Question

why does a small central cord lesion only affect pain and temperature sensation?
because axons of the spinothalamic tract decussate at the ventral commissure
because the anterior horn cells are damaged
because the corticospinal tract is compressed centrally
because the posterior columns are primarily affected

Explanation:

Pain and temperature sensations are transmitted via the spinothalamic tract. The axons of this tract cross over (decussate) at the ventral commissure, which is located in the central region of the spinal cord. A small central cord lesion targets this area, disrupting the crossing spinothalamic axons. In contrast, the anterior horn cells control motor function, the corticospinal tract controls voluntary motor movement, and the posterior columns carry fine touch and proprioception—none of these are involved in pain/temperature sensation or are the primary target of a small central lesion.

Answer:

A. Because axons of the spinothalamic tract decussate at the ventral commissure