unilateral lesion
a lesion on one side or lobe of an organ or part. For example, a unilateral cerebral lesion involves one cerebral hemisphere, left or right, with effects that may vary according to the dominance of the hemisphere and the function affected. The motor and sensory effects of the lesion are generally on the contralateral side—that is, on the side opposite to that of the lesion—unless the lesion occurs in the cerebellum.