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| USMLE Step 1 Forum USMLE Step 1 Discussion Forum: Let's talk about anything related to USMLE Step 1 exam |
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#1
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56-year-old man with history of hypertension woke up one morning with persistent vertigo. When he walked, he swayed to the right with occasional falls. He complained of dysphagia. Examination showed loss of the gag reflex on the right and leftward deviation of the uvula, among other signs and symptoms.
T2-weighted axial image ![]() click image to enlarge The most commonly affected artery is: A) Posterior inferior cerebellar artery B) Anterior Spinal Artery C) Vertebral artery D) Superior cerebellar artery E) Posterior cerebral artery |
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#4
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Quote:
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| The above post was thanked by: | ||
bebix (06-18-2011)
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#8
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Quote:
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#9
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somebody else wants to try?
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#10
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correct answer MC artery => Vertebral artery
An infarct of the posterolateral medulla produces the lateral medullary or Wallenberg’s syndrome. The most commonly affected artery is intracranial vertebral artery occlusion (80%), followed by the posterior inferior cerebellar artery (PICA), superior middle and inferior medullary arteries. The constellation of signs and symptoms comprising Wallenberg’s syndrome can be deduced from the key structures within the posterolateral medulla, and are as follows: 1– Dyspahgia and hoarseness with ipsilateral loss of the gag reflex and ipsilateral vocal cord paralysis secondary to weakness of the pharyngeal and laryngeal muscles supplied by the nucleus ambiguus. 2– Loss of pain and temperature sensation from the ipsilateral face secondary to involvement of the spinal trigeminal nucleus and tract. 3– Loss of pain and temperature sensation from the contralateral body secondary to involvement of the lateral spinothalamic tract. 4– Ipsilateral cerebellar ataxia, including axial lateropulsion from involvement of the inferior cerebellar peduncle. 5– Vertigo, with associated nausea and vomiting, from involvement of the vestibular nuclei. 6– Ipsilateral Horner’s syndrome from involvement of the descending sympathetic fibers destined for the intermediolateral cell column. This is a pre ganglionic form of Horner’s. 7– Hiccuping, of uncertain etiology, but usually attributed to involvement of the respiratory center in the medullary reticular formation. 8– Abnormalities of saccades, referred to as ocular lateropulsion, are also characteristic of this syndrome, described as hypometric saccades away from the side of the lesion and hypermetric saccades towards the side of the lesion. This is probably secondary to damage of olivocerebellar fibers related to ocular movement traveling in the lateral medulla. Lateral medullary or Wallenberg’s syndrome: ![]() click image to enlarge ![]() click image to enlarge ![]() click image to enlarge |
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#11
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Tricky question!
Do you think it is more appropriate to ask "which of the following is the most likely site of occlusion" rather than "most commonly affected?" Even though the most common site of occlusion is indeed the Vertebral artery, the PICA is almost always "affected" because it is the branch that supplies the lateral medulla. Thoughts? Good question though, I had no idea that vertebral artery stenosis was the most common cause of wallenberg's! Keep em coming bebix, got my exam on Wednesday!
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#12
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I hope they don't give us both of the options of PICA or vertebral artery on the test because I would still be hesitant to choose vertebral artery!
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#13
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Quote:
Actually the vertebral artery is the MC artery affected (occlusion, dissection...) ![]() and remember...this syndrome is almost always due to infarction... a small number of cases are the result of hemorrhage or tumor. Last edited by bebix; 06-18-2011 at 06:59 AM. Reason: added info |
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#14
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btw, this question is from Clinical Neuroradiology
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#15
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So would there not be any collateral flow to the PICA if there is occlusion of the proximal vertebral artery?
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#16
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i guess with an acute lesion nop...
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| Figures- , MRI-Images , Nervous-System- , Neuroanatomy- , Pathology- , Step-1-Questions |
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