Amyotrophic Lateral Sclerosis-Related Respiratory Failure and Association With Inappropriate Secretion Syndrome of the Antidiuretic Hormone

Abstract

There is an unclear association between the syndrome of inappropriate antidiuretic hormone secretion (SIADH) and amyotrophic lateral sclerosis (ALS), with few reports in the literature. We report the case of an 80-year-old man admitted to our emergency room with asthenia, dysphonia, dysphagia, weight loss, and euvolemic hyponatremia, indicating a SIADH. Posteriorly, the patient also developed respiratory failure, which, in association with the previous clinical presentation, led to the diagnosis of ALS. During her permanence at the hospital, the hyponatremia improved with noninvasive positive-pressure ventilation, and the association between these two identities was made. This case also shows that patients with ALS commonly suffer from chronic respiratory failure and still have a reserved prognosis.

Keywords: amyotrophic lateral sclerosis; hyponatremia; inappropriate secretion of antidiuretic hormone; narcosis; respiratory failure.

Figure 1. Clinical course, laboratory results and treatment evolution during hospitalization

Serum sodium (mmol/L) and pCO₂ (mmHg) arterial blood gas evolution during hospitalization and clinical course and treatment description as below. A - First five days: Patient stop diuretics and started NaCl infusion. B - At 5th day new sodium worsening despite treatment. Clinically euvolemia, SIADH suspicion. Patient started fluid restriction with slightly improvement. C - At 9th day observed hypercapnia coma, starting NPPV with improvement of both CO₂ and Na⁺ levels. D - At 19th day patient developing respiratory failure with severe hypoxemia and slightly worsening hypercapnia, needing invasive ventilation. E - At 27th day extubation to NPPV. For motor neuron disease suspicion at 31th day riluzole was started. Although all effort patient day at 48th.