Bell’s palsy is the most common condition affecting the facial nerve (Cranial Nerve VII) (1).
The annual estimate of people affected by Bell’s palsy is around 11-40 per 100,000 individuals(1) (2) affecting more than 60,000 Americans yearly(1).
Bell’s palsy, also known as facial nerve paralysis, is the weakness of the facial muscles supplied by the facial nerve of the affected side. The condition is acute in onset, idiopathic, unilateral, and maybe partial or complete. It is more common in the age group of 15-50 years and affects males and females in equal frequency(1).
Bell’s palsy is more common in pregnant women (in the third trimester or post-delivery), patients with diabetes and hypothyroidism, and the elderly(1).
How Does Bell’s Palsy Affect The Body?
The onset of Bell’s palsy signs and symptoms is sudden, usually within a few hours. The signs and symptoms include:
- Paralysis, weakness or numbness of the facial muscles of the affected side
- Loss of forehead wrinkling
- Drooping eyelid on the affected side
- Inability to close the eyelid leading to dry eye
- Excessive tearing of the eye
- Drooping of the corner of the mouth on the affected side
- Dribbling of saliva from the corner of the mouth on the ipsilateral side
- Impaired or altered taste sensation
- Difficulty eating from the affected side
- Ear pain on the ipsilateral side
- Hyperacusis (increased sensitivity to certain sounds) due to ipsilateral stapedial muscle dysfunction
Bell’s palsy may also lead to certain complications, which include crocodile tears, motor synkinesis (e.g. voluntary eye closure causing involuntary mouth movement), loss of taste sensation, slurred speech, facial muscle tightening and incomplete recovery(1), (2).
What Triggers Bell’s Palsy?
The actual cause of Bell’s palsy is unknown. However, the reactivation of dormant herpes viral infections, namely, herpes simplex virus (HSV-I) and herpes zoster virus (HZV), of the geniculate ganglia and their migration to the facial nerve is considered the most important trigger of Bell’s palsy(1)-3.
Other causes that have been implicated include different infections, inflammation (due to HSV-I) leading to nerve compression, autoimmune disorders (Hashimoto’s encephalopathy), intranasal influenza vaccine, and vascular (ischemia due to atherosclerosis leading to edema) causes.
Various infections include adenovirus, Epstein-Barr virus, Coxsackie virus, influenza, cytomegalovirus, rubella, mumps, and rickettsia. In about 4-8% of the patient’s family history has also been implicated(1), (2).
Management Of Bell’s Palsy
Since the exact cause of Bell’s palsy is still unknown, the objective of the treatment is to reduce the facial nerve inflammation and to decrease future complications associated with the disease, mainly eye complications. The management of Bell’s palsy is almost always medical rather than surgical due to risks associated with surgical decompression of the nerve, which includes seizures, facial nerve injury, cerebrospinal fluid leak, and unilateral hearing loss(1), (2).
The inability to close the eyelids and reduced tear production may lead to dry eyes and infections; therefore, to protect the eye and eye patch and eye lubricants become necessary to prevent corneal drying(1), (2).
Oral corticosteroid, mainly prednisolone, is the treatment of choice to reduce the inflammation associated with the facial nerve. Prednisolone, usually, is given at a dosage of 50-60 mg daily for 10 days in adults and a maximum of 80 mg in healthy adults. In diabetics, more than 120 mg/day is usually considered safe. Corticosteroids when started within 72 hours of symptoms commencement provide maximum benefit and faster recovery of normal facial functions(2).
The addition of antiviral drugs with corticosteroids has provided some benefit over the use of corticosteroids alone, but the evidence has been low quality. Since the recovery happens in more than 70% of patients without any treatment, the use of drugs remains controversial. Symptoms usually resolve within several weeks to 6 months; however, if the symptoms persist beyond 6-9 months, a referral becomes mandatory(2).