[Myasthenic internuclear pseudo-ophthalmoplegia].

Two cases of myasthenic pseudointernuclear ophthalmoplegia are reported. The diagnosis of this rare peripheral oculomotor syndrome is established on the variability of the clinical signs, their improvement by pharmacological testing, the combined impairment of convergence, the usual association of ptosis, and in some cases the presence of specific electromyographic signs. The nystagmus of the abducting eye could result from a selective damage to the tonic muscle fibres mediating fixation, the phasic fibres (performing saccades) being spared.