Bell's palsy is usually diagnosed from a medical history, a physical exam, and a neurological exam that checks facial nerve function and rules out more serious causes of facial paralysis.

Your doctor will decide whether you could have Bell's palsy by asking you questions about your medical history, such as:

• What are your symptoms? When did you first notice them? Have you ever had them before?
• Have you recently had a head injury?
• Do you have pain or loss of feeling in your face or head area?
• Have you had any other problems, such as dizziness, hearing loss, changes in your ability to taste, or weakness in any other part of your body?

During a neurological exam, your doctor will evaluate your muscle weakness. You may be asked to:

• Lift your eyebrows and then lower them.
• Close your eyes tightly and then open them.
• Smile or show your teeth.

Bell's palsy may be diagnosed when you have:

• Weakness and paralysis that develop suddenly and affect the muscles on one side of your face.
• No signs of any other disease or injury that might explain the weakness and paralysis.

Weakness that occurs on one side of your face should be checked by a doctor right away to rule out more serious conditions. Early detection and treatment of Bell's palsy may help prevent permanent nerve damage.

Your doctor may order additional tests to look for other possible causes of your facial weakness and paralysis. These tests include:

• Blood tests, to rule out diseases such as Lyme disease, HIV, or syphilis.
• Hearing tests, to determine whether your hearing or the muscles in your middle ear are affected.
• A CT scan or MRI, to check for a brain tumor or stroke.
• A lumbar puncture, to check for signs of infection or bleeding.