Lambert-Eaton Syndrome

Alternative names

Myasthenic syndrome

Definition

Lambert-Eaton syndrome is 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.

In myasthenia gravis, the neurotransmitter acetylcholine (the chemical that transmits impulses between nerves and muscles) is blocked by antibodies to its receptor.

In Lambert-Eaton syndrome, however, the signal distortion is caused by an 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 disorder may be associated with small-cell carcinoma of the lung and other malignancies as a paraneoplastic syndrome or with autoimmune disorders.

Symptoms

• Weakness/paralysis that varies in severity
  o Drooping head
  o Difficulty climbing stairs
  o Difficulty lifting objects
  o Need to use hands to arise from sitting or lying positions
  o Difficulty talking
  o Difficulty chewing
  
• Swallowing difficulty, gagging, or choking
  
• Vision changes
  o Blurry vision
  o Difficulty maintaining steady gaze
  

Additional symptoms that may be associated with this disease:

• Blood pressure abnormalities
  
• Dizziness upon standing
  
• Dry mouth
  

Signs and tests
An examination shows weakness or paralysis that improves with activity. Reflexes may be decreased. There may be muscle atrophy (loss of muscle tissue).

A Tensilon test can be positive. A baseline muscle-strength evaluation is performed. After Tensilon (edrophonium) or other short-acting neurotransmitter is given, there may be a noticeable improvement of function.

EMG and nerve conduction velocity tests may confirm the diagnosis, with improved function as contraction is prolonged or with repetitive stimulation.

Treatment

The primary goal of treatment is to identify and treat any tumors or other underlying disorders. Plasmapheresis, where blood plasma is removed and replaced with fluid, may improve symptoms.