Facial nerve palsy due to birth trauma is the loss of 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. Generally, the nerve has been damaged by pressure and the nerve fiber itself has not been torn. Therefore, the injury heals and the face returns to normal over a few weeks to months.

Most of the time the cause for such facial nerve palsy cannot be identified. Occasionally, however, a difficult delivery, with or without the use of instruments called forceps, may result in this condition.

Some factors associated with birth trauma (injury) include:

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

However, most mothers who have these factors do not deliver babies with facial palsy or birth trauma.

Damage to the facial nerve causes a loss of muscle movement (paralysis) to the side of the face stimulated by the nerve. The paralysis may affect the forehead to the chin in severe cases.

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 surrounding the lips. The defect is seen predominantly when the infant cries.

Since the facial muscles on the affected side are weak, the mouth is pulled towards the normal side during crying.

The following symptoms may be seen in the newborn infant:

• Lower lip does not move down the same way on both sides while crying (typical)
• No movement on the affected side of the face (total involvement, unusual)
• Eyelid may not close on affected side
• Lower face (below eyes) appears asymmetrical while crying

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 another problem (such as a stroke) is suspected.

In most cases, the infant will be closely monitored to see if the paralysis goes away on its own.

However, permanent paralysis requires special therapy.

The condition usually goes away on its own.

Permanent paralysis of facial muscles on the affected side occasionally occurs.

This condition is generally diagnosed while the infant is in the hospital. However, mild cases involving just the lower lip may not been seen at birth and can later be noticed by a parent, grandparent, or other person.

If the movement of your infant's mouth looks different on each side when he or she cries, you may want to call your health care provider.

There is no prevention for pressure injuries that occur to the unborn child. The proper use of forceps and improved childbirth techniques have reduced the rate of facial nerve palsy.