A drug called Tensilon (also called edrophonium) or a dummy medicine (inactive placebo) is given during this test. The health care provider gives the medicine 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 getting the drug.
You will be asked to perform some muscle movements over and over again, such as crossing and uncrossing your legs or getting up from a sitting position in a chair. The health care provider will check whether the Tensilon improves your muscle strength. If you have weakness of the eye or face muscles, the effect of the Tensilon on this will also be monitored.
The test may be repeated and you may have other Tensilon tests 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:
Diagnose myasthenia gravis
Tell the difference between myasthenia gravis and other similar brain and nervous system conditions
Monitor treatment with oral anticholinesterase drugs
In many patients with myasthenia gravis, the muscles will improve right after the Tensilon. The maximum benefit only lasts a few minutes. For some types of myasthenia, Tensilon can make the weakness worse.
When the disease gets worse enough to need treatment (myasthenic crisis), there is a brief improvement in muscle strength.
When there is an overdose of anticholinesterase (cholinergic crisis), Tensilon will make the person even weaker.
What the risks are
The drug used during the test may cause side effects, including fainting or breathing failure. That is why the test must be done in a medically supervised setting.
Sanders DB, Howard JF Jr. Disorders of neuromuscular transmission. In: Bradley WG, Daroff RB, Fenichel GM, Jankovic J, eds. Bradley: Neurology in Clinical Practice. 5th ed. Philadelphia, Pa: Butterworth-Heinemann Elsevier; 2008:chap 82.
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.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by Joseph V. Campellone, MD, Division of Neurology, Cooper University Hospital, Camden, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.