Lambert-Eaton myasthenic syndrome (LEMS) is a rare neuromuscular junction disorder of paraneoplastic or primary autoimmune etiology.
LEMS is the second most common neuromuscular junction disease after myasthenia gravis.
The most common clinical feature is progressive proximal leg weakness. Deep tendon reflexes are almost always decreased. A less prominent but characteristic feature is autonomic dysfunction, most commonly dry mouth. Less common features include oropharyngeal and ocular symptoms related to weakness, such as dysphagia, dysarthria, ptosis, and diplopia.
The diagnosis is confirmed by electrodiagnostic studies and serology. Specifically, repetitive nerve stimulation demonstrates an increase in compound muscle action potential after increasing the stimulation frequency or after exercise, a phenomenon known as postactivation facilitation. Antibodies against the P/Q-type voltage-gated calcium channel are relatively specific for the diagnosis.
A diagnosis of LEMS should prompt a search for an underlying malignancy, at least including chest CT, with additional consideration of FDG-PET 4.5. These studies most commonly reveal a tumor corresponding to small cell lung carcinoma.
- 1. Titulaer MJ, Lang B, Verschuuren JJ. Lambert-Eaton myasthenic syndrome: from clinical characteristics to therapeutic strategies. (2011) The Lancet. Neurology. 10 (12): 1098-107. doi:10.1016/S1474-4422(11)70245-9 - Pubmed
- 2. Pelosof LC, Gerber DE. Paraneoplastic syndromes: an approach to diagnosis and treatment. Mayo Clin. Proc. 2010;85 (9): 838-54. doi:10.4065/mcp.2010.0099 - Free text at pubmed - Pubmed citation
- 3. Kesner VG, Oh SJ, Dimachkie MM, Barohn RJ. Lambert-Eaton Myasthenic Syndrome. (2018) Neurologic clinics. 36 (2): 379-394. doi:10.1016/j.ncl.2018.01.008 - Pubmed
- 4. Titulaer MJ, Wirtz PW, Willems LN, van Kralingen KW, Smitt PA, Verschuuren JJ. Screening for small-cell lung cancer: a follow-up study of patients with Lambert-Eaton myasthenic syndrome. (2008) Journal of clinical oncology : official journal of the American Society of Clinical Oncology. 26 (26): 4276-81. doi:10.1200/JCO.2008.17.5133 - Pubmed
- 5. Titulaer MJ, Soffietti R, Dalmau J, Gilhus NE, Giometto B, Graus F, Grisold W, Honnorat J, Sillevis Smitt PA, Tanasescu R, Vedeler CA, Voltz R, Verschuuren JJ. Screening for tumours in paraneoplastic syndromes: report of an EFNS task force. (2011) European journal of neurology. 18 (1): 19-e3. doi:10.1111/j.1468-1331.2010.03220.x - Pubmed