What is the primary concern after a left stylomastoid foramen injury during a forceps delivery?

Facial Nerve Paralysis Following Left Stylomastoid Foramen Injury During Forceps Delivery

Injury to the left stylomastoid foramen during forceps delivery will result in ipsilateral facial nerve paralysis affecting all muscles of facial expression on the left side of the face. 1

Anatomical Basis

• The facial nerve (CN VII) exits the skull base through the stylomastoid foramen before branching to innervate the muscles of facial expression 1
• Forceps blades can cause direct compression injury to the nerve at this vulnerable exit point 2, 3
• This location represents the extracranial segment of the facial nerve after it has traversed through the temporal bone 1

Clinical Presentation

• Unilateral weakness or paralysis of all facial muscles on the affected (left) side 1, 2
• Inability to close the eye completely (lagophthalmos) 1, 2
• Flattened nasolabial fold on the affected side 2, 3
• Drooping of the corner of the mouth 2, 3
• Asymmetric facial movements, particularly noticeable during crying 2, 3

Severity and Classification

• Most cases of forceps-related facial nerve palsy are classified as mild to moderate according to the House-Brackmann scale 2
• The severity depends on the degree of compression and whether the injury is a neurapraxia (temporary) or more severe axonotmesis/neurotmesis 2, 3

Natural History and Prognosis

• The vast majority (89-100%) of neonatal facial nerve palsies due to forceps injury resolve spontaneously 2, 3
• Average recovery time is approximately 24 days 2
• Complete recovery typically occurs within 1-3 months 3
• Only a small percentage (approximately 7-11%) may have incomplete recovery with residual weakness 3

Management

• Observation is the mainstay of treatment as most cases resolve spontaneously 2
• Eye protection is crucial if there is incomplete eye closure:
  • Lubricating eye drops during the day 1
  • Lubricating ointment and eye taping at night if needed 1
• Corticosteroid treatment is generally not required for birth-related facial nerve palsy 2
• Surgical intervention is rarely indicated for these cases 2

Prevention

• The use of a single forceps blade as a lever during delivery is considered dangerous and should be avoided 1
• Proper training in forceps application techniques is essential to minimize risk of nerve injury 1
• High-fidelity simulation training for difficult deliveries can help reduce complications 1

Associated Injuries to Consider

• Other cranial nerve injuries may coexist, particularly in cases of difficult extraction 4
• Corneal trauma may occur concurrently with facial nerve injury during forceps delivery 4
• Intracranial hemorrhage should be considered if there are additional neurological deficits 4

Long-term Considerations

• Parents should be counseled about the generally favorable prognosis 2, 3
• Regular follow-up is recommended until complete resolution is observed 2
• If no improvement is seen within 3-4 weeks, further neurological evaluation may be warranted 3

Forceps-related facial nerve palsy represents one of the most common birth-related nerve injuries, but fortunately carries an excellent prognosis in most cases 2, 3.