The Five Senses and Beyond: The Encyclopedia of Perception - Jennifer L. Hellier 2017

Bell’s Palsy

Bell’s palsy is a peripheral nerve disorder affecting the facial nerve, or cranial nerve VII. While the exact mechanism of Bell’s palsy is unknown, it is thought to be caused from edema (swelling) and inflammation of the facial nerve. It is characterized by unilateral (one side) and temporary weakness or total paralysis of the facial nerve, which originates in the brainstem and is responsible for controlling the muscles of facial expression and for the sense of taste from the anterior two-thirds of the tongue. Cranial nerve VII also provides innervation to lacrimal glands (tears), salivary glands, and the stapes (a bone in the middle ear used for hearing). Patients with Bell’s palsy suffer a temporary inability to control the muscles of the face that include movements like smiling and raising eyebrows. Bell’s palsy occurs in approximately 40,000 people in the United States each year and is most common among 15- to 60-year-olds (NINDS, 2012).

History

Disorders of facial nerve paralysis have been recorded in medical texts as early as the Persian physician Rhazes (865—925) who described the disorder in his text al-Hawi. It was later described by authors in the Greek and Roman empires and then later by European physicians in the 17th and 18th centuries. Bell’s palsy is formally named after Scottish physician Sir Charles Bell (1774—1842) after he introduced the disorder to the Royal Society of London in 1829.

Diagnosis and Symptoms

Bell’s palsy is diagnosed when a person suffers acute onset, unilateral, hemifacial weakness or paralysis with no other signs or symptoms and no other disorder can be attributed to the facial weakness or paralysis. It is not thought to be infectious, although some researchers are still investigating viral etiology. Bell’s palsy is more common during pregnancy and in people who suffer from obesity, diabetes, hypertension, upper respiratory infections, or compromised immune systems. Patients with Bell’s palsy usually recover completely, although some may never fully recover. Bell’s palsy is a diagnosis of exclusion, meaning that all other disorders must be ruled out before a diagnosis of Bell’s palsy can be given. Differential diagnoses for Bell’s palsy that must be considered include stroke, herpes zoster virus (Ramsay Hunt syndrome type 2), Lyme disease, HIV (human immunodeficiency virus) infection, head trauma, tumors, meningitis, and inflammatory diseases of the cranial nerves such as sarcoidosis or brucellosis. Both physicians and dentists in the United States are trained in the diagnosis, treatment, and management of Bell’s palsy.

There are both short-term and long-term signs and symptoms of Bell’s palsy including:

•Unilateral facial weakness or paralysis

•Inability to smile and raise eyebrows on affected side

•Inability to close eye on affected side

•Alteration of taste

•Difficulty chewing food

•Numbing or tingling in cheek or mouth

•Dryness of the affected eye

•Corneal ulceration

•Vision loss

•Permanent facial disfigurement

•Ringing in the ears

•Headache

•Dizziness

•Impaired speech

•Depression

•Acute and rapid onset within 72 hours

•No other disorder, tumor, or illness can be identified

Treatment

The current treatment of choice for patients with Bell’s palsy is oral corticosteroid treatment and antiviral treatment, although antiviral treatment has not been found to have a clear benefit to Bell’s palsy patients. Physicians most commonly prescribe a six-month course of prednisone, and the most common antivirals prescribed are acyclovir or valacyclovir. It is recommended to begin treatment within three days of onset of symptoms for optimal results.

Physical therapy is also recommended to reduce the symptoms of Bell’s palsy and may be helpful in some patients. Physical therapy stimulating the facial nerve aids in maintaining muscle tone and reeducating the muscles of facial expression so they may return to the most normal functioning upon recovery. Palliative treatment and eye care are crucial in preventing overdrying of the eye and eventual loss of vision. Frequent lubrication and protection with an eye patch of the affected eye is recommended. Heat application has been shown to reduce pain associated with Bell’s palsy in some patients. Surgical decompression of the facial nerve has been done but has not been shown to be beneficial in most patients. Surgery is no longer recommended by the American Academy of Neurology. Finally, most persons will recover within three to four months after the initial signs.

Elizabeth Shick

See also: Dizziness; Facial Nerve; Ptosis

Further Reading

Baugh, Reginald F., Gregory J. Basura, Lisa E. Ishii, Seth R. Schwartz, Caitlin Murray Drumheller, Rebecca Burkholder, … William Vaughan. (2013). Clinical practice guidelines for Bell’s palsy. Otolaryngology—Head and Neck Surgery, 149(3), S1—S27.

Gronseth, Gary S., & Remia Paduga. (2012). Evidenced-based guideline update: Steroids and antivirals for Bell palsy. Neurology, 79(22), 2209—2213.

National Institute of Neurological Disorders and Stroke (NINDS). (2012). Bell’s palsy fact sheet. Retrieved from http://www.ninds.nih.gov/disorders/bells/detail_bells.htm

Ragupathy, Kalpana, & Eki Emovon. (2013). Bell’s palsy in pregnancy. Archives of Gynecology and Obstetrics, 287, 177—178.