A Rare Neuro-Ophthalmological Condition in a Patient with Lung Adenocarcinoma: The Eight-and-a-Half Syndrome, Case Report and Review of the Literature

The eight-and-a-half syndrome is a rare neuro-ophthalmological condition caused by a structural lesion in the dorsal portion of the pons, involving critical areas of the brainstem, i.e., medial longitudinal fasciculus (MLF), abducens nucleus, facial genu, and colliculus. It is characterized by internuclear ophthalmoplegia with horizontal gaze palsy and peripheral facial palsy. Although the syndrome is most frequently caused by vascular or demyelinating diseases, several different underlying causes might occur. Herein, we describe a case of the eight-and-a-half syndrome caused by a lung adenocarcinoma metastasis localized in the lower pontine tegmentum. Then, we review the current literature on the underlying causes of the eight-and-a-half syndrome.