Gaze palsy and exotropia in internuclear ophthalmoplegia

Abstract Background and purpose Unilateral gaze palsy associated with internuclear ophthalmoplegia (INO), i.e., one-and-a-half syndrome, is well known. Exotropia can also be associated with INO, but it has been reported only rarely. We sought to determine the frequencies and courses of gaze palsy and exotropia in INO. Methods Patients hospitalized with acute-onset INO during the period January 2009 through December 2013 were identified from our clinical registry. Associated gaze palsy and exotropia were evaluated in the identified patients. Results Twenty-five patients with unilateral INO and 7 patients with bilateral INO were included in this study. Of the 25 patients with unilateral INO, 4 (16.0.0%) had ipsilateral gaze palsy (one-and-a-half syndrome), 8 (32.0%) had exotropia (non-paralytic pontine exotropia), and 6 (24.0%) had both ipsilateral gaze palsy and exotropia (paralytic pontine exotropia). Six (85.7%) of the 7 patients with bilateral INO had exotropia. The gaze palsy persisted more than 1 week in 40.0% of patients, whereas the exotropia disappeared within 1 week in 92.9% of patients when the INO was unilateral. Conclusion Exotropia is not uncommon in the acute stage of INO. However, it is often overlooked because of its short duration.