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Old 07-20-2014
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Default Guys plz this question is driving me crazy ..Help

A 35-year-old man has a knife wound to the neck that completely destroys the left C6 dorsal root ganglion. Two months later , the axons , dendrites and nerve cell bodies of this damaged structure have completely degenerated , but there is no other damage. which of the following changes in the spinal cord will most likely be produced as a result of this injury?
A) Axonal loss in the contralateral Spinothalamic tract.
B) Nerve cell body loss in the ipsilateral dorsal horn.
C) Axonal loss in the ipsilateral dorsal columns.

And the Answer is C ,, why it can't be A or B ??
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Old 07-20-2014
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Quote:
Originally Posted by wa87el View Post
A 35-year-old man has a knife wound to the neck that completely destroys the left C6 dorsal root ganglion. Two months later , the axons , dendrites and nerve cell bodies of this damaged structure have completely degenerated , but there is no other damage. which of the following changes in the spinal cord will most likely be produced as a result of this injury?
A) Axonal loss in the contralateral Spinothalamic tract.
B) Nerve cell body loss in the ipsilateral dorsal horn.
C) Axonal loss in the ipsilateral dorsal columns.

And the Answer is C ,, why it can't be A or B ??
It says the root ganglion was destroyed, its cell body, dendrites and axon.

It can't be A, because, in that case the loss is always ipsilateral, because the damage is on the ganglion, no in the spinal cord. Remember the the second neuron axons from the spinothalamic tract cross to the other side in the spinal cord.

Neither B, because of same reason, the lesion is in the ganglion. Also remember the second neuron bodies of the dorsal column are in the medulla before the decussation (that's why is C), and spinothalamic's are in the dorsal horn.

Last edited by Mvp12; 07-20-2014 at 12:47 PM.
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Old 07-20-2014
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Thank you very much ,, I really appreciate your help ..Regards
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Thank you very much ,, I really appreciate your help ..Regards
You're welcome, just keep in mind where are located the cells bodies of each spinal tract.
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Old 07-20-2014
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I agree with the above.
Thanks
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In USMLE, “Any fool can know. The point is to understand.”
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You're welcome, just keep in mind where are located the cells bodies of each spinal tract.
Thank you very much .. I will hopefully soon
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Old 07-21-2014
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for dorsal column:
the first order neuron is from DRG to medulla
2nd order neuron decussates in medulla
so lesion to cell body of DRG will cause loss of axons of the entire ipsilat dorsal column

remember,in spino thal tract,
1st order DRG to dorsal horn
2nd order is dorsal horn-crosses ant comissure-c/l spinothal tract
so if the injury is at the dorsal root,and if it damages dorsal root cell body,then the axon of the spinothal tract will degenerate (Contralateral)
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Old 07-26-2014
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Quote:
Originally Posted by hypatia View Post
for dorsal column:
the first order neuron is from DRG to medulla
2nd order neuron decussates in medulla
so lesion to cell body of DRG will cause loss of axons of the entire ipsilat dorsal column

remember,in spino thal tract,
1st order DRG to dorsal horn
2nd order is dorsal horn-crosses ant comissure-c/l spinothal tract
so if the injury is at the dorsal root,and if it damages dorsal root cell body,then the axon of the spinothal tract will degenerate (Contralateral)
Thank you very much
I got the point with your help
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