Atypical Presentation of Lambert Eaton Myasthenic Syndrome

Abstract

SESSION TITLE: Critical Care 3 SESSION TYPE: Affiliate Case Report Poster PRESENTED ON: Tuesday, October 31, 2017 at 01:30 PM - 02:30 PM INTRODUCTION: Lambert-Eaton Myasthenic Syndrome (LEMS) is a rare disorder in which antibodies against presynaptic voltage-gated calcium channels (VGCC) prevent the flux of calcium into the nerve terminal. This reduces the release of acetylcholine affecting neuromuscular transmission. Here we discuss an atypical presentation of LEMS. CASE PRESENTATION: A 64 year old male was admitted for dysphagia and difficulty ambulating. Chest x-ray showed a mediastinal mass. CT confirmed a 5 x 5 cm anterior mediastinal mass. He had 4/5 strength and 1+ deep tendon reflexes (DTRs) in lower extremities. Sodium was 119 mEq/L. On day 2, the patient had bradycardic arrest. Return of spontaneous circulation was achieved after 3 minutes of chest compressions and he was intubated. During his hospital course, he had tachybradyarrhythmias. Despite immediate recovery to his normal mental status, normal chest x-ray, and arterial blood gas, he continued to fail his spontaneous breathing trials. He had a negative inspiratory force of -6 and vital capacity of 150 mL. Paraneoplastic syndrome was suspected due to neuromuscular respiratory failure, hyponatremia, and mediastinal mass. Intravenous immunoglobulin (IVIG) was given for 5 days. On day 10 of intubation, supraclavicular lymph node biopsy showed small cell lung carcinoma and carboplatin and etoposide was initiated. The patient was extubated on the same day. Serology was positive for P/Q type VGCC antibodies. DISCUSSION: LEMS has a prevalence of 2.3 per million and an incidence of 0.5 per million. There have been 400 reported LEMS cases in the US, of which 17 cases had frank respiratory failure. Sixty percent of LEMS cases are associated with small cell lung cancer. Patients with LEMS have proximal muscle weakness that transiently improves after repetitive exertion, absent DTRs, bulbar dysfunction, and autonomic dysfunction. This patient had dysphagia, a sign of bulbar dysfunction. He ambulated while intubated, which may reflect improvement of weakness after repetitive exertion. If not, this level of weakness is uncommon in LEMS as diaphragmatic weakness often parallels the degree of proximal muscle weakness. In contrast to other cases in which DTRs are absent, this patient had hyporeflexia. Finally, he had dysautonomia manifesting as fluctuating episodes of bradycardia and tachycardia. EMG is used to confirm LEMS, however was not available. CONCLUSIONS: Neuromuscular respiratory failure should lead to evaluation of more common causes of weakness. In patients with malignancy, the possibility of LEMS should be entertained. The early use of IVIG in this patient allowed for earlier extubation. Reference #1: Laghi F, et al. Disorders of the respiratory muscles. Am J Respir Crit Care Med. 2003. 168(1): 10-48. Reference #2: Bekircan-Kurt C, et al. Voltage gated calcium channel antibody-related neurological diseases. World J of Clin Cases: 3.3 (2015): 293. Reference #3: Sanders DB. Lambert-eaton myasthenic syndrome: diagnosis and treatment. Ann NY Acad Sci. 2003. 998: 500-508. DISCLOSURE: The following authors have nothing to disclose: Gauri Behari, Raja Sinha, Vadym Rusnak, Andrea Espinoza, Michael Charlet, Ibrahim El-Abbassi No Product/Research Disclosure Information