Question: If a patient has a lesion on one side of the spinal cord, which side of the body will his/her pain and temperature sensation be lost? Ipsilateral or contralateral?

See below.

• Notice in the spinal cord how the leg fibers in the posterior columns (gracile fasciculus) are medial to the arms but in the ALS they are lateral
• It is often taught that a central spinal cord lesion (eg tumor) can result in “sacral sparing.” Why?
  
  See below.