The Tensilon Test
Acetylcholine is a neurotransmitter chemical that nerve cells release to stimulate your muscles. People with a chronic disease called myasthenia gravis don’t have normal reactions to acetylcholine. Antibodies attack their receptors for acetylcholine, which prevents muscles from being stimulated and makes muscles tired.
The Tensilon test uses the drug Tensilon (generic name: edrophonium) to diagnose myasthenia gravis. Tensilon prevents the breaking down of the chemical acetylcholine, which then helps stimulate the muscles. A patient has myasthenia gravis if his or her muscles get stronger after being injected with Tensilon.
Uses for Tensilon Test
Your doctor might order the Tensilon test if he or she suspects that you have myasthenia gravis. You also may have the test to monitor your dosage of Tensilon or another anticholinesterase drug if you have already been diagnosed. Anticholinesterase drugs work by preventing the breakdown of acetylcholine in individuals with myasthenia gravis.
Symptoms that your myasthenia gravis has worsened, or you have overdosed on the medication include labored breathing and extremely weak muscles. The Tensilon test helps your doctor determine the proper course of treatment.
The Tensilon Test Procedure
Your doctor might set dietary restrictions or tell you to discontinue certain medications or supplements before the test. Let your doctor know exactly what medications you are taking, including herbs. Some can interfere with your test results.
The test will start with an intravenous (IV) needle into your arm or the back of your hand. A small amount of Tensilon will then be injected. Your stomach might feel upset or your heart rate will increase from the drug. Depending on why the test is being administered, it will proceed in different ways.
Myasthenia Gravis Diagnosis
If your doctor suspects you have myasthenia gravis, he or she will tell you to perform a repetitive movement to test your muscles. This may be:
- getting up and down from your chair
- crossing and uncrossing your legs
- holding your arms overhead until they get tired
- counting backwards from 100 until your voice starts to weaken
Each time you get tired, you will get another dose of Tensilon. You might get three or four shots of the drug. The doctor of nurse will note each time whether the shot revives your strength. If so, you may be diagnosed with myasthenia gravis. Your doctor might also administer another anticholinesterase drug called neostigmine (Prostigmin) to confirm the diagnosis.
Tensilon Overdose and Disease Progression
If your doctor is trying to determine whether you’ve overdosed on Tensilon or if your disease is getting worse, he or she will inject a little Tensilon and see what happens. Depending on the results, you’ll be given an additional drug (either neostigmine or atropine) to stabilize you.
Each of these procedures should take about 15 to 30 minutes.
Results of Tensilon Test
Your doctor should be able to tell you the test results right away. You will probably be put on anticholinesterase drug therapy if you are diagnosed with myasthenia gravis. However, your doctor might want you to take additional tests to confirm the diagnosis.
If your doctor was trying to determine whether you overdosed on medication or if your condition has worsened, the test will immediately provide the answer. If an injection of Tensilon temporarily boosts your strength, the myasthenia gravis has gotten worse and you will need further treatment. If the Tensilon injection makes you even weaker, then you have too much anticholinesterase medication in your system.
Anticholinesterase medication is taken when necessary. There is no fixed dosage. This is because the symptoms of myasthenia gravis can vary each day due to factors such as stress and weather. This makes an unintended overdose more likely. Reducing your dosage or frequency should solve the problem if you experience minimal side effects. Contact your doctor immediately if you are experiencing:
- a noticeable muscular weakness
- difficulty swallowing
- respiratory problems
Risks of Tensilon Test
The Tensilon test is associated with a number of common side effects. Fortunately, these usually last for less than a minute. Side effects include:
- upset stomach
- blurred vision
- increased saliva production
- dizziness or fainting
- breathing difficulties
- twitching or rapid, uncontrollable blinking
If you continue to feel unwell, the doctor may give you an injection of atripone. This drug reverses the effects of Tensilon.
In rare cases, the Tensilon test can have serious repercussions, such as breathing failure or abnormal heart rhythms. The test is performed in places where emergency resuscitation equipment is available because of this possibility.
Blood might also accumulate under your skin at the IV site. This clot is called a hematoma. You can apply ice if the clot is large enough to be uncomfortable. Switch to warm compresses after 24 hours. These will help dissolve the hematoma.
People who have a slow heart rate, asthma, an irregular heartbeat, low blood pressure, or obstructions in the urinary tract or intestines might not be good candidates for this test. Your doctor might advise against the Tensilon test if you have sleep apnea—a condition in which you temporarily stop breathing while sleeping.