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Pt has contralateral hemiplegia following an occlusion of paramedian branches of the basilar bifurcation on the right.
Which of the following would you expect to see in addition to the above stated signs?
1) paralysis of most movements of the left eye
2) deviation of the tongue
2) inability to voluntarily abduct the right eye
4) dilatation of the pupil on the right
5) complete paralysis of facial expression musculature on the left side
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Just a little guidance to answer this Q b/4 I post the correct answer.
This is a case of WEBER'S SYNDROM.
The Qs may come like this without the actual diagnosis mentioned.
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The paramedian branches of the basilar feed the medial pontine surface
you expect:
1. abducent nerve root compromise with ipsilateral rectus paralisis
2. there is no paralysis of facial expresion because the facial is intact, instead there is contrlaterl weakness of the lower face
3. the corcibo bulbar tracts that run posteriorely in the pons are affect so..contralateral hemiparesis is seen.
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Correct answer is (4)
Explanation:
Patients with Weber's Syndrom frequently exhibit involvement of the ipsilateral oculomotor tion of this nerve.
Interruption of this nerve on the right would eliminate parasympathetic outflow on that side, resulting in a dilated right pupil that does not react to light.
Movements of the left eye would not be affected.
Involvemet of the corticobulbar fibers coursing in the right crus cerebri might cause the protruded tongue to deviate to the left and cause paralysis of the facial expression musculature in the lower left portion of the face.
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But that is not the are of paramedian branches.
Indeed, the oclussion of the paramedian branches of the basilar artery is recognize as a MEDIALINFERIOR PONTINE SYNDROMe.
Weber Sd is due to occlusion of midran branches of the posterior cerebral artery...that is not what the question says (?)
Please, what is the source of the questions ?
The source or my answers is BRS neuroanathomy.
I wont to go ahead with this doubt.
thanks
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Hi elbamarita,
The source of this question is "USMLE Step 1 Appleton & Lange's Review, Second edition".
Those were the explanation and answer provided.
The following research are from other sources:
Weber's syndrom(ie superior alternating hemiplegia), is associatated with an oculomotor nerve palsy and contralateral hemiparesis or hemiplegia(UMN paralysis ie lower face and body).
It is caused by midbrain infarction, in other words, paramedian infarct of the midbrain as a result of occlusion of the paramedian branches of the basilar artery, leading to ipsilateral mydriasis & contralateral paresy.
I also have BRS for Neuroanatomy and I see what you mean. However, there too, like many other texts, it is clear that Weber's results from infarction of midbrain branches of posterior cerebral artery and the circle of Willis. Which is true. Note here that the emphasis is "medial midbrain"(meaning anatomical midbrain itself which houses the arteries) which is entirely different from the question here which specifies "paramedian branches of the midbrain artery" which are part of the vessels in the midbrain.
I hope that this clearifies things a bit more.
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thanks snowblack good q/nice explanation
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Thank you rebel71 for your kind words.
