Re: What causes pain/temperature loss in Wallenberg's Syndrome?

Wallenberg’s Syndrome is also called posterior inferior cerebellar artery 
syndrome and lateral medullary syndrome (due to involvement of structures of 
the lateral medulla).  It is usually due to a blockage of the vertebral 
artery less often due to blockage of one or more branches of the vertebral 
artery.  The loss of pain and temperature sensation of the face is 
ipsilateral due to involvement of the sensory trigeminal nucleus or the 
descending tract.  The loss of pain and temperature sensation of the trunk 
and limbs is contralateral due to damage to the spinothalamic tract.  There 
is almost certainly a topographic map for pain and temperature in the 
medulla since these maps are well established for the thalamus and sensory 
cortex.  However, the relatively small size of medullary nuclei make it 
unlikely that you would lose only a portion of one nuceli due to a ‘small’ 
infarct.