neurophys question on tract lesion - USMLE Forums
USMLE Forums Logo
USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
Home
USMLE Articles
USMLE News
USMLE Polls
USMLE Books
USMLE Apps
Go Back   USMLE Forums > USMLE Step 1 Forum

USMLE Step 1 Forum USMLE Step 1 Discussion Forum: Let's talk about anything related to USMLE Step 1 exam


Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 10-06-2010
USMLE Forums Newbie
 
Steps History: ---
Posts: 2
Threads: 1
Thanked 0 Times in 0 Posts
Reputation: 10
Heart neurophys question on tract lesion

Can someone help me out with this question below...

A 64-year-old female patient is referred to a neurologist because her sister and brother both suffered recent strokes. She is diagnosed with an antiphospholipid antibody syndrome, a condition that causes hypercoagulation, and placed on warfarin. Despite the anticoagulation therapy she develops a thrombotic cerebral infarct, which leads to spasticity of her left wrist, elbow, and knee. The lesion most likely affected which of the following?

a. The corticospinal fibers
b. The vestibulospinal fibers
c. The Ia afferent fibers
d. The corticoreticular fibers
e. The reticulospinal fibers


Ok the answer is corticoreticular fibers but why not corticospinal fibers?? I thought UMN lesion's are the cause of spasticity due to damage in the corticospinal tracts?? ughhh... this neuro stuff!!! Please helpppp!
Reply With Quote Quick reply to this message



  #2  
Old 10-07-2010
Ex-USMLE Forums Staff
 
Steps History: 1+CK+CS+3
Posts: 753
Threads: 106
Thanked 2,166 Times in 464 Posts
Reputation: 2214
Unhappy Could not get it

What was the explanation given with the answer?
I can't get this question either.
Cortico-reticular tract is actually a part of the corticospinal tract as a whole as far as I know.
Involvement of the proximal muscles only may suggest cortico-reticular rather than corticospinal but the question is also mentioning wrist involvement which is not proximal.

Don't worry, you always get questions that are poorly constructed. In the real exam there won't be such questions, hopefully
Reply With Quote Quick reply to this message
  #3  
Old 10-07-2010
USMLE Forums Newbie
 
Steps History: ---
Posts: 2
Threads: 1
Thanked 0 Times in 0 Posts
Reputation: 10
Default

Hey Lee, yeah, there was an answer given, I actually got this from the Pre-Test Physiology book but I still dont get it even after reading the answer lol Here's what it said:


Spasticity results from overactivity of the a motoneurons innervating the skeletal musculature. Under normal circumstances, these alpha motoneurons are tonically stimulated by reticulospinal and vestibulospinal fibers originating in the brainstem. These brainstem fibers are normally inhibited by fibers originating in the cortex. Cutting the cortical fibers releases the brainstem fibers from inhibition and results in spasticity. Cutting the fibers from the reticular formation, vestibular nuclei, or the Ia afferents will reduce the spasticity.
Reply With Quote Quick reply to this message
  #4  
Old 10-07-2010
Ex-USMLE Forums Staff
 
Steps History: 1+CK+CS+3
Posts: 753
Threads: 106
Thanked 2,166 Times in 464 Posts
Reputation: 2214
Default

Quote:
Originally Posted by Clawhand View Post
Hey Lee, yeah, there was an answer given, I actually got this from the Pre-Test Physiology book but I still dont get it even after reading the answer lol Here's what it said:


Spasticity results from overactivity of the a motoneurons innervating the skeletal musculature. Under normal circumstances, these alpha motoneurons are tonically stimulated by reticulospinal and vestibulospinal fibers originating in the brainstem. These brainstem fibers are normally inhibited by fibers originating in the cortex. Cutting the cortical fibers releases the brainstem fibers from inhibition and results in spasticity. Cutting the fibers from the reticular formation, vestibular nuclei, or the Ia afferents will reduce the spasticity.
Could not understand either!
Let's see if someone else can help us here...
Reply With Quote Quick reply to this message
  #5  
Old 10-07-2010
USMLE Forums Guru
 
Steps History: ---
Posts: 487
Threads: 69
Thanked 294 Times in 133 Posts
Reputation: 314
Default

Corticoreticular fibers are one of the major output pathways from the motor cortex to the brainstem. They project widely and diffusely within the pontomedullary reticular formation. Such a diffuse projection pattern seems well suited to combining and integrating the function of the various types of reticulospinal neurons, which are widely scattered throughout the pontomedullary reticular formation. The corticoreticular-reticulospinal-spinal interneuronal connections appear to operate as a cohesive, yet flexible, control system for the elaboration of a wide variety of movements, including those that combine goal-directed locomotion with other motor actions.

hmmmm.....well every one will make mistake of selecting corticospinal tract...so do not worry about this kind of Qs....



but we can differntiate.....by "spasticity of wrist, elbow, and knee"
they hv not mentioned spasticity of whole limb.....
__________________
258(1)/237(1)/CS pass(1)/YOG 2011/221(1)/6 months USCE/ 3 months observership/4 US LOR /Need visa
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message



Reply

Tags
Neuroanatomy-, Step-1-Questions

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the USMLE Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Medical School
Choose "---" if you don't want to tell. AMG for US & Canadian medical schools. IMG for all other medical schools.
USMLE Steps History
What steps finished! Example: 1+CK+CS+3 = Passed Step 1, Step 2 CK, Step 2 CS, and Step 3.

Choose "---" if you don't want to tell.

Favorite USMLE Books
What USMLE books you really think are useful. Leave blank if you don't want to tell.
Location
Where you live. Leave blank if you don't want to tell.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Cortical lesion? Sujay88 USMLE Step 1 Forum 6 02-13-2015 05:54 PM
Brain Stem Lesion lee-usmle USMLE Step 1 Forum 9 06-10-2014 05:57 PM
Upper & Lower Respiratory Tract Infection? achistikbenny USMLE Step 1 Forum 7 10-17-2011 09:41 PM
lesion of the corticospinal tract sohni USMLE Step 1 Forum 9 03-31-2011 12:24 AM
an accidentally discovered lesion DrSeddik USMLE Step 1 Forum 8 11-28-2009 04:39 PM

RSS Feed
Find Us on Facebook
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.

USMLE® & other trade marks belong to their respective owners, read full disclaimer
USMLE Forums created under Creative Commons 3.0 License. (2009-2014)