Bell's Palsy Symptoms
Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: Charles Patrick Davis, MD, PhD
Bell's palsy is a condition that affects the facial nerve, and therefore the function of the muscles, on one side of the face. The facial nerve is one of the 12 cranial nerves and is given the designation of the 7th cranial nerve (CN VII). There is a facial nerve on each side of the face. This nerve can be considered to be the nerve that controls facial expression, so when its function is disrupted, the control of facial expression is impaired.
While a number of different conditions can cause damage to the facial nerve, including tumors, trauma, toxins, and neurologic diseases, true Bell's palsy is an idiopathic (meaning that the cause is unknown) paralysis of the facial nerve. It typically occurs on one side of the face and comes on suddenly, sometimes overnight. The diagnosis of Bell's palsy is a diagnosis of exclusion, meaning that this diagnosis is made when all the potential other causes of nerve damage have been ruled out. Most investigators believe that Bell's palsy results from...