CN VII Pathology
Petrous fractures can cause immediate facial nerve injury resulting in paralysis of facial expression. Peripheral CNVII injury may also be due to compression, tumor or aneurysm. Bell's Palsy is thought to be caused by idiopathic inflammation of the facial nerve within the facial canal. A peripheral CN VII lesion involves muscles of both the upper and lower face and can involve loss of taste from the anterior 2/3 of the tongue (via the chorda tympani).
A central CN VII palsy due to tumor or hemorrhage results in sparing of upper and frontal orbicularis occuli due to crossed innervation. Spared ability to raise eyebrows, wrinkle forehead helps differentiate a peripheral palsy from a central process.