There are two major nerves in the face: the facial and trigeminal nerves. According to the Face and Emotion website, the facial, or seventh cranial nerve, carries the signals that control the muscles of expression of the face. The trigeminal, or fifth cranial nerve, is a large and complex nerve that is almost entirely sensory and reaches all parts of the face. Causes of damage to the nerves in the face include infection, trauma and tumor.
Bell's Palsy
There are five divisions of the facial nerve: temporal, zygomatic, buccal, mandibular and cervical, which are named for the area of the face that they innervate.
The facial nerve may become temporarily inflamed due to herpes simplex, Type 1 virus, which causes cold sores, or Borrelia burgdorferi, the spirochete that causes Lyme disease. Either of these infections can result in Bell's palsy, which is sudden paralysis of the upper and lower face. According to the National Library of Medicine, Bell's palsy accounts for about 75 percent of facial paralysis. The patient is unable to close the eye on the affected side and cannot wrinkle his brow or whistle. This condition usually resolves spontaneously in one to months. According to the National Institute of Neurological Disorders and Stroke, about 40,000 people in the United States develop Bell's palsy each year. It affects men and women equally. Most cases involve people 40 to 50 years old.
Other Causes
A corner of a person's mouth may be permanently asymmetric, which is called facial paralysis or droop. It may be due to birth trauma or an infection such as orbital cellulitis, a delay in treating bacterial meningitis with antibiotics or a brain tumor.
Acoustic Neuroma
According to Harrison's Principles of Internal Medicine, acoustic neuroma, or schwannoma, are tumors that arise most frequently in the acoustic nerve, or eighth cranial nerve. Acoustic neuroma can compress the facial nerve causing facial droop and hearing loss.
Trigeminal Neuralgia
There are three divisions of the trigeminal nerve: the opthalmic, the maxillary and the mandibular, which are named for the area of the face that they innervate.
Trigeminal neuralgia, also called tic douloureux, is of unknown cause and usually affects the elderly. Symptoms characteristically include stabbing pain in the region of the maxillary and mandibular nerves. Pain may be triggered by touching or washing the affected side of the face.
References
- Face and Emotion: Facial Nerves
- "Harrison's Principles of Internal Medicine"; Dennis Kasper, M.D.; 2005
- National Institute of Neurological Disorders and Stroke: Bell's Palsy Fact Sheet
- Medline Plus: Facial Paralysis
