Lambert-Eaton syndrome

Lambert-Eaton myasthenia is a presynaptic myasthenic syndrome characterised by impaired release of acetycholine from nerve terminals. (1,2)

• Lambert-Eaton myasthenic syndrome (LEMS) is a neuromuscular junction disorder characterized by fluctuating proximal limb muscle weakness, decreased deep-tendon reflexes, and various autonomic symptoms
  • most frequently associated with small-cell lung cancer (SCLC)
    • 60% of patients have small cell lung carcinoma.
  • aetiology of LEMS is the reduced exocytosis of acetylcholine from nerve endings by antibodies against voltage-gated calcium channels (VGCC-abs)
    • increases in the titres of which are observed in more than 90% of patients with LEMS
  • been reported that titer of muscle anti-acetylcholine-receptor-binding antibodies (AChR-abs), which are more specific for myasthenia gravis (MG), is also increased in a small percentage of patients with LEMS (7%)

The usual age of onset in between 50 and 60 years of age. Men are affected more than women.

Electromyography shows increased evoked potentials after repeated galvanic stimulation (the opposite occurs in myasthenia gravis).

The autoimmune aetiology of Eaton-Lambert should be compared and contrasted with myasthenia gravis.

Reference:

1. Graus F et al. Updated Diagnostic Criteria for Paraneoplastic Neurologic Syndromes. Neurol Neuroimmunol Neuroinflamm. 2021 Jul;8(4)
2. Pascuzzi RM, Bodkin CL. Myasthenia Gravis and Lambert-Eaton Myasthenic Syndrome: New Developments in Diagnosis and Treatment. Neuropsychiatr Dis Treat. 2022;18:3001-3022