the patient's facial nerves are functioning is reported as a fraction of the 6 levels. Therefore, someone with normal facial nerve integrity would be reported as "1/6," or "level 1 of 6." Grade two is associated with mild weakening of the facial nerve, and grades three and four have moderate damage, varying only on the basis of the ability to close the eye. The next two levels include severe impairment and total paralysis, respectively. Electroneuronography may only be employed in the most severe instances (5/6 or 6/6) because in the other cases there is clear evidence that the nerve is mostly intact. Even so, it may be helpful to chart a patient's progress beginning at the lowest levels of damage. Common Causes of Weakness Perhaps the most common cause of damage to the facial nerve is Bell's palsy (BP). It has a reported incidence of about 0.00015% within the world population each year, and in up to approximately 10% of those cases, the disorder will recur. The etiology of this disease is currently unknown, but hypotheses include infections, genetic predisposition, environmental factors, and neuropathy. Among those who develop the disorder, unilateral paralysis of the facial muscles occurs in a day or two, but it is common for the patient to recover on their own over the span of a few weeks. Even if the condition is resolved, the patient still stands a 20% chance of having lifelong weakness in their facial muscles, and 5% of these people will have permanent damage equivalent to a level of 4 or higher on the House-Brackmann scale. Another possible effect of Bell's palsy is Wallerian degeneration (WD), which may take days to become evident. Because of the slow-acting nature of this pathology, a patient may present healthy electroneuronography results despite a lack of volitional control of the facial muscles immediately following the onset of Bell's palsy. This is because the degeneration has not yet reached completion, and some fibers are still intact. Therefore, it is standard procedure to wait at least three days after symptoms present themselves to perform an electroneuronography test, in order to prevent false negatives. At the other end of the spectrum, tests are generally not recommended after a period of twenty-one days. Typically, electroneuronography recordings are taken on the third day of symptoms and repeated every four days until a plateau is reached. Facial Nerve Injury Seddon classified facial nerve