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NBME 24 Answers

nbme24/Block 3/Question#28

A 22-year-old man is brought to the emergency ...

Area labeled ā€˜Eā€™ (Cerebellum, posterior lobe)

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submitted by seagull(433),

A- primary motor cortex = wrong side of body (deficit of UMN on left side body)

B - Thalamus = sensory information conduit - motor deficits unlikely to originate from here

C - Pons - CNs 8,7,6,5, likely result in "locked in syndrome" or complete loss of motor function on right side + facial features.

D. Vermis - central body coordination. Damage results in ataxia

Not complete but maybe helpful..

yotsubato  C - Pons - CNs 8,7,6,5, likely result in "locked in syndrome" or complete loss of motor function on LEFT side + RIGHT sided facial features. Decussation occurs in medulla +1  
kard  Sorry if im mistaken, Isnt A) Somatosensory? +1  
krewfoo99  Yes i think A should be somatosensory. Primary motor cortex would be present in the precentral gyrus +  

Dysmetria ( also, dysdiadokinesia and intention tremor) is lateral cerebellum. (E).

Ataxia is a problem with the central cerebellum (D) or at least thats the best I could come up with.

ronald-dumsfeld  I actually think D is pointing at the Flocculonodular lobe. See here: https://en.wikipedia.org/wiki/Flocculus_(cerebellar)#/media/File:Human_brain_midsagittal_view_description.JPG So a lesion at D would present with Nystagmus +1  
urachus  flocculonodular is medial (central). but yes it'll have nystagmus and truncal ataxia +  

Dysmetria = discoordination of planned, voluntary movements (my own words for the different findings and used specifically to help me remember location) controlled by the posterior lobe of the hemisphere which does planned voluntary movement. Also, the hemisphere is the periphery of the cerebellum, and it deals with planned, voluntary movements of the periphery (i.e. limbs). I got this from this image with memory tips: https://www.medicowesome.com/2013/04/cerebellum-mnemonics.html.

Other helpful links:

  1. Pretty detailed anatomy: http://www.fmritools.com/kdb/_Media/image002-3_med_hr.png

  2. Interactive site all about the cerebellum (https://nba.uth.tmc.edu/neuroscience/m/s3/chapter05.html), but the most helpful picture for me was this one (https://nba.uth.tmc.edu/neuroscience/m/s3/images/copyright_marked_images/5-3_NEW.jpg)

 +0  upvote downvote
submitted by m-ice(124),

Dysmetria is the lack of coordination of intended movements. Normally these movements are coordinated by the cerebellum. This is located specifically on the man's right side, not both sides, so only one lobe will be injured.