Eight-and-a-Half Syndrome: A Case Report on a Rare Pontine Neuro-Ophthalmologic Presentation.

Eight-and-a-half syndrome is a distinctive neuro-ophthalmologic presentation resulting from a focal pontine lesion that simultaneously disrupts horizontal gaze pathways, internuclear connections, and facial nerve fibers. Clinically, it manifests as horizontal gaze palsy, internuclear ophthalmoplegia, and ipsilateral lower motor neuron facial weakness. We report a case of an elderly man with vascular risk factors who presented with the inability to perform conjugate horizontal gaze, adduction deficit of one eye with abducting nystagmus of the contralateral eye, and ipsilateral facial palsy, while vertical eye movements were preserved. Magnetic resonance imaging of the brain revealed an acute pontine infarction correlating with the neurological findings. This case highlights the importance of recognizing this characteristic constellation of signs for accurate anatomical localization and diagnosis.