Lateral medullary syndrome

Last revised by Liz Silverstone on 27 Jan 2024

Lateral medullary syndrome, also known as Wallenberg syndrome, is a clinical syndrome caused by acute ischemia or infarction of the lateral medulla oblongata due to occlusion of the intracranial portion of the vertebral artery, PICA or its branches 1-3

20% of ischemic strokes occur in the posterior circulation 5. Lateral medullary syndrome is the most prevalent posterior ischemic stroke syndrome 5.

Hypertension is the commonest risk factor followed by smoking and diabetes mellitus 5.

This syndrome is characterized by:

  • vestibulocerebellar symptoms: ipsilateral hemiataxia, vertigo, falling towards the side of lesion, multidirectional nystagmus (inferior cerebellar peduncle and vestibular nucleus1-3

  • autonomic dysfunction: ipsilateral Horner syndromehiccups 1-3

  • sensory symptoms: loss of pain and temperature over the ipsilateral face (this may be variable 8) and contralateral side of body 1-3

  • ipsilateral bulbar muscle weakness: hoarseness, dysphonia, dysphagia, and dysarthria, decreased gag reflex (nucleus ambiguus1-3

Affected structures can include:

  • inferior cerebellar peduncle

  • dorsolateral medulla

  • descending spinal tract

  • nucleus of the trigeminal nerve

  • vagus nucleus and nerve

  • glossopharyngeal nucleus and nerve

  • descending sympathetic tract fibers

Lateral medullary syndrome is most commonly caused by vertebral artery disease. Underlying pathology includes:

  • atherothrombotic occlusion of the vertebral artery, the posterior inferior cerebellar artery or the medullary arteries

  • cerebral embolism

  • vertebral artery dissection, the commonest cause in young patients

  • hypoplastic vertebral artery 7

MRI with DWI is the best diagnostic test to confirm the infarct in the lateral medulla 6. The infarcted area has high DWI signal and is low signal on ADC 6.

The syndrome was first described by Adolf Wallenberg (1862-1949), a German physician, in 1895 4.

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