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Tensilon test

Definition

The Tensilon test is a method to help diagnose myasthenia gravis.

How the test is performed

A drug called Tensilon (also called edrophonium) or a dummy medicine (inactive placebo) is given during this test. The health care provider gives the appropriate one through one of your veins (intravenously, through an IV). You may also be given a medication called atropine before receiving Tensilon so that you do not know you are receiving the drug.

You will be asked to perform some repetitive muscular movements such as crossing and uncrossing your legs or getting up from a sitting position in a chair. Particular attention will be paid to whether your muscle strength is improved by the Tensilon.

The test may be repeated and additional Tensilon may be given to help tell the difference between myasthenia gravis and other conditions.

How to prepare for the test

No special preparation is usually necessary. However, you should follow any dietary restrictions or other directions prescribed by your health care provider.

How the test will feel

You will feel a sharp prick as the IV needle is inserted. The drug may cause a feeling of a churning of the stomach or a slight feeling of increased heart rate, especially if Atropine is not given first.

Why the test is performed

The test helps diagnosis myasthenia gravis, may aid in telling the difference between myasthenic and other similar neurological conditions, and may be used to monitor oral anticholinesterase therapy.

Normal Values

What abnormal results mean

In myasthenia gravis, the muscles will improve immediately following the Tensilon. The maximum benefit only lasts a few minutes.

In myasthenic crisis (worsening of the disease that requires anticholinesterase therapy), there is a brief improvement in the muscle strength.

In cholinergic crisis (overdose of anticholinesterase), Tensilon will make the person even weaker.

Additional conditions under which the test may be performed include Lambert-Eaton syndrome.

What the risks are

The drug used during the test may cause side effects, including fainting or respiratory failure. Therefore the test must be done in a medically supervised setting.

Special considerations

References

Vincent A, Newsom-Davis J. Disorders of neuromuscular transmission. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 448.