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A Tensilon test also called an edrophonium test, is a pharmacological test used for the diagnosis of certain neural diseases such as to evaluate myasthenia gravis, which is a neuromuscular condition characterized by muscle weakness. The test will start with an intravenous (IV) needle placed in your arm or the back of your hand. A small amount of Tensilon (edrophonium chloride) will then be injected into your vein the drug usually kicks in within 30 to 45 seconds. The test involves an injection of Tensilon (edrophonium), after which your muscle strength is evaluated to determine whether your weakness is caused by myasthenia gravis or not. Your stomach might feel upset or your heart rate might increase from the drug.
Edrophonium is a rapid-acting anticholinesterase drug of short duration that improves symptoms of myasthenia gravis by inhibiting the breakdown of ACh and increasing its concentration in the neuromuscular junction.
How the Test is Performed
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 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
The test may also be done for conditions such as Lambert-Eaton syndrome.
What Abnormal Results Mean
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.
Risks
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.
