What is the definition of the lateral medullary syndrome (LMS)?
The lateral medullary syndrome (LMS) or Wallenberg syndrome is a brainstem infarction, with damage to the lateral segment of the medulla posterior to the inferior olivary nucleus.
What nucleus and areas of the brainstem are usually damaged in Wallenberg syndrome?
Wallenberg syndrome is a brainstem infarction, with damage to the lateral segment of the medulla, and involvement of vestibular nuclei, restiform body, trigeminal tracts and nuclei, and spinothalamic tract at the medulla.
Which arteries are most likely occluded to cause this clinical problem in LMS?
The most likely occluded arteries in LMS are the vertebral artery, the posterior inferior cerebellar artery (PICA), and the medullary arteries.
Which symptoms and signs characterize of Wallenberg syndrome?
The clinical features of Wallenberg syndrome are well-known, and the diagnosis is possible if there are at least three of the following five most frequent signs: ipsilateral Horner`s sign, ataxia, ipsilateral facial hypalgesia, hypalgesia in contralateral dimidium, and palsy of cranial nerve IX or X. Patients may also present vertigo, ataxia, nausea, and vomiting.
What are the typical MR imaging findings of this disease?
The MRI with diffusion-weighted imaging is the best diagnostic test to confirm the infarct in the lateral medulla. The infarcted area appears as hyperintense on B1000 and low signal on the ADC map.
Slightly hypointense focal area on axial T1-weighted images, and hyperintense lesion on T2-weighted and FLAIR imaging involving the posterolateral aspect of the right medulla, suggestive of an infarct, without evidence of hemorrhage. DWI (B1000) shows increased signal intensity with corresponding low ADC at the right lateral medulla, consistent with acute/subacute infarction.
Contrast-enhanced 3-D MRI angiography sequence shows that a long segment of the right vertebral artery is not visualized, probably caused by dissection.
Three-dimensional time-of-flight (TOF) MR angiography sequence demonstrates the absence of the right vertebral artery.
There is a discrete focal area with diffusion-restricted in the left medial occipitotemporal gyrus, probably representing infarction due to embolism from the right vertebral artery dissection.