Myasthenia Gravis is an autoimmune disease characterized by muscle weakness and fatigability. It is caused by a reduction in the number of acetylcholine receptors at the neuromuscular junction.

      The striking feature of  Myasthenia Gravis is the variability in the weakness of the affected muscles. Weakness varies from day to day and from hour to hour, typically increasing toward evening. The affected muscles fatigue if contraction is maintained or repeated.

       The most commonly affected muscles are the levator palpebrae, the extraocular muscles, the orbicularis, the proximal limb muscles, the muscles of facial expression, mastication, speech, and the neck extensors.

       The levator and extraocular muscles are initially affected, ptosis and strabismus are present in about 70% of cases. When weakness of these muscles is combined with weakness of the orbicularis, the combination is highly suggestive of Myasthenia Gravis.

       The diagnosis of myasthenia gravis is confirmed by dramatic relief of muscule weakness after I.V. injection of an anticholinesterase agents such as edrophonium chloride (Tensilon) which is a rapidly acting anticholinesterase and thus allows prolonged and repetitive action of acetylcholine at the the neuromuscular junction. Tensilon is chosen because of the rapid onset (30 sec) and short duration (about 5 min) of its effect.

        If the patient is Myathenic, the improvement of ptosis and ocular motility is dramatic and occurs within seconds after Tensilon injection( as shown in the attached video of this child ).

       It is preferred to administer the Tensilon test with the patient seated in the operating room, this gives an accurate evaluation of the improvement of ptosis.

       A 10-mg/mL solution of Tensilon is given intravenously. A second syringe containing 0.5 to 1.0 mg of atropine to counteract side effects should be readily available. Initially, a 1- to 2-mg test dose is given and the patient is observed for the development of hypotension, bradycardia, or arrhythmia.The injection is then continued 1 to 2 mg every 60 seconds until a positive response is obtained or the syringe is empty.