When should facial nerve injury be suspected in cases of facial and head trauma?

When to Suspect Facial Nerve Injury in Facial and Head Trauma

Suspect facial nerve injury immediately in any patient with facial or head trauma who presents with facial asymmetry, inability to close the eye, drooping of the mouth corner, or loss of forehead wrinkling, particularly when temporal bone fractures are present or when high-energy mechanisms are involved. 1, 2

High-Risk Mechanisms and Populations

• High-energy blunt trauma mechanisms automatically warrant suspicion for facial nerve injury, including motor vehicle collisions, significant falls, and assaults 1
• Facial nerve injury occurs in approximately 5-10% of all head-injured patients, making it the most frequently injured cranial nerve in head trauma 2, 3
• Male patients and adults in their 4th decade have peak incidence, with traffic injuries accounting for 82.5% of cases 3
• 68% of patients with facial fractures have associated head injuries, meaning concurrent evaluation is essential 1

Specific Clinical Signs Requiring Immediate Suspicion

Motor Function Assessment

• Complete inability to wrinkle the forehead (frontal wrinkling) is the most frequently deteriorated facial movement in facial nerve injury 4
• Inability to close the eye completely (lagophthalmos) indicates lower motor neuron facial nerve involvement 5, 4
• Drooping of the mouth corner or inability to smile symmetrically suggests facial nerve compromise 6, 4
• Asymmetry at rest with normal tone on the unaffected side differentiates peripheral from central lesions 6

Associated Symptoms

• Ipsilateral pain around the ear or face frequently accompanies facial nerve injury 6
• Dryness of the eye or mouth, taste disturbance, or hyperacusis indicate involvement of facial nerve branches to lacrimal glands, taste fibers, or stapedius muscle 6
• Paresthesia in the infraorbital nerve (V2) distribution suggests midface injury with potential facial nerve involvement 6, 1

Temporal Bone Fracture as Key Indicator

• Temporal bone fractures extending into the facial canal are the primary cause of traumatic facial nerve injury 2, 7
• Suspect temporal bone fracture when there is tenderness over the mastoid, hemotympanum, Battle's sign, or CSF otorrhea 1
• Frontal bone fractures occur in 5-15% of facial fractures and have 33% concomitant intracranial injury rate, requiring forces exceeding 1,000 kg 1

Critical Timing Considerations

• Immediate-onset complete facial paralysis (within 72 hours) suggests direct nerve transection or severe compression requiring urgent surgical evaluation 2, 7
• Delayed presentation of facial nerve paralysis can occur 3 days or more after initial trauma, necessitating follow-up evaluation even when initial examination is normal 2
• 70% of traumatic facial nerve palsies are lower motor neuron type, affecting all facial muscles including the forehead 3
• The left facial nerve is more frequently affected (60% of cases) in traumatic injuries 3

Systematic Evaluation Approach

Primary Survey First

• Complete airway, breathing, circulation stabilization before detailed facial nerve evaluation, as maxillofacial trauma can cause life-threatening airway compromise 1

Focused Facial Nerve Examination

• Palpate all facial bones for tenderness, particularly over the temporal bone and mastoid 1
• Test all facial nerve branches systematically: forehead wrinkling, eye closure strength, nasolabial fold symmetry, mouth movement, and smile 6, 4
• Assess for synkinesis (unintended eye closure with smile attempt), the most common sign of incomplete recovery 4
• Perform complete cranial nerve evaluation to identify associated nerve injuries 1
• Check for cerebrospinal fluid leak from nose or ear 1

Imaging Strategy When Facial Nerve Injury Suspected

• Obtain CT maxillofacial in addition to head CT when clinical signs of facial nerve injury are present 1
• High-resolution CT scans demonstrate temporal bone fractures extending into the facial canal, which newer generation scanners commonly identify 2
• Multidetector CT provides thin-section acquisitions and multiplanar reconstructions essential for surgical planning 1, 8
• MRI is reserved only for cranial nerve deficits not explained by CT or when evaluating nerve continuity 6, 8

Common Pitfalls to Avoid

• Do not dismiss normal initial facial nerve function—delayed paralysis can occur days after trauma 2
• Do not confuse Bell's palsy with traumatic facial nerve injury—Bell's palsy is a diagnosis of exclusion requiring no identifiable cause within 72 hours 6
• Do not rely on head CT alone—it detects 95% of facial fractures but often only partially images midface structures 8
• Do not delay otolaryngology consultation when facial nerve injury is identified, as timing determines surgical candidacy 2, 7

Prognostic Indicators Requiring Urgent Action

• Total or immediate paralysis has poor prognosis and warrants consideration for surgical repair 2
• Patients with extratemporal nerve transection require surgical exploration within 72 hours for optimal tension-free coaptation 7
• Start high-dose corticosteroids as early as possible in temporal bone fracture-related facial palsy 7
• Spontaneous total recovery occurs in only 30% of traumatic facial nerve injuries, with partial recovery in 12.3% 3