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Superficial anterior muscles |
Alternative names
Myasthenic syndrome
Definition
Lambert-Eaton syndrome is a
condition characterized by muscle weakness that
improves with continued contraction of the muscle.
Causes
and risks
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 to the receptors of the
neurotransmitter (acetylcholine), Lambert-Eaton
syndrome 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 as a paraneoplastic syndrome
or with autoimmune disorders.
Prevention
There is no known prevention.
Symptoms
- Vision changes
- Double vision
- Difficulty maintaining steady gaze
- Swallowing difficulty, gagging or choking
- Weakness/paralysis that varies in amount
- Drooping head
- Poor posture
- Difficulty climbing stairs
- Difficulty lifting objects
- Need to use hands to arise from sitting
or lying positions
- Difficulty talking
- Difficulty chewing
Note: Symptoms are less prominent than those of
myasthenia gravis.
Additional symptoms that may be associated with
this disease:
- Muscle contractions
- Muscle atrophy
- Mouth sores
- Hoarseness or changing voice
- Fatigue
- Facial paralysis
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 is a noticeable improvement of function.
EMG and nerve conduction velocity tests confirm
the diagnosis, with improved function as contraction
is prolonged or with repetitive stimulation.
Treatment
The goal of treatment is to improve muscle strength
and treat tumors or other underlying disorders.
Plasmapheresis, where blood plasma is removed
and replaced with fluid, may improve symptoms
for some people.
Prednisone or other medications that suppress
the immune response may improve symptoms for some
people. Medications may include anticholinesterase
medications such as Neostigmine or Pyridostigmine.
The response is varies.
Prognosis
Symptoms of Lambert-Eaton syndrome
may improve with treatment. However, not all people
respond well to treatment. |
