Chapter contents Branchial motor Visceral motor Special sensory General sensory Peripheral lesions

Cranial Nerve VII - Facial Nerve Page 13 of 28 Clinical Correlation - Upper Motor Neuron (UMN) Lesion Results from damage to neuronal cell bodies in the cortex or their axons that project via the corticobulbar tract through the posterior limb of the internal capsule to the motor nucleus of CN VII. With an UMN lesion, voluntary control of only the lower muscles of facial expression on the side contralateral to the lesion will be lost. Voluntary control of muscles of the forehead will be spared due to the bilateral innervation of the portion of the motor nucleus of CN VII that innervates the upper muscles of facial expression. UMN lesions are usually the result of a stroke.

		Figure 7-11. Figure 7-11. Clinical correlation - Upper Motor Neuron (UMN) Lesion. After Wilson-Pauwels, et al., 1988. Characteristics of an UMN lesion of the facial nerve include: Facial asymmetry Atrophy of muscles of lower portion of the face on affected side* No eyebrow droop* Intact folds on forehead* Intact conjunctival reflex (orbicularis oculi innervation is intact) Smoothing of nasolabial folds on affected side Lips cannot be held tightly together or pursed Difficulty keeping food in mouth while chewing on affected side *Distinguishes UMN lesions from LMN lesions.

Last revised: March 22, 1998