nine syndrome in acute pontine ischemic stroke: a rare case report and literature review

Background: nine syndrome is a rare condition with a manifestation of one and a half syndrome (oahs) with facial nerve damage and hemiparesis. we aimed to present the first published nine syndrome case from indonesia with a comprehensive physical examination, radiological diagnosis, and pathological pathway explanation. a case report analysis and literature review were conducted. case presentation: a 71-year-old male patient presented with the sudden onset of blurred vision and diplopia, with ‘one’ ipsilateral conjugate horizontal gaze palsy and ‘half’ ipsilateral internuclear ophthalmoplegia; a typical oahs condition. nine syndrome was diagnosed as ipsilateral lower motor neuron type facial nerve palsy and contralateral hemiparesis. it was radiologically confirmed by acute right pontine ischemic stroke, where the medial longitudinal fasciculus, abducens nucleus, and paramedian pontine reticular formation anatomically contribute to horizontal gaze. eye movement and hemiparesis improved significantly after ischemic stroke management. conclusion: nine syndrome is a neuro-ophthalmological manifestation that rarely occurs, and understanding the neuroanatomy and its possible causes may help clinicians in dealing with oahs and its various disorders.