Syndrome of Inappropriate Antidiuretic Hormone Secretion Associated with Amyotrophic Lateral Sclerosis in a Patient Developing Carbon Dioxide Narcosis

Abstract

We report a rare case of syndrome of inappropriate antidiuretic hormone secretion (SIADH) associated with amyotrophic lateral sclerosis (ALS). A 69-year-old man was admitted to our hospital with sustained hyponatremia. Hyposmolality with elevated urinary osmolality and sodium excretion was observed, which indicated SIADH. The treatment for SIADH was challenging; the patient developed carbon dioxide narcosis, which led to the diagnosis of ALS. After the initiation of noninvasive positive-pressure ventilation, the patient's serum sodium concentration normalized and became stable. Thus, ALS should be recognized as a possible cause of SIADH in the clinical setting.

Figure 1.

Chest computed tomography (CT) obtained during the patient’s first admission to our hospital. CT showed no emphysematous changes or space-occupying lesions.

Figure 2.

The clinical course, laboratory data, and treatment of the present case. CO₂: carbon dioxide, NPPV: non-invasive positive pressure ventilation

Figure 3.

Chest radiographs of the inspiratory and expiratory phases of breathing. Bilateral movement of the diaphragm was only observed between one intercostal margin.

Figure 4.

Progressive atrophy of the paraspinal and rotator cuff muscles.