Pseudo-internuclear ophthalmoplegia with downshoot in myasthenia gravis

Internuclear ophthalmoplegia is characterized by an adduction deficit on lateral gaze with dissociated nystagmus of the abducting eye. It is seen with lesions of the medial longitudinal fasciculus. In myasthenia gravis, extraocular muscle weakness can cause the same oculomotor pattern, which has been referred to as pseudo-internuclear ophthalmoplegia. We report the additional finding of downshoot in the adducting eye in two patients with pseudo-internuclear ophthalmoplegia and positive Tensilon tests.