Figure 11 An example of the one-and-a-half syndrome in one of our patients with multiple sclerosis

The patient was unable to elicit saccades to the right (i.e., a right gaze palsy), and had evidence of a right internuclear ophthalmoparesis (INO) upon attempted gaze to the left. In this photograph, the patient is looking straight ahead. We can observe an exotropia, the so-called paralytic pontine exotropia with the left eye in exo (the only remaining movement possible). In this circumstance, there is an attempted leftward preference. However, only left eye abduction is possible given the right INO (with slowing and significant ocular limitation). Below is the T2-weighted axial MRI showing the responsible lesion involving the right pontine tegmentum (arrow).