In general, due to the cross-innervation of nerve fibres, a LMN lesion results in paralysis or weakness of both upper and lower parts of the face, whereas an upper motor neuron (UMN) lesion usually spares the upper part of the face (i.e patient can wrinkle forehead on that side). Note however that this is not always absolute.
njury to the central cord commonly occurs after a fall or motor vehicle collision where there is hyperextension at the neck. The syndrome presents with bilateral motor paresis. Sensory impairment may be present as well. The upper extremities are affected more often and to a greater degree than the lower extremities. Additionally, distal muscle groups are more affected than proximal ones. Bladder dysfunction and burning dysethesias may also be present.