Bilateral pseudo-internuclear ophthalmoplegia in a patient with myasthenia gravis

Abstract

PurposeTo report a case of myasthenia gravis presenting with a false localizing sign, a bilateral pseudo internuclear ophthalmoplegia.ObservationsA 61 year-old male presented with a five-week history of painless binocular oblique diplopia that was associated with fatigue, vocal hoarseness and bilateral ptosis, the latter two of which worsened through the course of the day. Exam was remarkable for an apparent bilateral internuclear ophthalmoplegia (INO). MRI of the brain with and without contrast and MRA of the head and neck were within normal limits. Lab work was positive for anti-AChR binding, blocking, and modulating antibodies, as well as anti-striated muscle and anti-titin antibodies. The patient was initiated on therapy for myasthenia gravis.Conclusion and importanceAlthough myasthenia gravis often presents with ptosis or diplopia, rarely patients may develop pseudo-INO secondary to extraocular muscle weakness. True INO occurs with damage to the medial longitudinal fasciculus, a myelinated tract of fibers that controls yoked horizontal eye movements. Clinicians should be suspicious of the false localizing sign of a pseudo-INO associated with myasthenia gravis when more common causes of INO have been excluded.

Ocular Myasthenia Gravis: A Current Overview

“…25,26 Pseudo-internuclear ophthalmoplegia (unilateral or bilateral), pseudo-one-and-a-half syndrome, complete external ophthalmoplegia, divergence and convergence paresis, and double elevator palsy have all been described in OMG. 27,28 The clinical diagnosis can be challenging and often delayed, particularly in the absence of ptosis. Since OMG can mimic various ocular motility disorders, some of which may be life-threatening, MRI brain imaging may be necessary in case of diagnostic uncertainty.…”