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Myasthenia gravis is a condition rarely seen by otolaryngologists. We present a case of bilateral vocal cord paresis caused by previously undiagnosed myasthenia gravis. A tracheostomy was required after initial presentation and after a relapse. The airway management, neurological diagnosis and medical treatment are discussed.
Myasthenia gravis is an autoimmune condition caused by antibodies to the acetylcholine receptors of the neuromuscular junction. It has an annual incidence of between 0.25 and 2 per 100000 and an estimated prevalence of up to 40 per 100000.1
We describe a case of acute vocal cord palsy requiring tracheostomy in a patient subsequently diagnosed with myasthenia gravis. A literature review has shown 12 other case descriptions of myasthenia gravis focal to the larynx. This is the only case in which a new presentation of myasthenia requiring tracheostomy has survived the initial presentation, a subsequent relapse and has been successfully decannulated.
A 71-year-old man presented to accident and emergency with a 4-day history of rapidly progressive shortness of breath and dysphagia for both solids and liquids. He had stridor, his respiratory rate was 40 and his oxygen saturations were below 70% on air. He was intubated. Laryngeal examination by an ear, nose and throat (ENT) surgeon after intubation was normal. Three days later he was extubated but became short of breath and developed stridor. He was re-intubated and taken to theatre. Examination under anaesthetic showed some minimal supraglottic oedema. Tracheostomy was performed.
Three years earlier he had an isolated episode of dysarthria and dysphasia, which was diagnosed as a transient ischaemic attack. One year later he had intermittent dysphagia. He saw an ENT surgeon who performed flexible laryngoscopy and a barium swallow both of which were normal. The following year he had an episode of diplopia and was found to have an internuclear opthalmoplegia. This resolved. MRI at that time showed some bilateral ischaemic changes and the problems were diagnosed as cerebrovascular disease.
Flexible laryngoscopy 2 days after the tracheostomy showed that the vocal cords were fixed in the paramedian position. On swallow assessment, his larynx was elevating and there was only slight laryngeal penetration of thin fluids. A CT scan of the head, neck and thorax was unremarkable. This was performed to rule out malignancy. There was a gradual improvement in both speech and swallowing. He was allowed home on thickened fluids 3 weeks after admission. The presumed diagnosis at this stage was a cerebrovascular event involving the laryngeal and bulbar muscles.
He was readmitted 1 week later. He had a fluctuating pattern of dysphagia and dysarthria and also developed some diplopia. He had copious tracheal secretions. He never developed peripheral weakness. MRI showed small vessel disease similar to the previous scan. The scan was performed to rule out any new cerebrovascular changes. B12 was found to be low and he was intrinsic factor antibody positive. Treatment for pernicious anaemia was commenced. Eight weeks after the original admission flexible laryngoscopy showed that the vocal cords had minimal movement.
The possibility of myasthenia gravis was considered and anticholinesterase antibodies were positive. He was commenced on pyridostigmine 60 mg twice daily. Two days after this he had improved markedly, with no episodes of aspiration. Flexible laryngoscopy showed that vocal cord function was almost normal. Three days later he was able to be de-cannulated and was discharged from the hospital.
After discharge the patient continued to get symptoms of fatigable dysarthria, dysphagia and diplopia. His pyridostigmine was increased gradually to 60 mg five times daily. Vocal cord check 1 month after discharge showed good movement.
Three months after discharge he was readmitted with stridor and respiratory distress. He had experienced 2 days of dyspnoea. His cords were found to be in midline and oedematous. Emergency tracheostomy was performed. He was also diagnosed with pneumonia. He was commenced on antibiotics and on alternate days prednisolone 5mg. He made a gradual improvement and was discharged 1 month later. His prednisolone was increased gradually to 20 mg on alternate days. Three months after the second tracheostomy, examination of his larynx showed good cord movement. He was successfully decannulated. Electromyography studies were performed, which confirmed the diagnosis.
CT of head, neck and thorax; MRI of head; anticholinesterase antibodies; electromyography.
One year on from the second tracheostomy he remains well with good vocal cord movement.
Acute vocal cord paralysis is a rare but critically important presentation of myasthenia gravis. In a series of 147 myasthenic patients over a 12-year period, six patients had documented abductor paresis and four went on to require tracheostomy.2 There have been 12 individual case descriptions in the world literature concerning vocal cord paresis and myasthenia.
Two cases of undiagnosed myasthenia gravis presented with severe dyspnoeic symptoms requiring tracheostomy similar to this case.3,4 One had a respiratory arrest prior to the emergency tracheostomy but died of respiratory complications shortly afterwards.3 The other patient had an emergency tracheostomy after presenting in respiratory distress. Pyridostigmine and steroids were commenced and there was an initial improvement. Unfortunately the patient had a relapse of the vocal cord paresis and died 6 weeks later.4
Five cases presented with sub-acute dyspnoea, dysphonia or swallowing problems in which vocal cord mobility was found to be impaired.5–9 In each of the cases, myasthenia gravis was subsequently diagnosed and medical treatment was instituted. All the patients recovered without the need for tracheostomy. Two patients were found to have thymomas: one benign8 and one malignant.9 In the latter case, plasma exchange was required prior to thymectomy.
Three cases describe vocal cord paresis in pre-existing myasthenic patients on treatment.3,10,11 One patient went on to require a tracheostomy, which was never decannulated as vocal cord mobility never returned.10 Another patient refused tracheostomy against medical advice.3
Myasthenia with laryngeal features caused by specific precipitants (chlorine12 and suxamethonium13) has been described. Our patient presented with stridor and vocal cord paresis requiring tracheostomy. He was subsequently diagnosed with myasthenia gravis and made a good recovery on oral anticholinesterase treatment. A relapse was treated with tracheostomy and steroids, which again resulted in recovery. The excellent outcome was due to proper and timely provision of emergency and medical care.
Myasthenia gravis usually presents with painless and fatigable weakness. This can be localised to specific muscle groups for many years and, hence, mimic other conditions.1 Any muscle group can be affected. Extra-ocular muscles, muscles of facial expression, mastication, phonation and swallowing are often, but not always, involved in the disorder. Involvement of respiratory muscles is rare but can result in mortality without emergency medical treatment. Its relapsing and remitting course can make it difficult to identify and, in the acute situation, any subtle neurological signs can be easily overlooked.
Vocal cord paresis due to myasthenia gravis is uncommon but critically important. Airway management in these situations is a priority and this patient was rapidly intubated. As a consequence his vocal cord paresis only became apparent at a later stage.
Diagnosis was made by anticholinesterase antibodies. These are positive in 85% of myasthenia patients.1 An edrophonium test may be required to clarify the diagnosis if the antibodies are negative. Electromyography can also be useful.
The recovery of speech and swallowing with the onset of pyridostigmine was very rapid. The patient progressed from dysarthria and an unsafe swallow to decannulation and normal diet within 1 week. Oral anticholinesterase treatments are the first-line treatment in myasthenia. If these are not successful then immunosuppressive medications may be required. In this case, the addition of steroids was required to bring the disease under control. In certain situations plasma exchange may be needed.1 Thymectomy is not of proven benefit in late onset myasthenic patients.
This case demonstrates the importance of myasthenia gravis presenting as an acute emergency through vocal cord paresis. This should be borne in mind in the diagnosis and treatment of patients with vocal cord paresis as it represents a potentially reversible cause.
Competing interests: None.
Patient consent: Patient/guardian consent was obtained for publication.