Bell's palsy

Bell's palsy is the most common cause of facial paralysis which results from damage to the facial nerve (cranial nerve VII). Facial nerves are normally paired. Usually in Bell's palsy, only one of the pair is affected resulting to paralysis or weakness of one side of the face. ^[1]

Epidemiology

Bell's palsy may develop in any age but the usually affected are adults. ^[2]

Causes

The exact reason is not yet understood. Most often, Bell's palsy is linked to viral exposure. Viruses associated with the condition include herpes simplex (genital herpes), herpes zoster (shingles), adenovirus (respiratory illnesses), rubella (German measles), mumps virus (mumps), influenza B (flu) and coxsackievirus (hand-food-and-mouth disease. ^[3] Bell's palsy has also been associated to Lyme disease. ^[2]       

Factors that may increase the likelihood of getting Bell's palsy are pregnancy, diabetes and flu. ^[4]

Symptoms

The main symptom of Bell's palsy is a sudden one-sided facial weakness or paralysis causing facial muscles to droop. The patient may experience difficulty closing the eye on the affected side. Other symptoms to watch for are drooling, excessive tearing or dry eyes, ear pain, increased sensitivity to sound on the affected side, numbness in the affected side and taste impairment. ^[5] On rare cases, both sides of the face are affected. Symptoms often start suddenly with peak taking place within 48 hours. ^[1]

Diagnosis

History is carefully taken. To assess the facial nerve, physical and neurological exams are done. ^[5] The physician might also test for Lyme disease and other infections. Depending on the manifestations, imaging studies may be requested such as CT scans, x-ray and MRI. To test for muscle response to nerve signals, electromyography (EMG) is done. ^[5]

Treatment

Symptoms often go away on their own but it may take weeks or months for facial muscles to get stronger. ^[6] To reduce inflammation, corticosteroid is often prescribed. If there is underlying viral infection, antiviral drug may be indicated although there is no clear evidence to support this. ^[5] When there is difficulty closing an eye, the physician often recommends eyedrops, eyepatch or protective glasses. ^[2]

Prognosis

3 out of 4 patients get better without treatment. With or without treatment, improvement is usually within 2 weeks with complete recovery commonly taking place within 3 to 6 months. ^[4]

Muscle weakness and other problems might be permanent in some cases.

References:

1. http://www.ninds.nih.gov/disorders/bells/bells.htm

2. http://kidshealth.org/teen/diseases_conditions/brain_nervous/bells_palsy.html

3. http://www.mayoclinic.com/health/bells-palsy/DS00168/DSECTION=causes

4. http://www.nlm.nih.gov/medlineplus/bellspalsy.html

5. http://www.webmd.com/brain/tc/bells-palsy-topic-overview

6. http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001777/