[A case of infarction in the pontine tegmentum involving the bilateral MLF and unilateral paramedian pontine reticular formation]

A 61-year-old man with lesions of the bilateral medial longitudinal fasciculus (MLF) and left paramedian pontine reticular formation (PPRF) caused by an infarction in the pontine tegmentum was reported. On admission, the ocular position of the left eye on forward gaze was fixed at the midline, while the right eye was abducted, and skew deviation was observed. On leftward gaze, neither eye could pass the midline, and on rightward gaze the right eye was abducted with monocular nystagmus, indicating paralytic pontine exotropia. On the fifth day, the bilateral eyes were abducted on forward gaze. On leftward gaze, the left eye was abducted slightly with monocular nystagmus. On rightward gaze, the right eye was abducted with monocular nystagmus. This issue was considered to be walleyed bilateral internuclear ophthalmoplegia (WEBINO). On the 37th day, right MLF syndrome was noted. About 2.5 months later, the disturbances of ocular movement disappeared. T2-weighted MRI showed high signal intensity lesions in the bilateral paramedian portion of the midpontine tegmentum. It suggests that WEBINO is caused by a lesion in the pons, and that paralytic pontine exotropia, one and a half syndrome and WEBINO are considered to be analogous to one another. The associated abnormality of vergence eye movements suggests that these are also generated by the PPRF in the pons.