Lambert-Eaton Syndrome or Eaton-Lambert Syndrome

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What is Lambert-Eaton Syndrome or Eaton-Lambert Syndrome?

Lambert-Eaton syndrome is a disease of the neuromuscular junction. A syndrome is a constitution of symptoms or conditions that occur together with the clinical significance that there may be presence of a certain disease.

Lambert-Eaton syndrome is a disease that is characterised by muscle weakness that improves with continued contraction of the muscle.

Lambert-Eaton syndrome is also known as Eaton-Lambert syndrome or Lambert-Eaton myasthenic syndrome because of the close similarity to another disease called myaesthenia gravis.

Lambert-Eaton syndrome affects the muscle and also the autonomic nervous system. Autonomic nervous system controls the involuntary part of the nerve system, for example, sweating mechanism, salivation, gut movement, and sexual function (erection).

Who gets Lambert-Eaton Syndrome or Eaton-Lambert Syndrome?

Lambert-Eaton syndrome is considered to be an extremely rare condition. The true number of cases of Lambert-Eaton syndrome is unknown. It is associated with 3% of patients with a fatal and rapidly destructive form of lung cancer, called small cell lung cancer, and this equates to 4 in 1 million of the population in the United States.

However, this figure excludes the population that has Lambert-Eaton syndrome without small cell lung carcinoma.

Predisposing Factors

This is a disease of the middle aged to elderly population, which may be due to the association of small cell lung cancer (a disease of the middle aged to elderly).

However, case reports documented that Lambert-Eaton syndrome had occurred in children younger than 17 years old.

There is no gender predilection in Lambert-Eaton syndrome although small cell lung carcinoma is more common in men.

Progression

Lambert-Eaton syndrome is a disease of the neuromuscular junction, i.e. the junction of the nerve ending and muscle fibre. It can be considered as an autoimmune disease. For normal muscle contraction, the nerve ending will release a biochemical substance called acetylcholine (ACh), which then binds to the motor fibre and stimulate contraction. In Lambert-Eaton syndrome, the nerve fibre is unable to release adequate ACh, resulting in weak muscle contraction.

It is thought that in small cell lung cancer, the body's immune system is activated and hence leading to the above changes.

The significance of this syndrome is the association with small cell lung cancer, the most fatal and rapidly progressing of lung cancers. Approximately 50-60% of the patients with Lambert-Eaton syndrome have this association. The diagnosis of Lambert-Eaton syndrome may suggest the presence of the tumour long before it would otherwise be detected, allowing early removal.

Other cancers associated with Lambert-Eaton syndrome include lymph node cancers, thymus cancer, bladder cancer, and cancers of the major organs.

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