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
) 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.
- Myasthenia gravis presenting as bilateral acute vocal cord paresis is rare.
- Joint care of patients with a neurologist is essential to optimise medical treatment.
- There are no other cases in the literature of successful decannulation after tracheostomy following both initial presentation and subsequent relapse of vocal cord paresis secondary to myasthenia gravis.