Monoplegia refers to the paralysis of a single limb, hemiplegia refers to the paralysis of the same limb, paraplegia refers to the paralysis of both lower limbs, and quadriplegia refers to the paralysis of both upper and lower limbs. In monoplegia, the injury site is close to the cerebral cortex; in hemiplegia, the injury site is usually located where the motor nerve fibers are located, such as the internal capsule and brainstem; and in paraplegia, the thoracic or lumbar medulla is mainly damaged. High paraplegia, or tetraplegia, damages the spinal cord above the cervical expansion or the brainstem bilaterally. If the patient has a more concentrated motor fiber injury, the paralysis will be more severe. If the lesion is semi-oval-centric, it will produce heterogeneous paresis, which manifests as unequal degrees of paralysis in the upper and lower extremities. MRI is useful to detect the location of the lesion damage.