Radiologic-clinical correlation. One-and-a-half syndrome associated with cheirooral syndrome.

Lesions that involve the paramedian pontine reticular formation (PPRF) or the sixthnerve nucleus on one side of the brain stem and also interrupt internuclear fibers of the ipsilateral medial longitudinal fasciculus produce an ipsilateral horizontal gaze palsy combined with an internuclear ophthalmoplegia, so that the only preserved horizontal eye movement is abduction of the contralateral eye (1). This syndrome consists of a complete horizontal gaze palsy when the patient looks toward the side of the lesion, combined with half gaze palsy when the patient looks in the opposite direction, and has been termed the “one-and-a-half syndrome” (2–5).