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Respiratory muscle weakness due to neuromuscular disease: Clinical manifestations and evaluation

Scott K Epstein, MD
Section Editors
Jeremy M Shefner, MD, PhD
Polly E Parsons, MD
R Sean Morrison, MD
Deputy Editor
Geraldine Finlay, MD


Respiratory muscle weakness is common among patients who have neuromuscular disease (table 1) [1,2]. It can be acute (eg, Guillain-Barré syndrome), chronic and relapsing (eg, multiple sclerosis, myasthenia gravis), or relentlessly progressive (eg, amyotrophic lateral sclerosis [ALS]).

Regardless of its clinical course, respiratory muscle weakness is a serious problem among patients with neuromuscular disease. It is estimated that 15 to 28 percent of patients with myasthenia gravis and 20 to 30 percent of patients with Guillain-Barré syndrome will require invasive mechanical ventilation [3-5]. Many patients with ALS will die from progressive chronic respiratory failure.

The clinical manifestations and evaluation of respiratory muscle weakness due to neuromuscular disease will be reviewed here. The management and outcome of such patients are discussed separately. (See "Respiratory muscle weakness due to neuromuscular disease: Management".)


Respiratory muscle (inspiratory, expiratory, upper airway) weakness due to neuromuscular disease can cause insufficient ventilation, nocturnal hypoventilation, or ineffective cough [6]. It can also be associated with bulbar dysfunction. Each of these abnormalities has its own related symptoms and signs (table 2).

Insufficient ventilation may induce dyspnea, orthopnea, rapid shallow breathing (tachypnea plus decreased tidal volume), accessory respiratory muscle use, thoracoabdominal paradox (inward motion of the abdomen during inspiration), hypercapnia, or hypoxemia.

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Literature review current through: Nov 2017. | This topic last updated: Jul 13, 2017.
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