Lambert-Eaton Syndrome

Lambert-Eaton syndrome is an autoimmune disease, which also belong to paraneoplastic syndromes. The term “paraneoplastic” means that it may occur when there is a cancer present in the body. Specifically, the Lambert-Eaton syndrome occurs in small cell lung cancer. On the other hand, the syndrome may be detected as a separate disease without any tumor present.

Causes

The cause of the syndrome is formation of aggressive antibodies that attack our own tissues. In case of Lambert-Eaton syndrome the affected tissue is the neuromuscular junction where the nerve signal transmits to muscle fibers. The motoric nerve signal is conducted by nerve fibers to nerve endings. The nerve endings release a substance known as acetylcholine, which binds to receptors of muscle fibers and causes their contractions. Lambert-Eaton syndrome affects the nerve endings and disrupts the release of acetylcholine. The situation results in disruption of neuromuscular junctions and muscle weakness, which is similar to myasthenia gravis (see related text).

Symptoms

The syndrome manifests with severe muscle weakness leading to rapid fatigue. The problems tend to be stronger in the morning and slightly improve during physical activity (which is the exact opposite of myasthenia gravis, where physical exercise significantly worsens the symptoms). Tendon reflexes are also significantly weakened. The syndrome is frequently accompanied with disorder of saliva secretion and dry mouth.

Diagnosis

Patients with abnormal muscle weakness should be examined by a neurologist including the electromyography, which can detect the failure of neuromuscular transmission. Serological methods can prove the presence of specific aggressive autoantibodies in the patient’s blood. Part of the examination process should be exclusion of a malignant tumor in the body, especially a lung tumor (chest X-ray or computed tomography).

Treatment

If the syndrome is tumor-related, it is necessary to cure the tumor, if possible. Removal or suppression of tumor tissue may lead to disappearance of symptoms. The syndrome itself is treated by immunosuppressive drugs, e.g. the corticosteroids.