Loss of pain and temperature sensation on one side of the face, and the opposite side of the body. This can be produced by lateral lesions in the caudal pons or medulla which damage EITHER the descending (spinal) tract of V or the caudal part of the spinal nucleus of V AND the spinothalamic tract. By contrast, single lesions in the rostral pons or midbrain usually produce contralateral loss of pain and temperature in both face and body, since the part of the trigeminal system present at these rostral levels (second-order trigeminothalamic fibers) is mostly crossed.