Facial nerve anatomy
Figure A: Facial nerve anatomy. The facial nerve is responsible for facial expression. The facial nerve begins in the brainstem, then takes a course through the temporal bone of the skull, before dividing into multiple branches within the face. Each branch provides specific movement. Click to enlarge.

Why Does Facial Paralysis Occur?

There are many causes of facial paralysis (more than 100!). Facial paralysis occurs when there is loss of facial movement. The facial nerve, or cranial nerve VII, controls facial movement (facial expressions). The facial nerve travels from the brain, through the skull (the temporal bone), and then divides into 5 main branches (supplying the forehead, eye, cheek and nose, mouth, and neck) as it courses through the cheek to the facial muscles (see Figure A). Interruption anywhere along this pathway can result in facial paralysis.

Some causes of facial paralysis improve and even resolve spontaneously and some do not, some are present at birth and some occur later in life. Facial paralysis may be associated with other differences or syndromes or occur in isolation. Facial paralysis may be unilateral (affecting one side of the face) or bilateral (affecting both sides) and may affect people of all ages. Paralysis may involve the entire face or only a portion of it.

Causes of Facial Paralysis

Cause Description or Example
Congenital Möbius syndrome, Vascular anomaly, Hemifacial microsomia, Goldenhar, Poland syndrome, Melkersson-Rosenthal, Other syndromes, No associated syndrome
Birth-related Traumatic or difficult delivery
Bell's Unknown cause, Viral infection
Traumatic Injury Temporal bone fracture, Blunt force to cheek, Laceration, Swelling involving facial nerve
Infectious Ear infections, Lyme disease, Viral infections (VZV (Ramsay Hunt), HSV, EBV), Mycoplasma, Mastoiditis
Neoplastic Central, Parotid, or Acoustic tumors
Iatrogenic Brain, Middle ear, and Facial surgery
Ischemic Loss of blood supply to the nerve or muscle
Neurogenic Guillan-Barré
Hematalogic LeukemiaHemophilia
Hypertension High blood pressure