Therefore, a lesion that is caudal to the sensory decussation where the remaining three-fifths modalities decussate (at the superior medulla) will result in contralateral (opposite sided) pain and temperature loss (as this has already crossed over at the anterior white commissure), whereas loss of crude touch, pressure, and proprioception will be ipsilateral (same sided) as these have not yet crossed over.
Consequently, a lesion located posterior to the sensory decussation where the remaining three-fifths of the modalities cross over (at the superior medulla) will result in opposite-sided pain and temperature loss (as these have already crossed over at the anterior white commissure), whereas loss of crude touch, pressure, and proprioception will be on the same side as these have not yet crossed over.