Lambert-Eaton Myasthenic Syndrome

 

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Lambert-Eaton myasthenic syndrome (LEMS) is an idiopathic or paraneoplastic syndrome producing antibodies against presynaptic voltage-gated P/Q calcium channels. This decreases calcium entry into the presynaptic terminal, which prevents binding of vesicles to the presynaptic membrane and acetylcholine release. LEMS is most often associated with small cell lung cancer, although idiopathic presentations comprise ∼40% of the cases. The most common initial complaint is proximal muscle weakness involving the lower extremities more than the upper extremities. Depressed deep tendon reflexes and autonomic dysfunction are frequently present. Involvement of the bulbar or respiratory muscles is rare. Diagnosis is confirmed by electrophysiological testing, which demonstrates small compound muscle action potentials and facilitation with exercise or 20-Hz repetitive stimulation. A serum test for voltage-gated calcium channel antibodies is commercially available. Treatment involves removing the cancer associated with the disease. If cancer is not found, immunosuppressive medications and acetylcholinesterase inhibitors are used with moderate success. Patients with idiopathic LEMS should be screened every 6 months with chest imaging for cancer.

REFERENCES

• 1 Pascuzzi R. Myasthenia gravis and Lambert-Eaton syndrome.  Ther Apher. 2002;  6 57-68
  PubMedGoogle Scholar
• 2 Lambert E, Eaton L, Rooke E. Defect of neuromuscular conduction associated with malignant neoplasm.  Am J Physiol. 1956;  187 612-613
  PubMedGoogle Scholar
• 3 Gutmann L, Crosby T, Takamori M, Martin J. The Eaton-Lambert syndrome and autoimmune disorders.  Am J Med. 1972;  53 354-356
  CrossrefPubMedGoogle Scholar
• 4 O'Neill J, Murray N, Newsom-Davis J. The Lambert-Eaton myasthenic syndrome.  Brain. 1988;  111 577-596
  PubMedGoogle Scholar
• 5 Motomura M, Hamasaki S, Nakane S, Fukuda T, Nakao Y K. Apheresis treatment in Lambert-Eaton myasthenic syndrome.  Ther Apher. 2000;  4 287-290
  CrossrefPubMedGoogle Scholar
• 6 Sutton I, Winer J. The immunopathogenesis of paraneoplastic neurological syndromes.  Clin Sci. 2002;  102 475-486
  PubMedGoogle Scholar
• 7 Keesey J. Electrodiagnostic approach to defects of neuromuscular transmission.  Muscle Nerve. 1989;  12 613-626
  CrossrefPubMedGoogle Scholar
• 8 Takamori M, Maruta T, Komai K. Lambert-Eaton myasthenic syndrome as an autoimmune calcium-channelopathy.  Neurosci Res. 2000;  36 183-191
  CrossrefPubMedGoogle Scholar
• 9 Engel A. Review of evidence for loss of motor nerve terminal calcium channels in Lambert-Eaton myasthenic syndrome.  Ann N Y Acad Sci. 1991;  635 246-258
  PubMedGoogle Scholar
• 10 Squire M, Chalk C, Hilton-Jones D, Mills K, Newson-Davis J. Type 2 fiber predominance in Lambert-Eaton myasthenic syndrome.  Muscle Nerve. 1991;  14 625-632
  PubMedGoogle Scholar
• 11 Lennon V, Kryzer T, Griesmann G et al.. Calcium-channel antibodies in the Lambert-Eaton syndrome and other paraneoplastic syndromes.  N Engl J Med. 1995;  332 1467-1474
  CrossrefPubMedGoogle Scholar
• 12 Wirtz P, Sotodeh M, Nijnuis M et al.. Difference in distribution of muscle weakness between myasthenia gravis and the Lambert Eaton myasthenic syndrome.  J Neurol Neurosurg Psychiatry. 2002;  73 766-768
  CrossrefPubMedGoogle Scholar
• 13 Barr C, Claussen G, Thomas D, Fesenmeier J, Pearlman R, Oh S. Primary respiratory failure as the presenting symptom in Lambert-Eaton myasthenic syndrome.  Muscle Nerve. 1993;  16 712-715
  PubMedGoogle Scholar
• 14 Eaton L, Lambert E. Electromyography and electric stimulation of nerves in diseases of motor units; observations on myasthenic syndrome associated with malignancy.  J Am Med Assoc. 1957;  163 1117-1124
  PubMedGoogle Scholar
• 15 Johnston I, Lang B, Leys K, Newsom-Davis J. Heterogeneity of calcium channel autoantibodies detected using a small-cell lung cancer line derived from a Lambert-Eaton myasthenic syndrome patient.  Neurology. 1994;  44 334-338
  PubMedGoogle Scholar
• 16 Oh S, Kim D, Head T, Claussen G. Low-dose guanidine and pyridostigmine: relatively safe and effective long-term symptomatic therapy in Lambert-Eaton myasthenic syndrome.  Muscle Nerve. 1997;  20 1146-1152
  CrossrefPubMedGoogle Scholar

Michael MareskaM.D. 

Department of Neurology, Robert C. Byrd Health Sciences Center, West Virginia University

One Medical Center Drive, Morgantown, WV 26506-9108