Facial Nerve Problems
The most common condition resulting in facial nerve weakness or paralysis is Bell’s Palsy, named after Sir Charles Bell who first described the condition. The underlying cause of Bell’s Palsy is not known, but it is speculated to frequently involve viral infection (e.g. herpes). The mechanism of facial weakness involves inflammation of the nerve, causing it to swell in its tight bony canal as it passes through the skull base from the brainstem to the face. This swelling results in pressure on the nerve fibers and their blood vessels.
“Bell’s Palsy” is a diagnosis of exclusion, meaning the term is used only after thorough neurotologic and general evaluation to rule an identifiable cause, such as tumor compressing the nerve. Tests are often employed, including hearing testing (since the facial nerve travels next to the hearing nerve), facial function tests, and imaging studies (e.g. MRI or CT scans). Treatment is directed at decreasing the swelling and restoring the circulation so that the nerve fibers may again function normally. Medicines such as steroids, and sometimes antiviral medications, are usually employed. In rare instances, surgical intervention to “decompress” the nerve and allow return of blood flow to the nerve fibers may be indicated. However, medical therapy and decompression are most effective if performed early after the onset of the paralysis (i.e. 2 weeks), for which reason patients are encouraged to be seen by a physician as soon as possible. Fortunately, true Bell’s Palsy is associated with a high level of recovery.
Herpes Zoster Oticus
A condition similar to Bell’s Palsy is Herpes Zoster Oticus, or “shingles”, of the facial nerve. In this condition, there is not only facial weakness, but also often hearing loss, unsteadiness, and painful blisters in the ear canal. These additional symptoms usually subside spontaneously, but some hearing loss and discomfort may remain. The chances of recovery are reduced with Herpes Zoster Oticus compared to Bell’s Palsy.
Injuries of the Facial Nerve
The most common cause of facial nerve injury is fracture of the skull base. This injury may occur immediately or may develop some days later due to nerve swelling.
Injury to the facial nerve may occur during operations on the ear. This complication, fortunately, is very uncommon. The risk is higher when the nerve is not in its normal anatomical position (congenital abnormality) or when the nerve is so distorted by mastoid or middle ear disease that it is not identifiable. In rare cases it may be necessary to remove a portion of the nerve in order to eradicate the disease.
Delayed weakness or paralysis of the face following reconstructive middle ear surgery (myringoplasty, tympanoplasty, stapedectomy) is uncommon, but occurs at times due to swelling of the nerve during the healing period. Fortunately, this type of facial nerve weakness usually subsides spontaneously in several weeks and rarely requires further surgery.
Tumors: Acoustic Tumors
The most common tumor to involve the facial nerve is a nonmalignant fibrous tumor of the hearing and balance nerve called an acoustic neuroma. Although there is rarely any weakness of the face before surgery, tumor removal sometimes results in weakness or paralysis of the same side of the face due to the close proximity of the tumor to the facial nerve. This weakness usually improves or subsides in several months without treatment, but can leave a permanent weakness.
Tumor: Facial Nerve Neuroma
A nonmalignant fibrous growth may occur in the facial nerve itself, producing a gradually progressive facial nerve paralysis. Removal of a facial nerve neuroma may necessitate removal of the inner ear structures. If this is necessary, it results in a total loss of hearing in the operated ear and temporary severe dizziness. Persistent unsteadiness is uncommon.
Rehabilitation of Cut Nerve
It may be necessary to sever or remove a portion of the facial nerve in order to remove an acoustic tumor or a facial nerve neuroma. An attempt is made to suture the nerve ends together at the time of surgery or to insert a nerve graft. The nerve used in grafting is taken from a skin sensation nerve in the neck. Total paralysis will be present until the nerve regenerates through the graft, usually over a period of 6 to 24 months. At times, a nerve procedure is necessary later, connecting a tongue nerve to the facial nerve (hypoglossal-facial nerve anastomosis). In all of these situations, there will be some degree of permanent facial weakness. Other rehabilitative measures for facial weakness can include placement of a gold weight in the eyelid to assist in closure with blinking, and cosmetic procedures designed to reduce drooping of the face.
Acute or chronic middle ear or mastoid ear infections occasionally cause a weakness of the face due to swelling or direct pressure on the nerve. In acute infections, the weakness usually subsides as the infection is controlled and the swelling around the nerve subsides.
Facial nerve weakness occurring in chronically infected ears is usually due to pressure from a cholesteatoma (skin-lined cyst). Mastoid surgery is performed to eradicate the infection and cholesteatoma, and to relieve nerve pressure. Some permanent facial weakness may remain.
Tumors and circulatory disturbances of the nervous system may cause facial nerve paralysis. The most common example of this is a stroke. As opposed to most other conditions causing facial weakness, in brain diseases there are usually many other symptoms which indicate the brain as the cause of the problem. Treatment is managed by our neurotologists in conjunction with an internist, neurologist, or neurosurgeon.
Hemifacial spasm is an uncommon disease which results in spasmotic contractions of one side of the face. Extensive investigation is necessary at times to establish the diagnosis correctly. In some cases, a hemifacial spasm is caused by an irritation of the facial nerve by a blood vessel near the brain. Examination of the nerve and correction of the irritation, if present, is possible by a surgical approach.