This is a very nitpicky question. As I see it, the 3 main concepts tested are:

• This patient has trigeminal neuralgia (sharp, brief, episodic pain in the face), which is caused by a lesion to primary sensory fibers that carry pain sensation from the face.
• Multiple sclerosis, which the patient has, is a demyelinating disease (i.e., it affects white matter).
• The myelinated axons carrying pain sensation from the ipsilateral face enter the brainstem at the level of the pons and then descend (become the spinal tract of the trigeminal). These white matter fibers pass through the pons to synapse on the spinal nucleus of the trigeminal, which is in the medulla (nucleus = gray matter). (picture here). Therefore, a lesion in the white matter (i.e., plaque) in the pons could cause trigeminal neuralgia, and this phenomenon has been observed.

Above the level of the brainstem (thalamus & cerebral cortex), you have second order sensory neurons. Lesions in this part of the circuit are not generally in trigeminal neuralgia. I suppose they also want us to assume that once the spinal tract of the trigeminal enters the medulla, it's not myelinated anymore. I don't think this is completely true, but given the logic described above, pons would still be the better answer.

As people have pointed out, the primary sensory fibers carrying light touch sensation from the face synapse on the chief sensory nucleus in the pons immediately after they enter the pons. This question is not asking about those fibers though.

I got the question wrong too..

eTh minocnme I eikl ofr bgremnrieme teh oncloitas of hte lnaaicr nveers si eth 42,"4,,2 eur"l

evbAo etir=msbna CN I + iIndbr=a MiI CN ,III P= VoIsn CN V, IV, VI,I MuVIl lIaI=ed CN X,I ,X ,IX IIX

rpPilneic eonysrS lcesNuu fo het elaiTgnmir is deoltca in the s,oPn sa si het roMot mneTgriila ucNeuls of eht .nops hisT repannsiotet si bbpralyo igeland erom hitw het riPpilcen Sseoynr uluecsN.

The npos sah enersv -58, os het rlteaiimgn dlwuo eb tdafecfe here

I od atresndnud ttha teh piacpnlir enusulc fo hte erniimtgla reven is cadotel ta hte pon.s uBt csine tish enpttai si hginav rmgileiatn reluiagna 'tlowdun uoy be nurtsiipdg teh htpaywa envldvoi ni ainp and aeem,utrprte ihhcw in tshi scae wldou be hte anlspi nesuluc aodle(ct ni eht l)admule?

siee,dBs I ufnod htsi at an aelirtc

A enetrc oshhesptiy ttestaibru teh pina of griiltmean alenragiu to a ncleart hiscmnmea ionivvngl teh pras orslia of hte saplni ngiliaetmr [n]us.cleu5

9ownbo5/hit7cnpol..wgb:3kmv/tKw9//2nNB/.hss.i

Per boards and beyond, in the lateral pons is there is the spinal V nucleus which carries contralateral pain and temperature. Knowing that + CN V arises it in the pons, I went with pons. The only other option I had left not crossed out was cerebral hemisphere but that seemed to broad.

etersh na tcsooanisai mdae ni 0127 whti airmnlietg lnuareiga and SM - ihhwc is hatw i hknti hist pt sha. yke hngit to eotn si that eiwlh all ortom adn yrsoesn eifsrb of NC 5 rteen at hte elvle of het onps oehe(wvr emos lsao do etenr ta the vlele of delulma dna veen teh cs vai het nlpais rttac fo 5 to aesnspy hwit hte lngo nroseys clueusn fo )5 se rhe hte knil of limeigrant laeairugn dna S :Mo.ii6.wewn7/Mt/P5wlshrc.Ccpth/cva3bn4ng/ml9.i//psmt4:

I wsa nktngiih oalng hte lisne fo laiafc etaossinn whchi si mdadeeti yb het liigemarnt rveen dan eth afct htat the legnritmia veren is dealcto ni eht sop.n