The Journal of Laryngology and Otology July 1992, Vol. 106, pp. 633-634
Laryngeal stridor in myasthenia gravis ANAND JOB, M.S., R. RAMAN, M.S., C. GNANAMUTHU, M.D., D.M. (Vellore, India)
Abstract Two patients with laryngeal stridor secondary to myasthenia gravis are reported. The cause of bilateral abductor weakness in myasthenia is discussed; anticipation of the stridor in myasthenic patients is highlighted.
pyridostigmine, was admitted under the Neurologists in myasthenic crisis. She also had stridor and hence an ENT consultation was sought. On indirect laryngoscopy, her vocal folds were in the paramedian position. She was administered an injection of edrophonium intravenously to see if the stridor would improve and if the vocal folds would move apart, but no change was observed. This may have been due to the fact that the patient was already on high dose of cholinesterase inhibitors. The patient was advised to undergo a tracheostomy. As the patient requested discharge further management and follow up were not possible.
Introduction Breathlessness and respiratory distress are often a part of the presenting features of advanced myasthenia gravis in crisis, due to weakness of the muscles of respiration. Using the following two case reports as examples, we would like to emphasize that bilateral abductor vocal fold paresis can coexist in such situations. Besides, stridor could be one of the presenting symptoms of myasthenic crisis. This raises three important issues in the management of myasthenic crisis: 1) stridor due to vocal fold paresis may aggravate the already existing respiratory distress. 2) asphyxia and sudden respiratory arrest can occur unless the vocal fold paresis is specifically looked for, and 3) the lines of management would differ if vocal fold paresis is present. Laryngeal stridor as the first manifestation of myasthenia gravis has been reported following anaesthesia (Colp et al., 1980), as well as after exposure to chlorine gas (Foulkes, 1981). There have been rare reports of respiratory failure in myasthenia due to poor vocal fold abductor function (Friedman & Goffin, 1966; Schmidt-Nowara et al., 1984). We report two patients, one who presented to the ENT department in stridor and subsequently found to be in myasthenic crisis and another known to have myasthenia gravis who went into crisis and laryngeal stridor.
Discussion In severe myasthenia gravis involvement of respiratory muscles sometimes necessitating mechanical ventilation is well known. Involvement of the intrinsic muscles of the larynx is however poorly documented and understood. Dysphonia in myasthenia is made worse with prolonged phonation. Poor adduction of the vocal folds results in a breathy voice and weakness in abduction results in stridor and dyspnoea (Neal and Clarke, 1987). It has been clinically observed that in myasthenia gravis, the normally abducted position of the vocal folds is reversed during forced inspiration, with the vocal folds coming together to cause an upper airway obstruction (Schmidt-Nowara et al., 1984). In an experimental study, six volunteers who were given curare to produce a myasthenia-like state experienced increased inspiratory resistance due to upper airway obstruction (Friedman and Goffin, 1966). The frequency of vocal fold paresis and upper airway obstruction in myasthenia is unknown since studies in these patients have not focused on upper airway function (Schmidt-Nowara et al., 1984). Conventional spirometry which measures expiratory function only, will fail to detect the upper airway obstruction and will underestimate the pulmonary impairment, as in such patients expiratory function may be normal. In these patients the inspiratory flow-volume loop should be used to evaluate the respiratory distress (SchmidtNowara et al., 1984). Obstruction of the upper airway may be common in patients with severe respiratory muscle weakness (Schmidt-Nowara et al., 1984). Though this may be detected clinically it may not be considered significant for two reasons, as in our patients (Colp et al., 1980). First, the stridor is of low volume due to respiratory muscle weakness (Foulkes, 1981); secondly, all therapeutic measures are concentrated on improving the respiratory muscle function. Thus the isolated poor vocal fold abductor function is missed and this can lead to respiratory failure (Schmidt-Nowara etal., 1984). Laryngeal stridor is a life-threatening complication of myasthenia gravis. It should be anticipated in every patient who is either in myasthenic crisis or respiratory distress.
Case 1 A 55-year-old woman presented to the ENT department with a sudden onset of stridor and dysphagia of two days duration. On indirect laryngoscopy, both vocal folds were in the paramedian position. No other laryngeal abnormalities were detected. Emergency measures for the stridor were not instituted, as at the time of examination this was only mild and a sufficient gap was seen between the vocal folds to allow adequate ventilation. A physician was called in to see the patient, who detected that she had bilateral ptosis, external opthalmoplegia and moderate weakness of all four limbs and myasthenia was suspected. It was further ascertained that this patient had been experiencing progressive weakness of proximal muscles for two months. While being admitted to the ward for a detailed evaluation, she suddenly had a respiratory arrest. She was immediately resuscitated and a tracheostomy was performed after which she was ventilated as her breathing was inadequate. A positive edrophonium test confirmed the diagnosis of myasthaenia gravis and she was started on treatment. However, she subsequently developed respiratory infection, septicaemia and died. Case 2 A 38-year-old lady, known to have myasthenia gravis and on
Accepted for publication: 18 March 1992 633
634 References Colp, C, Kriplani, L., Nussbaum, N. (1980) Vocal cord paralysis in myasthenia gravis following anaesthesia. Chest, 77: 218-220. Foulkes, C. J. (1981) Myasthenia gravis presenting as laryngeal stridor after exposure to chlorine gas. Southern Medical Journal, 74: 1423-1424. Friedman, S., Goffin, F. B. (1966) Abductor cord vocal weakness in myasthenia gravis. Report of a case. Laryngoscope, 76: 1520-1523. Gal, T. J., Aurora, N. S. (1982) Respiratory mechanics in supine subjects during progressive partial curarization. Journal of Applied Physiology, 52: 57-63. Neal, G. D., Clarke, L. R. (1987) Neuromuscular disorders. Otolaryngologic Clinics of North America, 20 (1): 195-201.
A. JOB, R. RAMAN, C. GNANAMUTHU
Schmidt-Nowara, W. W., Marder, E. J., Feil, P. A. (1984) Respiratory failure in myasthenia gravis due to vocal cord paresis. Archives of Neurology, 41: 567-568. Address for correspondence: R. Raman, Professor and Head, Department of ENT, Christian Medical College and Hospital, Ida Scudder Road, Post Box No. 3, Vellore-632 004, Southern India.
Key words: Respiratory sounds, stridor; Myasthenia gravis
Laryngeal stridor in myasthenia gravis ANAND JOB, M.S., R. RAMAN, M.S., C. GNANAMUTHU, M.D., D.M. (Vellore, India)
Abstract Two patients with laryngeal stridor secondary to myasthenia gravis are reported. The cause of bilateral abductor weakness in myasthenia is discussed; anticipation of the stridor in myasthenic patients is highlighted.
pyridostigmine, was admitted under the Neurologists in myasthenic crisis. She also had stridor and hence an ENT consultation was sought. On indirect laryngoscopy, her vocal folds were in the paramedian position. She was administered an injection of edrophonium intravenously to see if the stridor would improve and if the vocal folds would move apart, but no change was observed. This may have been due to the fact that the patient was already on high dose of cholinesterase inhibitors. The patient was advised to undergo a tracheostomy. As the patient requested discharge further management and follow up were not possible.
Introduction Breathlessness and respiratory distress are often a part of the presenting features of advanced myasthenia gravis in crisis, due to weakness of the muscles of respiration. Using the following two case reports as examples, we would like to emphasize that bilateral abductor vocal fold paresis can coexist in such situations. Besides, stridor could be one of the presenting symptoms of myasthenic crisis. This raises three important issues in the management of myasthenic crisis: 1) stridor due to vocal fold paresis may aggravate the already existing respiratory distress. 2) asphyxia and sudden respiratory arrest can occur unless the vocal fold paresis is specifically looked for, and 3) the lines of management would differ if vocal fold paresis is present. Laryngeal stridor as the first manifestation of myasthenia gravis has been reported following anaesthesia (Colp et al., 1980), as well as after exposure to chlorine gas (Foulkes, 1981). There have been rare reports of respiratory failure in myasthenia due to poor vocal fold abductor function (Friedman & Goffin, 1966; Schmidt-Nowara et al., 1984). We report two patients, one who presented to the ENT department in stridor and subsequently found to be in myasthenic crisis and another known to have myasthenia gravis who went into crisis and laryngeal stridor.
Discussion In severe myasthenia gravis involvement of respiratory muscles sometimes necessitating mechanical ventilation is well known. Involvement of the intrinsic muscles of the larynx is however poorly documented and understood. Dysphonia in myasthenia is made worse with prolonged phonation. Poor adduction of the vocal folds results in a breathy voice and weakness in abduction results in stridor and dyspnoea (Neal and Clarke, 1987). It has been clinically observed that in myasthenia gravis, the normally abducted position of the vocal folds is reversed during forced inspiration, with the vocal folds coming together to cause an upper airway obstruction (Schmidt-Nowara et al., 1984). In an experimental study, six volunteers who were given curare to produce a myasthenia-like state experienced increased inspiratory resistance due to upper airway obstruction (Friedman and Goffin, 1966). The frequency of vocal fold paresis and upper airway obstruction in myasthenia is unknown since studies in these patients have not focused on upper airway function (Schmidt-Nowara et al., 1984). Conventional spirometry which measures expiratory function only, will fail to detect the upper airway obstruction and will underestimate the pulmonary impairment, as in such patients expiratory function may be normal. In these patients the inspiratory flow-volume loop should be used to evaluate the respiratory distress (SchmidtNowara et al., 1984). Obstruction of the upper airway may be common in patients with severe respiratory muscle weakness (Schmidt-Nowara et al., 1984). Though this may be detected clinically it may not be considered significant for two reasons, as in our patients (Colp et al., 1980). First, the stridor is of low volume due to respiratory muscle weakness (Foulkes, 1981); secondly, all therapeutic measures are concentrated on improving the respiratory muscle function. Thus the isolated poor vocal fold abductor function is missed and this can lead to respiratory failure (Schmidt-Nowara etal., 1984). Laryngeal stridor is a life-threatening complication of myasthenia gravis. It should be anticipated in every patient who is either in myasthenic crisis or respiratory distress.
Case 1 A 55-year-old woman presented to the ENT department with a sudden onset of stridor and dysphagia of two days duration. On indirect laryngoscopy, both vocal folds were in the paramedian position. No other laryngeal abnormalities were detected. Emergency measures for the stridor were not instituted, as at the time of examination this was only mild and a sufficient gap was seen between the vocal folds to allow adequate ventilation. A physician was called in to see the patient, who detected that she had bilateral ptosis, external opthalmoplegia and moderate weakness of all four limbs and myasthenia was suspected. It was further ascertained that this patient had been experiencing progressive weakness of proximal muscles for two months. While being admitted to the ward for a detailed evaluation, she suddenly had a respiratory arrest. She was immediately resuscitated and a tracheostomy was performed after which she was ventilated as her breathing was inadequate. A positive edrophonium test confirmed the diagnosis of myasthaenia gravis and she was started on treatment. However, she subsequently developed respiratory infection, septicaemia and died. Case 2 A 38-year-old lady, known to have myasthenia gravis and on
Accepted for publication: 18 March 1992 633
634 References Colp, C, Kriplani, L., Nussbaum, N. (1980) Vocal cord paralysis in myasthenia gravis following anaesthesia. Chest, 77: 218-220. Foulkes, C. J. (1981) Myasthenia gravis presenting as laryngeal stridor after exposure to chlorine gas. Southern Medical Journal, 74: 1423-1424. Friedman, S., Goffin, F. B. (1966) Abductor cord vocal weakness in myasthenia gravis. Report of a case. Laryngoscope, 76: 1520-1523. Gal, T. J., Aurora, N. S. (1982) Respiratory mechanics in supine subjects during progressive partial curarization. Journal of Applied Physiology, 52: 57-63. Neal, G. D., Clarke, L. R. (1987) Neuromuscular disorders. Otolaryngologic Clinics of North America, 20 (1): 195-201.
A. JOB, R. RAMAN, C. GNANAMUTHU
Schmidt-Nowara, W. W., Marder, E. J., Feil, P. A. (1984) Respiratory failure in myasthenia gravis due to vocal cord paresis. Archives of Neurology, 41: 567-568. Address for correspondence: R. Raman, Professor and Head, Department of ENT, Christian Medical College and Hospital, Ida Scudder Road, Post Box No. 3, Vellore-632 004, Southern India.
Key words: Respiratory sounds, stridor; Myasthenia gravis
