Bell palsy accounts for 80% of cases of unilateral lower motor neuron facial paralysis
It has an annual incidence of 20–30 cases per 100 000 population and can occur at any age; median age at onset is 40 years. The cause is unknown, although the herpes simplex viral genome is detected in the facial nerve endoneurial fluid in 79% of cases. Patients with Bell palsy should receive corticosteroids within 48 hours of symptom onset, regardless of severity
Treatment with a total of 450–500 mg prednisone over 10 days has a number needed to treat of 8 to achieve a House–Brackman score of grade 2 or less after 4 months for patients with severe or complete paralysis. Antiviral medications can be considered in severe cases. Eye protection (sunglasses, eye patch, lubricating tears or ointments) should be used routinely to prevent corneal abrasions, ulceration and keratitis. Other options for persistent symptoms include facial physiotherapy for weakness, botulinum toxin injections for facial asymmetry and surgery to facilitate eyelid closure.
More on the treatment of Bell’s Palsy via CMAJ.