Diagnosis of Myasthenia Gravis Confirmed with Tensilon Test

Post prepared by Dr Mrugesh Panchani, PGYIII Medicine Resident, Monmouth Medical Center.

For patients with clinical features and signs suggestive of myasthenia gravis, the Tensilon test can serve as an easy bedside confirmatory test.

Edrophonium (Tensilon) is an acetylcholinesterase inhibitor and we have already blogged about how these drugs can improve conduction across the neuromuscular junction in myasthenics.

Tensilon is preferable for diagnostic testing because of the rapid onset (30 s) and short duration (5 min) of its effect.

However, an objective end-point must be selected to evaluate the therapeutic effect, such as improvement in eye movements, ptosis, impairment of speech, or the length of time that the patient can maintain the arms in forward abduction.

Here’s a real life example (we have a signed consent form on file):

The first video shows our patient at her baseline with R>L ptosis and facial weakness:

Then the patient is given a low dose (2mg) of iv Tensilon (with telemetry monitoring and bedside atropine at the ready) is given and we see a definite improvement in ptosis and a more expressionful face:

This test was considered positive and hence terminated.

Had there been no change, the patient would have been given an additional 8 mg of iv Tensilon.

We typically start with a low dose at first because some patients react to edrophonium with side effects such as nausea, diarrhea, salivation, fasciculation, and (rarely) bradycardia. Atropine (0.6 mg) should be drawn up in a syringe, ready for IV administration if these symptoms occur.