10 Minute consultation: Bell's palsy

What issues you should cover

Associated symptoms— Patients with Bell's palsy commonly feel pain in or behind the ear. Numbness can occur on the affected side of the face. Loss of taste on the ipsilateral anterior two thirds of the tongue is common. Ask about associated hyperacusis and any presence of rash that may indicate herpes zoster.

Cause— Ask about recent viral infection and recent immunisation. The causes of Bell's palsy are unknown, but the possibilities include viral infection, heredity, autoimmune or vascular ischaemia, of which the most likely cause is viral.

Incidence— Bell's palsy is commonest in the age group 10 to 40 years. Each year about 20 cases per 100 000 people occur.

What you should do

You will need to differentiate between an upper and lower motor neurone lesion of the facial nerve. A lower motor neurone lesion occurs with Bell's palsy, whereas an upper motor neurone lesion is associated with a cerebrovascular accident. A lower motor neurone lesion causes weakness of all the muscles of facial expression. The angle of the mouth falls. Weakness of frontalis occurs, and eye closure is weak. With an …