Electromyogram (EMG) studies were carried out in seven patients with thyrotoxic ophthalmoplegia and one post-thyrotoxic case without clinical evidence of extraocular paresis. Fifteen extraocular muscles were examined, 12 were paretic and 3 clinically healthy. Of the 12 paretic muscles, one exhibited a myasthenic reaction while the other 11 were myopathic. The three clinically normal muscles were also myopathic from the EMG point of view.
Magora A, Chaco J, Zauberman H. An Electromyographic Investigation of Ophthalmoplegia in Thyrotoxicosis. Arch Ophthalmol. 1968;79(2):170-173. doi:10.1001/archopht.1968.03850040172012