Medial medullary syndrome, also known as Dejerine syndrome, is a vertebrobasilar arterial disease affecting the medial medulla that causes a classic clinical triad of contralateral hemiplegia / paresis, contralateral hemisensory loss, and ipsilateral tongue weakness. Symptoms are due to anterior spinal artery (ASA) and adjacent vertebral artery occlusion leading to infarct of the pyramidal tracts, medial lemniscus, and hypoglossal nucleus. This is very rare, representing less than 1% of brain stem stroke syndromes. Predisposing factors include typical vascular risk factors: age, hypertension, hyperlipidemia, diabetes, smoking, cardiac arrythmias, and hypercoagulable states.

Few patients will display the classic triad and many will demonstrate additional symptoms including quadriparesis / quadriplegia, flaccidity, dysarthria, dysphagia, diplopia, vertigo, headache, nystagmus, nausea, vomiting, and spasticity. Onset of symptoms is maximal within seconds to minutes and generally improves over the course of weeks to months. Prognosis depends on region of the medulla affected. In lesions limited to the upper third of the medulla, most patients will regain motor strength with minimal remaining effects. Lesions occurring in the lower two-thirds of the medulla are more commonly bilateral and may lead to respiratory compromise and more permanent sequalae.

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