Lambert-Eaton Myasthenic Syndrome

Lambert Eaton Myasthenic Syndrome – Problem of Nerve Signals

Lambert Eaton myasthenic syndrome – LEMS is a rare ailment caused by a problem with the transmission of nerve signals to the muscles. It results in a weakness in the muscle and at times,associated with dryness of the mouth, constipation as well as impotence. It is an autoimmune neuromuscular disorder affecting the presynaptic neuromuscular junction.

The muscle weakness in the case of LEMS is due to auto-antibodies to voltage gated calcium channels at presynaptic area of the neuromuscular junction which leads to a reduction in the quantity of acetylcholine that is released from the nerve terminals. Person suffering from LEMS tend to experience fatigue, stiffness and muscle pain and the weakness is more pronounced in the lower extremity muscles especially in the legs and hip girdle areas.

Other problems may include reduced reflexes, drooping of the eyelids, problems in swallowing and facial weakness besides dry mouth, constipation and impotence. In some rare cases, these problems could be life-threatening when the weakness is related to respiratory muscles.

LEMS - Paraneoplastic/Non-Paraneoplastic

LEMS has two forms where the first type is related to people having cancer, the majority of those having small cell lung cancer – SCLC is related to those who smoke and starts after the age of 50. This form of LEMS is known as paraneoplastic.

 Fifty percent of the cases of LEMS are triggered due to underlying lung cancer which is associated with smoking and the person usually tends to develop this disease during middle or at a later age. In the other form of this disease, there is no tumour and this condition tends to start after the age of 40 though it could also start in children under the age of 10 which is known as non-paraneoplastic LEMS.

The immune system tends to mistakenly attack the nerve endings resulting in weakening the nerve impulses from the nerves to the muscles, thus preventing the muscles from contracting or tightening properly.The first symptom of LEMS is weakness in the leg with difficulty in walking. Oculobulbar weakness which affects the muscles of the eyes, face and throat could develop later, causing droopy eyelids or ptosis, speech impairment together with problem in swallowing.

LEMS Can be Controlled

For diagnosis, a special kind of blood test is conducted to detect the antibodies which may damage the nerve endings where these antibodies do not show up in people without LEMS. Nerve conduction test which involves electromyography, a procedure which is used to identify communication problem between the nerves and muscles is done, where a needle electrode is inserted through the skin in the muscle.

 This produces an electrical recording on the activity of the muscle and if the person suffers from LEMS, the muscles tend to fail in responding to the electrical stimulation. Besides this, a nerve stimulation test is also carried out which shows whether the transmission of signals between the nerve and muscle is poor or not. Those diagnosed with LEMS should first be investigated for any possibility of cancer and if found with cancer, they should first be treated for the removal of cancer which could improve the symptoms.

Though LEMS cannot be cured, its symptoms can be controlled by stimulating a great amount of acetylcholine, by prolonging the activity of the acetylcholine which is released and by reducing the levels of the antibodies caused by the condition.