The most common symptoms are facial weakness or paralysis, a dry eye or mouth, and problems tasting. The severity of symptoms depends on the extent of facial nerve damage and varies from mild weakness to complete paralysis. Bell’s palsy usually affects both the upper and lower parts on one side of the face. Both sides of the face are affected in less than 1% of cases.
In addition to paralysis, other symptoms include:
- Dry mouth
- Facial twitching
- Hypersensitivity to sound
- Inability to blink or close the eye, tearing, and dry eyes
- Impaired sense of taste
A diagnosis of Bell’s palsy is often based on symptoms and by ruling out other disorders. Other conditions that may cause facial paralysis include facial tumors, certain cancers, and autoimmune diseases. The physician can usually exclude other disorders by taking the patient’s history of symptoms, and by examining the head, neck, ears, and eyes. Imaging tests such as computerized tomography (CT scan) or magnetic resonance imaging (MRI scan) are used to detect infection, tumor, bone fracture, or other abnormality in and around the facial nerve. Hearing and balance tests are used to determine if the nerve responsible for hearing is also damaged and assess injury to the inner ear. The sense of taste also can be evaluated to determine the location and severity of a facial nerve lesion. Electromyography (EMG) assesses injury by electrically stimulating the facial nerve. Electrical current is applied to the skin over the nerve and nerve function is determined by the amount of current needed to cause contraction of the facial muscles. The test is often repeated to assess disease progression and the extent of injury. Laboratory tests can help the physician determine the underlying cause. For example, a blood test for Lyme disease may be ordered if there is a chance that the patient was bitten by a deer tick.
Medications and non-medication treatment are used to improve recovery.