The head and face are innervated by twelve separate “cranial” nerves. Each of these nerves has a different function. For example, the first cranial nerve (CN1) controls smell, while the eighth nerve (CN8) controls hearing. The main nerve we are concerned with is the second nerve (CN2) which is the optic nerve and transmits visual signals to the brain. The other nerves we watch are the ones that control eye movement … this is the third (CN3), fourth (CN4) and sixth (CN6) nerves. If these “motility nerves” become damaged we call this a “palsy.” Most cranial nerve palsies occur because of vasculopathic problems like diabetes or hypertension where the nerve doesn’t get enough oxygen and shuts down. This is usually temporary and improves over six months. Other causes are more concerning, such as a tumor or aneurysm pushing on the nerve. See the entries on third nerve palsy, 4th nerve palsy, and sixth nerve palsy for more information.