Infection
Lyme disease, an infection caused by Borrelia burgdorferi bacteria and spread by ticks, can account for about 25% of cases of facial palsy in areas where Lyme disease is common. In the U.S., Lyme is most common in the New England and Mid-Atlantic states and parts of Wisconsin and Minnesota, but it is expanding into other areas. The first sign of about 80% of Lyme infections, typically one or two weeks after a tick bite, is usually an expanding rash that may be accompanied by headaches, body aches, fatigue, or fever. In up to 10-15% of Lyme infections, facial palsy appears several weeks later, and may be the first sign of infection that is noticed, as the Lyme rash typically does not itch and is not painful. Lyme disease is treated with antibiotics.Reactivation of herpes zoster virus, as well as being associated with Bells palsy, may also be a direct cause of facial nerve palsy. Reactivation of latent virus within the geniculate ganglion is associated with vesicles affecting the ear canal, and termed Ramsay Hunt syndrome type II. In addition to facial paralysis, symptoms may include ear pain and vesicles, sensorineural hearing loss, and vertigo. Management includes antiviral drugs and oral steroids. Otitis media is an infection in the middle ear, which can spread to the facial nerve and inflame it, causing compression of the nerve in its canal.
In the best case scenario, paralysis can be corrected with techniques including hypoglossal-facial nerve anastomosis, end-to-end nerve repair, cross facial nerve grafting, or muscle transfer/transposition techniques, such as the gracilis free muscle transfer. Patients with facial nerve paralysis resulting from tumours usually present with a progressive, twitching paralysis, other neurological signs, or a recurrent Bells palsy-type presentation. The latter should always be suspicious, as Bells palsy should not recur. A chronically discharging ear must be treated as a cholesteatoma until proven otherwise; hence, there must be immediate surgical exploration. Computed tomography (CT) or magnetic resonance (MR) imaging should be used to identify the location of the tumour, and it should be managed accordingly. Other neoplastic causes include leptomeningeal carcinomatosis. Stroke
Central facial palsy can be caused by a lacunar infarct affecting fibers in the internal capsule going to the nucleus. The facial nucleus itself can be affected by infarcts of the pontine arteries. Unlike peripheral facial palsy, central facial palsy does not affect the forehead, because the forehead is served by nerves coming from both motor cortexes. Other
Other causes may include:

Diabetes mellitus
Facial nerve paralysis, sometimes bilateral, is a common manifestation of sarcoidosis of the nervous system, neurosarcoidosis. Bilateral facial nerve paralysis may occur in Guillain–Barré syndrome, an autoimmune condition of the peripheral nervous system. Moebius syndrome is a bilateral facial paralysis resulting from the underdevelopment of the VII cranial nerve (facial nerve), which is present at birth.