Lambert-Eaton Syndrome

Alternative names:

myasthenic syndrome

Definition:

A condition characterized by muscle weakness that improves with continued contraction of the muscle.

Causes, incidence, and risk factors:

Lambert-Eaton Syndrome (myasthenic syndrome) is a disorder with symptoms very similar to those of myasthenia gravis. There is muscle weakness associated with disturbed communication between nerves and muscles. Unlike myasthenia gravis, where the neurotransmitter (the chemical that transmits impulses) is blocked because of antibodies, Lambert-Eaton syndrome is caused by a insufficient release of neurotransmitter by the nerve cell. As muscle contraction is continued, the amount of neurotransmitter may build up in sufficient quantities and result in increased strength.

The cause is unknown. The disorder is usually associated with small-cell carcinoma or with autoimmune disorders.

This syndrome is rare. Unlike myasthenia gravis, which affects mostly women, Lambert-Eaton syndrome primarily affects men over the age of 40.