Myasthenic crisis: clinical features and precipitating factors

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MG study is going to be completed by the end of Nov. 2006.

Myasthenic crisis: clinical features and precipitating factors

Lukas Jyuhn-Hsiarn Lee, Chih-Chao Yang

Department of Neurology, National Taiwan University Hospital, Taiwan.

重症肌無力併呼吸衰竭之臨床特癥及誘發因子

李俊賢 楊智超

Abstract

Objective To investigate the clinical features of the course and precipitating factors of myasthenic crisis (defined as acute respiratory failure with the need for mechanical ventilation).

Background Myasthenic crisis is a potentially life-threatening complication of myasthenia gravis (MG) and may be precipitated by multiple factors. Identification and prevention of the precipitating factors are important.

Materials and methods We respectively reviewed the medical records of patients with MG admitted due to respiratory failure at a university hospital in Taiwan during December 1983 – September 2005.

Results Twenty three among 432 hospitalized MG patients experienced 34 episodes of myasthenic crisis. Six patients had multiple episodes. Median age at the onset of first crisis was 58 (range 16-89) years with a female predominance (F:M=15:8). The median interval from onset of MG symptoms to first crisis was 6 months (0.03-276). Ten of these patients (43.5%) had thymoma. Twelve patients (52%) developed crisis within 6 months after symptom onset. Five of them had a rapid course with respiratory failure as the initial presentation of MG, four had inadequate treatment or drug withdrawal, and the rest three developed crisis after infection. For the other 11 patients, precipitating factors could be identified as infection in 7, inadequate treatment in 3, and one patient developed crisis after operation. Nine of 12 patients (75%) who developed crisis within 6 months had ocular symptoms such as ptosis and diplopia as the initial presentation; 8 of the other 11 patients (72.7%) had ocular symptoms.

The median duration of MG crisis episodes in terms of hospital stay was 46 days (6-306), and the median intensive care unit stay was 28 days (2-53). Two patients received non-invasive ventilator support with BiPAP. The median period of intubation was 18 days (4-120) and 30 % of our patients received tracheostomy. Four patients died during hospitalization, for an overall mortality of 17.4%. One patients remained ventilator dependent at discharge.

Conclusion Myasthenic crisis can result in prolonged intubation and hospitalization in some patients. Infection, usually pneumonia, and inadequate treatment were the commonest precipitating factor in our series. There was a high percentage of patients developed crisis within 6 months of MG symptom onset. Early diagnosis of MG and adequate treatment are crucial to prevent such serious exacerbations.

Key words: Myasthenia gravis (MG), myasthenic crisis