Infarction of the dorsolateral aspect of medulla oblongata in the brain stem. it is caused by occlusion of the vertebral artery and/or the posterior inferior cerebellar artery. clinical manifestations vary with the size of infarction, but may include loss of pain and temperature sensation in the ipsilateral face and contralateral body below the chin; ipsilateral horner syndrome; ipsilateral ataxia; dysarthria; vertigo; nausea, hiccup; dysphagia; and vocal cord paralysis. (from adams et al., principles of neurology, 6th ed, p801)