Facial nerve palsy due to birth trauma is the loss of controllable (voluntary) muscle movement in an infant's face due to pressure on the facial nerves just before or at the time of delivery.

The infant's facial nerve (also called the seventh cranial nerve) can be damaged just before or at the time of delivery.

Most of the time the cause is unknown. However, a difficult delivery, with or without the use of instruments called forceps, may lead to this condition.

Some factors that can cause birth trauma (injury) include:

• Large baby size (may be seen if the mother has diabetes)
• Long pregnancy or labor
• Use of epidural anesthesia
• Use of a medication to cause labor and stronger contractions

However, most of the time these factors do not lead to facial nerve palsy or birth trauma.

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).