Cranial Nerve VII, The Facial Nerve
The muscular innervation of CN VII is tested by first observing the patient's face while at rest, specifically looking for nasolabial fold flattening or drooping of the corner of the mouth. The patient is then asked to raise eyebrows, wrinkle forehead, show teeth, puff out cheeks and close eyes tight (while examiner attempts to open eyes).
Any weakness or asymmetry may indicate a lesion in the facial nerve. In general, a peripheral lesion of CN VII will affect the upper and lower face while a central lesion will only affect the lower face.