Bell’s palsy - Disorders of cranial nerves

Bell’s palsy

Definition

Idiopathic weakness of the muscles of facial expression.

Clinical features

Spontaneous unilateral weakness of the muscles of facial expression. As it is a lower motor neurone deficit, the forehead is affected and the eye may not be able to close completely. It usually begins to improve spontaneously after about 10 days, but may take months to recover completely.

Investigations

Electrophysiological tests may help to predict outcome: lack of evoked potential after 3 weeks has a poor prognosis.

Management

If the patient is unable to close their eye completely, artificial tears should be used and the eye taped shut at night to prevent corneal ulceration. The evidence for steroid treatment is weak but may have an effect if given within a day of onset. In cases that do not resolve tarsorrhaphy (suturing of upper to lower lid, laterally) may be necessary. Cosmetic surgery and/or reinnervation using a lingual nerve transfer for example, can be used for chronic cases.

Prognosis

A significant proportion do not completely resolve and it occasionally recurs.