Answer:
Bell’s palsy describes the idiopathic form of facial paralysis. It is a diagnosis of exclusion that should be made only after a thorough evaluation of the patient. Nonetheless, it is the most common diagnosis in patients with facial paralysis, with an incidence of 20 in 100,000 per year. The risk is higher in diabetics and during pregnancy. During pregnancy, facial paralysis most often occurs during the last trimester and usually resolves after delivery. The etiology is theorized to be a combination of viral-vascular insult to the facial nerve that causes edema of the nerve within the fallopian canal and ultimately disrupts the neural circulation. Prolonged anoxia in the compressed segment results in nerve degeneration. Concominant involvement of other nerves suggests that Bell’s palsy is a cranial polyneuropathy.
Treatment may involve no therapy, medical treatment, or surgical decompression. The natural course is for recovery to begin within 3 weeks in 85% of patients but not for 3 to 6 months in the remaining 15%. The longer recovery is delayed, the higher the incidence of sequelae such as synkinesis and “contracture.” Overall, approximately 71% of patients with total facial paralysis recover without sequela. The aim of medical therapy is to reduce edema and restore circulation to the nerve. Steroids within 24hrs of onset appear to significantly improve facial grade at recovery and lessen denervation. Side effects occur in less than 4%. Surgical decompression involves removal of the bony covering of the fallopian canal through 180 degrees of its circumference, with or without incision of the periosteum-epineurium. The decision to decompress selected patients is based on one or more electrical prognostic tests. Many surgeons have abandoned decompression altogether.