The most common form of facial nerve palsy due to birth trauma involves only the lower part of the facial nerve. This area controls the muscles around the lips. The defect is seen mainly when the infant cries.

The newborn infant may have the following symptoms:

• Eyelid may not close on affected side
• Lower face (below eyes) appears uneven during crying
• Mouth does not move down the same way on both sides while crying
• No movement (paralysis) on the affected side of the face (from the forehead to the chin in severe cases)

A physical exam is usually all that's needed to diagnose this condition. Rarely, a nerve conduction study is needed. Such a test can pinpoint the exact location of the nerve injury.

Brain imaging tests are not needed unless the health care provider suspects another problem (such as a stroke).