[Motor neuron disease with respiratory insufficiency as primary manifestation].

A 66-year-old man with dyspnea on exertion suffered a cardiac arrest and was referred to our hospital after emergency room intubation. Chest X-ray films detected no abnormalities. Blood gas analysis showed hypoxemia with normal A-aDO 2, and pulmonary function tests revealed combined ventilatory impairment. Chest fluoroscopy revealed weakness of diaphragmatic motion. No other abnormalities were found on initial examination. It was difficult to wean the patient off mechanical ventilation and identify the cause of alveolar hypoventilation. On the 60th hospital day, a neurological examination and electromyography disclosed fasciculation and denervation of the left biceps and pectoralis major muscle. These findings supported the diagnosis of motor neuron disease (MND). Although respiratory insufficiency as an initial symptom of MND is unusual, physicians should be aware of the possibility of MND in cases of alveolar hypoventilation of unknown etiology.