Bell's palsy is also known as Facial Nerve Paralysis. Bell's palsy is a form of facial paralysis resulting from trauma or damage to the facial nerve. It usually affects one side of the face. In less than 1 % of all, cases the paralysis may affect both sides of the face at once. Bellâ€™s palsy is named after a Scottish doctor, Dr. Charles Bell, who first described the condition in 1882.
Bell's palsy accounts for about half of all cases of paralysis affecting the face. This condition appears suddenly with no obvious cause. Most cases occur among people over the age of 40, but it can affect all age groups, including children. Men and women are equally affected. Pregnancy increases the risk. Over 80% of cases clear up without treatment within few weeks.
Anatomy of Facial nerve
Facial nerve is the 7th nerve among the 12 cranial nerves. Most of the muscles of the face are controlled by the facial nerve.The facial nerve emerges as two roots from the anterior surface of the hindbrain between the pons and the medulla oblongata. Along its course the facial nerve supplies the muscles of the face, the cheek, the scalp, stylohyoid, posterior belly of the digastric muscles of the neck and the stapedius muscle of the middle ear.
The sensory root carries taste fibers from the anterior two thirds of the tongue, floor of the mouth and the palate.
The parasympathetic secretomotor fibers supply the submandibular and sublingual salivary glands, the lacrimal glands and the glands of the nose and palate.
Functions of Facial nerve
- controls facial expression
- controls salivation and lacrimation
- Responsible for taste sensations
- Responsible for muffling of the sounds heard.
The exact causes of Bell's palsy is not known. The following conditions are known to lead to Bell's palsy:
- Viral infections such as measles, mumps, chicken pox and infectious mononucleosis.
- Bacterial infections such as Lyme disease, syphilis, meningitis, tuberculosis and ear infection.
- Individuals with diabetes, influenza or other upper respiratory tract infections are at increased risk.
- Tumors causing nerve compression, injury to the head or face and neurological disorders such as Guillain-Barre syndrome, multiple sclerosis and myasthenia gravis.
The severity of symptoms depends on the extent of facial nerve damage and varies from mild weakness to complete paralysis. Symptoms usually appear suddenly following a recent upper respiratory tract infection or other viral infections, with a sudden pain around the ears, leading to weakness or paralysis of one side of the face. Other symptoms include:
- Inability to blink or close the eye..
- Drooling and changes in the amount of tears.
- Dryness of eye and mouth.
- Loss of taste in the front portion of the tongue.
- Droopiness of the face on the affected side and difficulty in facial expressions.
- Facial stiffness and twitching.
- Hypersensitivity to sound.
- Impaired speaking.
Bell's palsy is self-limiting. Symptoms do not spread beyond the face. Between 60-80% of patients experience complete recovery within few days to few months depending upon the extent of damage of the facial nerve. Recurrence occurs in rare cases.
The Diagnosis is based on the history, symptoms and ruling out other disorders. Thorough examination of the head, neck, ears and eyes, to check for any weakness or impaired movement. Other diagnostic tests used to rule out Bell's palsy are as follows:
- CT (computer tomography) and MRI (magnetic resonance imaging) are used to detect abnormalities in and around the facial nerve.
- Hearing tests should be performed to detect is there is any damage to the nerve responsible for hearing. Tests to evaluate the eyes ability to produce tears and to evaluate the sense of taste should also be performed.
- EMG (electromyography) is performed to assess the disease progression and the extent of injury.
- Laboratory tests are performed to find out the underlying causes as bacterial infections.
There is no curative treatment for Bell's palsy. It includes the following:
- Continuous eye care is required because the patients are unable to blink or close their eyelids completely. This may lead to permanent damage of the eyes. During the day, artificial tears are instilled in the eye about every two hours to keep the moisture and let out the debris. At nighttime, a heavy lubricant is placed in the eye and the eyelid is taped shut to reduce dryness and the risk for injury.
- Treatment with corticosteroids such as prednisone is used to reduce inflammation and swelling of the facial nerve.
- Antiviral agents such as acyclovir maybe used. The combination of acyclovir and prednisone is proven to be more effective than prednisone alone.
- Surgical treatment is indicated if there is no complete recovery of the disease. Surgical procedures such as, facial nerve repair and nerve graft, nerve substitution and muscle transposition are performed in order to improve facial function and appearance.
- Physical therapy called facial training improves muscle mobility and minimizes the asymmetrical appearance of the face.
- Facial exercises and massage may improve muscle tone and help the facial nerve to recover.