Lambert-Eaton myasthenic syndrome

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

Case history #1

A 62-year-old man presents with a 6-month history of generalized fatigue and weakness. He initially noted difficulty ascending stairs and a "metallic" taste in his mouth. Over the past several months, he has also had an unintentional 40 kg weight loss and developed intermittent dysarthria, difficulty raising his arms above his head, and impotence. He is a cigarette smoker with a 60-pack/year history. Exam reveals a cachectic man with poorly reactive, dilated pupils and mild bifacial weakness. Prominent weakness in the pelvic and shoulder girdles with mild distal leg weakness is noted. Reflexes are initially absent, although these are obtainable after a brief period of exercise.

Case history #2

A 38-year-old woman with a history of Hashimoto thyroiditis presents with a 2-year history of generalized fatigue and weakness. She initially had mild difficulty walking prolonged distances that she attributed to deconditioning. She has noted that she seems to "waddle" when she walks. She has developed constipation over the same period. Her eyes are dry, and she also complains of a "dry mouth." She is being treated for hypothyroidism, and her mother has rheumatoid arthritis. Exam reveals minimally greater pelvic than shoulder girdle weakness. Tendon reflexes are difficult to elicit, but improve after a brief period of exercise. She was initially suspected to have myasthenia gravis, and she was treated with oral pyridostigmine bromide. This did not produce significant improvement in the weakness, although her sensation of dry eyes improved.

Other presentations

The clinical features of Lambert-Eaton myasthenic syndrome (LEMS) can include the triad of proximal muscle weakness, areflexia, and autonomic dysfunction.[2] Although the time course to develop these features is variable, proximal lower extremity weakness is almost always the initial symptom. Rapid development of additional symptoms of weakness and autonomic dysfunction within 6 months is highly suggestive of LEMS in association with an underlying cancer (CA-LEMS).[1] Ocular symptoms are rare, and may be a late manifestation. Myasthenia gravis/LEMS overlap syndromes with clinical, electrophysiologic, and serologic features of both disorders have been described, although they are rare.[3] In rare circumstances of severe disease, patients may present with neuromuscular respiratory failure, which may require mechanical ventilation.

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