The Tensilon test is a method to help diagnose myasthenia gravis.

The drug Tensilon is slowly given through an intravenous line. The health care provider may want to fatigue your muscles by having you do various exercises such as counting until your voice diminishes or holding your arms above your shoulders until they drop. The rest of the Tensilon is then given.

You will be asked to perform some repetitive muscular movements like crossing and uncrossing your legs with particular attention paid to whether your muscle strength is improved by the Tensilon.

The test may be repeated and additional Tensilon may be given to help tell the difference between myasthenia gravis and other conditions.

No special preparation is usually necessary. However, you should follow any dietary restrictions or other directions prescribed by your health care provider.

There will be a sharp prick as the IV needle is inserted. There may be some side effects from the drug.

The test helps diagnosis myasthenia gravis, may aid in telling the difference between myasthenic and other similar neurological conditions, and may be used to monitor oral anticholinesterase therapy.

In myasthenia gravis, the muscles will improve immediately following the Tensilon. The maximum benefit only lasts several minutes.

In myasthenic crisis (worsening of the disease that requires anticholinesterase therapy), there is a brief improvement in the muscle strength.

In cholinergic crisis (overdose of anticholinesterase), Tensilon will exaggerate the muscle weakness.

Additional conditions under which the test may be performed include Lambert-Eaton syndrome.

The risks are side effects from the drug, including respiratory failure.