Intravenously, edrophonium chloride Tensilon (r) is a short-acting medication. If your weakness, particularly in the eye muscles, improves momentarily and temporarily, you may have MG. If this effect occurs quickly, within minutes, of injecting edrophonium into your vein, it is called a "positive twitch test." This means that you have myasthenia gravis. If you do not show any improvement in your muscle strength or feel any side effects from the drug, this means that you do not have MG. The test cannot tell whether you are truly weak because you are trying to be nice or if you really are unable to move some muscles due to other problems, such as multiple sclerosis or muscular dystrophy. The test can only diagnose you with myasthenia gravis; it cannot cure you of this disease. Edrophonium testing is used to help doctors choose the right treatment for you. It may also be useful in monitoring your response to therapy. Tensilons are injected into a large vein in your arm or leg. Myasthenia Gravis is a disease in which the body's immune system attacks the nerves that control movement. The result is weakness of the face, neck, arms, legs, and trunk.