An injury to the lateral spinothalamic tract in the spinal cord would most likely result in:

The lateral spinothalamic tract is responsible for transmitting pain and temperature sensations from the body to the brain. The fibers of this tract decussate (cross over) in the spinal cord shortly after entering. This means that an injury to the lateral spinothalamic tract on one side of the spinal cord will result in sensory deficits on the opposite side of the body.

Let's evaluate the options:

• A. paralysis of extremities on the opposite side of the body: Paralysis is a motor deficit, typically caused by damage to motor pathways like the corticospinal tract, not the lateral spinothalamic tract.
• B. pain deficits on the opposite side of the body: This is consistent with the function of the lateral spinothalamic tract (pain sensation) and its decussation in the spinal cord.
• C. proprioceptive deficits on the same side of the body: Proprioception is carried by the dorsal column-medial lemniscus pathway, which decussates in the brainstem, not the spinal cord. An injury to this pathway in the spinal cord would cause deficits on the same side. This is not related to the lateral spinothalamic tract.
• D. temperature deficits on the same side of the body: While temperature sensation is carried by the lateral spinothalamic tract, the deficits would be on the opposite side of the body due to the decussation of its fibers in the spinal cord.

Therefore, an injury to the lateral spinothalamic tract would cause pain and temperature deficits on the opposite side of the body. Option B correctly identifies pain deficits on the opposite side.

The correct answer is B.