Double vision in a patient with thyroid disease: what's the big deal?

A 70-year-old woman with a 46-year history of Graves disease had significant thyroid related orbitopathy (TRO) requiring previous bilateral orbital decompressions and one previous strabismus procedure for an exotropia of 60 PD. At the initial neuro-ophthalmology assessment, she had an exotropia of 20 PD and was scheduled for further surgery, but at the time of a second assessment a few weeks later, her strabismus had markedly changed. Accordingly, the patient underwent a neostigmine bromide test that demonstrated evidence of co-existing myasthenia gravis.