A medicine 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 medicine called atropine before receiving Tensilon so that you do not know you are getting the medicine.
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 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. Follow your provider's instructions about how to prepare.
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 people with myasthenia gravis, the muscles will improve right after the Tensilon. The improvement lasts only 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.
The medicine used during the test may cause side effects, including fainting or breathing failure. This is why the test is done by a health care provider in a medical setting.
Huff JS. Special neurologic tests and procedures. In: Roberts JR, Hedges JR, eds. Roberts and Hedges' Clinical Procedures in Emergency Medicine. 6th ed. Philadelphia, PA: Elsevier Saunders; 2014:chap 61.
Amit M. Shelat, DO, FACP, Attending Neurologist and Assistant Professor of Clinical Neurology, SUNY Stony Brook, School of Medicine, Stony Brook, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.