Lambert Eaton Myasthenic Syndrome

• Lambert-Eaton myasthenic syndrome is an autoimmune condition affecting the neuromuscular junction, similar to myasthenia gravis.
• The symptoms of Lambert-Eaton myasthenic syndrome tend to be more insidious and less pronounced than myasthenia gravis.
• In most cases, Lambert-Eaton myasthenic syndrome is a paraneoplastic syndrome occurring alongside small-cell lung cancer (SCLC).
• Lambert-Eaton myasthenic syndrome can occur as a primary autoimmune disorder without the presence of SCLC.
• The pathophysiology of Lambert-Eaton myasthenic syndrome results from antibodies against voltage-gated calcium channels.
• These antibodies may be produced in response to small-cell lung cancer (SCLC) cells that express voltage-gated calcium channels.
• Reflexes may be absent in a rested patient but be present when testing immediately after the patient maximally contracts the associated muscles.
• Excluding underlying malignancy, such as small-cell lung cancer, is essential in the management of Lambert-Eaton myasthenic syndrome.
• Other options for the management of Lambert-Eaton myasthenic syndrome include Pyridostigmine (cholinesterase inhibitor), immunosuppressants (e.g., prednisolone or azathioprine), IV immunoglobulins, plasmapheresis, and physical therapy.
• When the voltage-gated calcium channels are destroyed, less acetylcholine is released into the synapse, resulting in a weaker signal and reduced muscle contraction.
• Signs and symptoms of Lambert-Eaton myasthenic syndrome improve after periods of muscle contraction, which is the reverse of what is seen in myasthenia gravis.
• Muscle strength may improve after use in Lambert-Eaton myasthenic syndrome.
• Amifampridine works by blocking voltage-gated potassium channels in the presynaptic membrane, which in turn prolongs the depolarisation of the cell membrane and assists calcium channels in carrying out their action.
• Acetylcholine travels across the synapse and attaches to receptors on the postsynaptic membrane, simulating muscle contraction.
• Autonomic dysfunction, causing dry mouth, blurred vision, impotence and dizziness, is a common feature of Lambert-Eaton myasthenic syndrome.
• Reduced or absent tendon reflexes are also a feature of Lambert-Eaton myasthenic syndrome.
• Voltage-gated calcium channels are responsible for assisting in the release of acetylcholine into the synapse of the neuromuscular junction.
• Lambert-Eaton myasthenic syndrome targets and damages voltage-gated calcium channels in the presynaptic membrane of the neuromuscular junction.
• The key presenting features of Lambert-Eaton myasthenic syndrome are proximal muscle weakness, causing difficulty climbing stairs, standing from a seat or raising the arms overhead.