Diagnosis Neurologist will look at your face and ask you to move your facial muscles by closing your eyes, lifting your brow, showing your teeth and frowning, among other movements. Other conditions — such as a stroke, infections, Lyme disease, inflammatory conditions and tumors — can cause facial muscle weakness that mimics Bell's palsy. If the cause of your symptoms isn't clear, your Neurologist may recommend other tests, including: • Electromyography (EMG). This test can confirm the presence of nerve damage and determine its severity. An EMG measures the electrical activity of a muscle in response to stimulation. It also measures the nature and speed of the conduction of electrical impulses along a nerve. • Imaging scans. Magnetic resonance imaging (MRI) or computerized tomography (CT) may be needed on occasion to rule out other possible sources of pressure on the facial nerve, such as a tumor or skull fracture. • Blood tests. There is no blood test for Bell's palsy. But blood tests can be used to rule out Lyme disease and other infections.