Myasthenia gravis and respiratory failure related to phrenic nerve lesion
✍ Scribed by Anabela Valadas; Mamede de Carvalho
- Publisher
- John Wiley and Sons
- Year
- 2008
- Tongue
- English
- Weight
- 84 KB
- Volume
- 38
- Category
- Article
- ISSN
- 0148-639X
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✦ Synopsis
A 56-year-old woman was admitted to the intensive care unit due to severe global respiratory failure. Over the 5 days before admission, she progressively developed dyspnea, exercise intolerance, and orthopnea. She had no pain, cough, or fever.
She had been diagnosed as having myasthenia gravis (MG) 12 years earlier. At that time, she had fluctuating dysphagia, dysphonia, ptosis, and diplopia that improved on pyridostigmine. Abnormal repetitive nerve stimulation and serum acetylcholine receptor antibodies supported the clinical diagnosis. No thymoma was found, and thymectomy was not performed. She was asymptomatic for the last 10 years on pyridostigmine (120 mg/day). On admission, we observed orthopnea as well paradoxical respiration in the supine position, associated with arterial desaturation. The patient had no ptosis, diplopia, neck or facial paresis, dysphagia, or dysphonia. Routine blood investigation was normal, including thyroid function, C-reactive protein, and serologic tests for Borrelia, herpes virus, and human immunodeficiency virus. A chest radiograph demonstrated bilateral hemidiaphragm elevation but no other abnormality. Neurophysiological investigation showed normal repetitive nerve stimulation (RNS) of abductor pollicis brevis, trapezius, anconeus, and nasalis, and routine diaphragm compound muscle action potentials (DCMAPs) were absent bilaterally. 1 Needle electromyography (EMG) of the diaphragm showed fibrillation potentials and positive sharp waves on both sides. EMG of the right hemidiaphragm revealed no motor unit potentials (MUPs), but 2 remaining MUPs were observed on the left. Bilateral EMG of sternocleidomastoid, genioglossus, and intercostal muscles was normal. Cervical and thoracic computerized tomography scans and magnetic resonance imaging of the cervical spine and brachial plexus, bilaterally, were normal. Cerebrospinal fluid examination was normal.
Treatment with intravenous immunoglobulin (IVIg; 400 mg/kg/day for 5 days) was not effective, and non-