Bilateral internuclear ophthalmoplegia in a 53-year-old man with diplopia on lateral gazes. A, Horizontal gaze in either direction results in full abduction of the ipsilateral eye but virtually no adduction of the contralateral eye. Alignment in primary gaze (center panel) is nearly orthotropic. B, Axial FLAIR MRI brain scan showing edema (bright signal indicated by arrows) in the area of the medial longitudinal fasciculus bilaterally at the level of the upper midbrain (left) and pons (right).