Rare occurrence of eight-and-a-half syndrome as a clinically isolated syndrome.

Eight-and-a-half syndrome is a rare condition that is described as a combination of one-and-a-half syndrome and an ipsilateral facial nucleus lesion. We present a clinical case of occurrence of eight-and-a-half syndrome that was caused by a demyelinating lesion in the dorsal pontine tegmentum. A 44-year-old man presented to the hospital with a subacute onset of horizontal diplopia and left-sided facial weakness. MRI revealed a T2 hyperintense lesion in his dorsal pons, which was consistent with a demyelinating pathology. Treatment with intravenous steroids showed significant improvement in his symptoms. In our case, it occurred due to a suspected demyelinating lesion that was this patient's first and only demyelinating event, leaving him with a diagnosis of clinically isolated syndrome. His responsiveness to steroids represents the first case report of an adult patient presenting with an eight-and-a-half syndrome secondary to a suspected demyelinating pathology.