Neroanatomy...1,2,3 - maryam2009

[ArchivalUser]

With a lesion of the corticospinal tract the greatest deficit will be noted in which one of the following areas?

A. The foot.
B. The hand.
C. The shoulder girdle muscles.
D. The pelvic girdle muscles.
E. The axial muscles.

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2.The upper motor neuron syndrome findings that are due to the loss of control and modulation of the indirect brainstem motor control centers by corticospinal collaterals include ALL of the following EXCEPT:

A. Increased tone – spasticity.
B. Hyperreflexia.
C. Clasp-knife phenomenon.
D. Babinski sign.

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3.A patient is unconscious and is noted to have extension of both the upper and lower extremities. This type of posture is most consistent with a lesion at which one of the following levels?

A. Cerebral hemispheres.
B. Midbrain.
C. Medulla.
D. Cervical spinal cord.

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[ArchivalUser]

1.B..The hand has a large cortical representation in the precentral gyrus and the anterior horn cells that innervate the hand receive almost exclusive input from the lateral corticospinal tract while more proximal and axial muscles also receive input from the indirect brainstem motor control centers so deficits are not as great in these muscle groups.
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2.
D..The Babinski sign is one of the few findings in the upper motor neuron syndrome that is due the loss of the direct corticospinal tract input on the lower motor neuron rather then the loss of control and modulation of the indirect brainstem motor control centers.
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3.
B..With a lesion of the midbrain both the upper and lower extremities will be in extension. This is decerebrate posture. The explanation for this is that with a lesion of the midbrain the influence of the rubospinal tracts has been eliminated so the indirect brainstem motor control centers that reinforce extensor tone in both the upper and lower extremities (the reticulospinal and vestibulospinal tracts) are unmodulated and unopposed.

[ArchivalUser]

Hey Maryam

Thanks for those question reviews... they are really useful

I thought that extension of upper and lower limbs indicated decerebrate ... meaning a lesion below the midbrain

In contrat lesions above mid brain present with decorticate signs flexion of arm and extension of legs

So B,C AND d can all be answeers for this question? what do u think?

[ArchivalUser]

Hi guys!
I studied this topic (decerebration n decortication), using this table.

Area---conscious state----findings

Cortical ----Letargy but arousal---- Cheyne-Stokes

Diencefalon----obtundation, Estupor------ decortication

midbrain----Coma-----decerebration, Kusmault

pons----coma----Extension upper, flexing lower,apnea

medulla----Coma-----Flaccid

Correction are most welcome...

Have a good day!

[ArchivalUser]

http://www.youtube.com/watch?feature=pla...ZUE2Dvf1Q4


A..A lesion in the cerebral hemispheres would result in decorticate posture which would be flexion of the upper extremities with extension of the lower extremities. The reason for this is that the rubospinal tracts are still functioning so upper extremities will be in flexion while the lower extremities will be in extension.

C..Medulla is wrong,...With a lesion in the medulla the patient is flaccid because all of the input from the indirect brainstem control centers has been interrupted.

D..With a lesion in the cervical spinal cord the patient is flaccid because all of the input from the indirect brainstem control centers has been interrupted. If the patient survives long enough then spasticity will eventually develop.


Thank you