Medial longitudinal fasciculus syndrome associated with a subdural hygroma and an arachnoid cyst in the middle cranial fossa.

A 60-year-old man complaining of diplopia and vertigo showed bilateral medial longitudinal fasciculus (MLF) syndrome. The CT scan revealed a space-occupying lesion with watery fluid in the left cranial fossa, which was divided into two parts by a thin septum. Surgical trepanation was performed followed by 4 weeks of prednisolone therapy. He was completely cured 5 months later. The plausible causes of MLF syndrome relevant to preexisting space-occupying lesions are discussed.