Symptoms:

• Hearing loss on one side
• Painful rash on the eardrum, tongue, or roof of the mouth (palate) on the same side as the facial weakness
• Sensation of things spinning around (vertigo)
• Weakness of the face with difficulty closing one eye -- smile may look crooked

Signs and tests:

The doctor will usually make the diagnosis by looking for signs of weakness in the face and a blister-like (vesicular) rash. Some patients will have a nerve conduction study to find out how much damage has been done to the facial nerve and to see how well they will recover.

Blood tests can help determine whether you have been infected with the varicella zoster virus.

There is a promising laboratory technique called PCR, which can detect very small amounts of the virus's DNA in the skin. However, it is mostly used for research.

The use of pictures of the brain (neuroimaging), such as magnetic resonance imaging (MRI), may show swelling of the facial nerves and help the doctor find out whether the infection has spread to other nerves or the brain. A spinal tap is used in rare cases, especially when the diagnosis is not clear.