Amyotrophic Lateral Sclerosis Presenting as Bilateral Diaphragm Paralysis

Abstract

INTRODUCTION: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that typically presents with progressive muscle weakness. Respiratory symptoms due to diaphragmatic weakness generally occur late in the clinical course. We describe a case of ALS with the rare presentation of diaphragmatic paralysis as the initial manifestation. CASE PRESENTATION: A 69 year old veteran with a past medical history of psoriasis, diabetes mellitus and hypertension was referred to the VA pulmonary clinic with complaints of progressive dyspnea on exertion, hoarseness, and orthopnea. Initial chest radiograph and computed tomography of the chest were notable for subsegmental atelectasis and elevated right hemidiaphragm suspicious for diaphragmatic paralysis. He was subsequently lost to follow-up, but ultimately was admitted to a large community hospital with worsening dyspnea. He was hypoxic, hyperreflexic and was noted to have muscle atrophy in his upper and lower extremities. His chest radiograph showed diminished lung volumes, atelectasis and elevation of both hemidiaphragms. Pulmonary function testing showed severe restrictive disease. Ultrasonography of the diaphragms demonstrated bilateral dysfunction. He returned four months later with continued dyspnea and new-onset muscle fasciculations and bulbar weakness. Electromyography (EMG) was consistent with Amyotrophic Lateral Sclerosis (ALS). DISCUSSION: ALS is a fatal neurodegenerative disease of unknown etiology characterized by progressive muscular paralysis due to degeneration of the upper and lower motor neurons. It generally affects patients between 40 and 60 years of age and is uniformly fatal with a median survival time of 36-48 months from the time of initial diagnosis. Recent reports indicate that veterans are at increased risk of developing ALS. The typical presenting symptoms include dysphagia, limb muscle weakness, muscle cramping and atrophy, or fasciculations. Muscular paralysis is progressive and ultimately advances to involve the diaphragm. Patients may have a restrictive ventilatory defect and hypercapnic respiratory failure. In most cases death occurs from respiratory complications, and the presence of diaphragmatic dysfunction is associated with a marked reduction in survival. A decrease in FEV1 and FVC of more than 20% in the supine position compared to erect position suggests diaphragmatic weakness in ALS. Use of sniff testing with fluoroscopy can be misleading in the presence of bilateral diaphragmatic paralysis. Nerve conduction studies and EMG are the diagnostic tests of choice for ALS. Patients with ALS complicated by respiratory insufficiency have shown prolonged survival and improved quality of life with early use non-invasive positive pressure ventilation. Tracheostomy, diaphragmatic pacing and invasive ventilation can also be offered as supportive therapy. Our case was unique because the patient presented with respiratory complaints and he later developed bulbar palsy and fasiculations. Respiratory symptoms are an unusual presenting manifestation of ALS, and are present in less than 3% of the cases at the time of initial diagnosis. Clinicians should be wary of respiratory onset ALS in patients with diaphragmatic paralysis and dyspnea CONCLUSIONS: Although rare, patients with ALS can present with respiratory symptoms. Given the finding of orthopnea and dyspnea with suspected diaphragmatic paralysis, a thorough neurological evaluation may uncover a diagnosis of ALS.