Presentation
Sudden-onset right occipital pulsatile headache, dizziness, unsteady gait with falling to the right, sweating, hoarseness, difficulty swallowing, and uncomfortable hiccups.
Patient Data
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.
Case Discussion
Lateral medullary syndrome (LMS) or Wallenberg syndrome is a brainstem infarction that presents as a clinical syndrome with typical neurological symptoms and signs because of its location 1. It is usually secondary to the vertebral artery and posterior inferior cerebellar artery occlusion due to atherothrombosis or embolism, and also due to a spontaneous dissection of the vertebral arteries 1-3.
The most usual pattern of sensory abnormality in this disease is a cross pattern, with loss of temperature and pain sensation in the ipsilateral face (trigeminal tracts and nuclei) and the contralateral trunk and limbs (spinothalamic tracts) 4. This disease occurs as a result of damage to the lateral segment of the medulla posterior to the inferior olivary nucleus 2, with the involvement of vestibular nuclei, restiform body, trigeminal tracts and nuclei, and spinothalamic tract at the medulla.
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, ipsilateral ataxia, ipsilateral facial hypoalgesia, contralateral body hypoalgesia, and palsy of ipsilateral cranial nerve IX or X 1,5. The manifestation is broad, and patients may present vertigo, ataxia, nausea, emesis, numbness, facial pain, visual disturbance, hoarseness, and hiccups 1,2,5. Occipital headache is one of the most important clinical symptoms of Wallenberg syndrome due to vertebral artery dissection 6.
Magnetic resonance imaging (MRI) with diffusion-weighted imaging is the best diagnostic test to confirm the infarct in the lateral medulla 1. The infarcted area is hyperintense on B1000 and low signal on the ADC map.
The presumed pathogenetic mechanism of the Wallenberg syndrome in this patient was right vertebral artery dissection, with an infarcted area in the right lateral medulla and a possible contralateral embolism from this dissection, with another infarcted area in the left medial occipitotemporal gyrus.
Case courtesy
Sterfferson Morais, MD - PGY-3, Radiology Resident, Department of Radiology
Antonio Rodrigues de Aguiar Neto, MD - Radiologist, Department of Radiology
Hospital da Restauração – Recife, PE – Brazil
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