-up information from 42 patients with MSA (30 with follow-up data) seen in a Sleep Disorders Center. Group I consisted of 17 patients with nocturnal stridor, including seven with daytime stridor. Group II consisted of 25 patients without stridor. Analysis of survival curves of 30 patients with follow-up information showed a significantly shorter survival from the sleep evaluation, but not from disease onset, for patients with stridor compared with those without. Nine of 11 patients with stridor died a median of 2 years from presentation and the only two survivors had undergone tracheostomy. Patients with daytime stridor and immobile vocal cords had especially poor prognoses. However, two of four patients with tracheostomies also died, as did six of 19 without stridor. We postulate that central hypoventilation and its complications may have been responsible for many of these other deaths. We conclude that stridor does carry a poor prognosis in patients with MSA but that there are also other causes of death. We recommend consideration of tracheostomy for patients with MSA who have stridor, but also assessment for central hypoventilation and appropriate management if it is present.

Early diagnosis and stage classification of vocal cord abductor paralysis in patients with multiple system atrophy

OBJECTIVES

Vocal cord abductor paralysis (VCAP) is a life threatening complication which may cause nocturnal sudden death in patients with multiple system atrophy. However, the early diagnosis of VCAP is often difficult to make on routine laryngoscopy performed during wakefulness, as stridor, which is the sole symptom of VCAP in the early stage, develops only during sleep. The aim was to investigate laryngeal dysfunction in patients with multiple system atrophy while awake and asleep.

METHODS

Seven patients with multiple system atrophy with nocturnal stridor and five control patients were studied. Vocal cord movement was analysed by laryngoscopy while the patients were awake and also during sleep induced by intravenous diazepam.

RESULTS

When awake, for the seven patients with multiple system atrophy normal movement of the vocal cords occurred in three, mild abduction restriction in three, and paradoxical movement in one. When asleep, however, all showed obvious paradoxical movement with high pitched inspiratory stridor. In controls, there were no differences in the vocal cord movement between wakefulness and sleep. From these findings, VCAP could be divided into four stages: stage 0 (normal) with normal vocal cord movement during both wakefulness and sleep, stage 1 (mild VCAP) with normal movement during wakefulness and paradoxical movement during sleep, stage 2 (moderately severe VCAP) with abduction restriction during wakefulness and paradoxical movement during sleep, and stage 3 (severe VCAP) with an almost midline position for the vocal cords during both wakefulness and sleep.

CONCLUSIONS

Laryngoscopy during sleep can disclose subclinical VCAP, making an early diagnosis of VCAP in patients with multiple system atrophy. Stage 2 of VCAP seems to be a suitable stage for tracheostomy in patients with multiple system atrophy.

Vocal cord abductor paralysis (VCAP) in Parkinson's disease: difference from VCAP in multiple system atrophy

Vocal cord abductor paralysis (VCAP) is rare in Parkinson's disease (PD), while it is frequent in multiple system atrophy (MSA). Although VCAP is a life-threatening complication it has not yet been clarified whether there is any difference in the mechanism of VCAP between PD and MSA. Examining 3 autopsy-proven PD patients who developed severe VCAP requiring tracheostomy, we found the following differences in the mechanism of VCAP between MSA and PD: (1) clinical and laryngofiberscopic examination showed that VCAP in PD was not exacerbated during sleep, unlike in MSA; (2) On histological examination of the intrinsic laryngeal muscles, the posterior cricoarytenoid muscle demonstrated no abnormalities in PD, while the muscle showed characteristic neurogenic atrophy in MSA. There seemed to be two types of VCAP, namely the nonparalytic type observed in PD, and the paralytic type observed in MSA. Severe dysphagia requiring tube-feeding was common among PD patients who presented with VCAP. Although the relationship between VCAP and dysphagia is unknown, one should be aware of the possibility of fatal VCAP in PD patients with severe dysphagia.