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Questions and Answers
What characterizes a Grade II dysfunction in facial function?
At what grade level does the eye show incomplete closure for the first time?
Which statement accurately describes the mouth function in Grade III dysfunction?
What is the primary facial feature affected in Grade V dysfunction?
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In which grade does facial dysfunction start to show an asymmetry that is described as obvious but not disfiguring?
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What is the purpose of facial nerve testing?
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Which type of test can determine the site of facial nerve injury but does not predict recovery function?
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Which lesion site results in impaired lachrymation, stapedial reflex, taste, and salivation?
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What does a pure motor deficit indicate when assessing levels of facial nerve injury?
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What does a Schirmer's test measure?
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What happens if there is a lesion between the nerve to stapedius and chorda tympani?
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Which imaging test is rarely done for traumatic facial nerve injury but offers better visualization of soft tissue conditions?
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What is the primary benefit of identifying potential recovery of function in facial nerve injuries?
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What is a common effect of facial nerve injury caused by penetrating trauma to the temporal bone?
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Which condition involves sensorineural hearing loss due to damage to the 8th cranial nerve?
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What is the most common surgical procedure resulting in facial nerve paralysis?
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What percentage of cases involve unrecognized injury to the facial nerve during surgery?
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Which type of fracture is classified as a transverse fracture in CT imaging?
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Which are common symptoms associated with facial nerve injury?
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How is sensorineural hearing loss characterized in cases involving concussion?
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What is a typical result of gunshot wounds to the temporal bone?
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What grading system is used to assess facial movement after nerve injury?
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What is a characteristic sign of haemotympanum during physical examination?
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What is the primary purpose of the nerve excitability test (NET)?
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Which statement about the maximal stimulation test (MST) is correct?
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What is one of the primary disadvantages of electroneurography (ENoG)?
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During electromyography, what indicates a normal muscle activity?
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How is the degree of facial nerve degeneration determined using ENoG?
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What does a response rated as 'markedly decreased' in the maximal stimulation test imply?
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What is a significant drawback of the nerve excitability test (NET)?
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For a patient with 90% degeneration in ENoG, what surgical intervention is typically warranted?
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Which of the following is considered a dynamic reconstruction procedure for facial nerve trauma?
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What does a polyphasic potential recorded in electromyography indicate about muscle recovery?
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What must be communicated to the patient before surgery regarding expected outcomes?
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What is considered a good prognosis if nerve response is assessed?
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What should be done if loss of function is noted after surgery?
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What indicates the need for immediate surgical exploration in the case of facial nerve injury?
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When should delayed exploration be performed for gunshot wounds?
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What surgical approach should be used when the site of the facial nerve injury cannot be localized preoperatively?
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What is recommended to drain during the facial nerve decompression procedure if identified?
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What is the purpose of neurolysis in facial nerve surgery?
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Which of the following is an indication that further exploration is warranted?
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What should be used to prevent thermal injury during facial nerve decompression?
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Grade IV dysfunction presents with no forehead movement and incomplete closure of the eye.
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In Grade V dysfunction, there is complete closure of the eye with minimal effort.
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Grade II facial dysfunction shows a moderate difference in forehead movement.
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Obvious asymmetry becomes noticeable at rest in Grade III facial dysfunction.
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Grade VI dysfunction is characterized by significant functional weakness with apparent facial asymmetry.
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The mastoid segment of the facial nerve gives off branches to the cochlear nerve.
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Class IV Sunderland nerve injury classification indicates that the epineurium is disrupted while the perineurium remains intact.
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Temporal bone fractures are the leading cause of facial nerve paralysis after Bell's Palsy.
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The labyrinthine segment of the facial nerve runs in the widest portion of the internal auditory canal.
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In Sunderland Class II nerve injury, Wallerian degeneration occurs proximal to the site of injury.
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Study Notes
Facial Nerve Trauma
- Causes: Lacerations, fractures of the temporal bone, penetrating trauma (gunshot wounds), iatrogenic injury (surgery, forceps delivery),
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Complications:
- Sensorineural Hearing Loss
- Haemotympanum (Conductive Deafness)
- Facial Palsy
- Vertigo
- Labyrinthitis Ossificans
- CSF Otorrhoea
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Work-up:
- History: Determine the mechanism of injury, time of onset, and associated symptoms.
- Physical Exam: Complete head/neck examination, look for facial asymmetry, signs of injury (lacerations, hematomas, bruising), assess head/scalp, perform otoscopic examination and tuning fork tests.
- Clinical Facial Nerve Test: Assess temporal, zygomatic, and mandibular branch function.
- House-Brackmann Grading:
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Radiologic Tests:
- HRCT scans to evaluate bony pathology
- MRI to visualize soft tissue
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Facial Nerve Testing:
- Topographic Testing: Assess nerve function of specific branches, help determine the site of injury (e.g., Schirmer's Test, Stapedial Reflex Test, Taste Test, Submandibular Salivary Flow Test)
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Electrodiagnostic Testing: Utilize electrical stimulation to assess nerve conductivity and function.
- Nerve Excitability Test (NET): Compare the amount of current needed for minimal muscle contraction between normal and paralyzed sides.
- Maximal Stimulation Test (MST): Similar to NET but utilize maximal stimulation.
- Electroneuronography (ENoG): Measures electrical activity and degeneration of the nerve.
- Electromyography (EMG): Assesses the activity of the muscle itself.
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Surgical Guidelines:
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General:
- Reconstruction: Can be dynamic (active muscle movement) or static (improve symmetry and reduce complications).
- Informed Consent: Important to inform patients about the potential for asymmetry and lack of normal balance.
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Iatrogenic Injury:
- Transected Nerve: Explore 5-10mm of the involved segment.
- Loss of Function Within 2-3 Hours Post-Surgery: Re-evaluate patient.
- Complete Paralysis Following Temporal Bone Fracture: Immediate surgical exploration, likely nerve transection.
- Partial or Delayed Loss of Function: High-dose steroids, ENoG at 72 hours, potential for exploration.
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Penetrating Trauma:
- Extratemporal: Exploration within 3 days of injury unless injury distal to the lateral canthus.
- Gunshot Wounds: Delayed exploration is recommended.
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General:
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Surgery for Acute Facial Nerve Trauma:
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Facial Nerve Decompression:
- Approach: Transmastoid/Middle cranial fossa approach (intact nerve) or transmastoid/translabyrinthine approach (absent nerve).
- Procedure: Remove bone overlying the nerve, drain hematoma if identified.
- Neurolysis: Cut epineural sheath on either side of the injury point to expose the nerve.
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Facial Nerve Decompression:
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Important Points:
- Thermal Injury: Use diamond burs and copious irrigation during surgery to prevent thermal nerve injury.
- Prognosis: Partial paralysis generally has a better prognosis than total paralysis.
- ENoG Results: >90% degeneration suggests surgical decompression.
Facial Nerve Anatomy and Physiology
- The facial nerve has an intracranial segment, which originates from the brainstem and runs through the internal auditory canal.
- The facial nerve also has intratemporal segments, including:
- Meatal: From the porus acusticus to the meatal foramen.
- Labyrinthine: Fundus to the geniculate ganglion.
- Tympanic: Geniculate ganglion to the second genu.
- Mastoid: Second genu to stylomastoid foramen.
- The facial nerve has extratemporal segments including:
- From the stylomastoid foramen to the pes anserinus.
- Branches into the temporal, zygomatic, buccal, marginal mandibular, and cervical segments.
Facial Nerve Components
- The facial nerve has motor, sensory, and parasympathetic components.
- The motor component supplies the muscles of the facial expression, stylohyoid muscle, posterior belly of digastric, stapedius muscle, and buccinator.
- The sensory component provides taste to the anterior two-thirds of the tongue and sensation to parts of the TM, the wall of the EAC, postauricular skin, and concha.
- The parasympathetic component provides control to the lacrimal gland, seromucinous glands of nasal and oral cavities, and the submandibular and sublingual glands.
Facial Nerve Injury Classification
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Sunderland Nerve Injury Classification: (Class I - V)
- Class I (Neuropraxia): Conduction block, full recovery expected.
- Class II (Axonotmesis): Axon disruption, full recovery expected.
- Class III (Neurotmesis): Disruption of the neural tube, poor prognosis, potential for synkinesis if regeneration occurs.
- Class IV: Epineurium intact, perineurium, endoneurium, and axon disrupted, high risk of synkinesis.
- Class V: Complete disruption, little chance of regeneration, potential for neuroma formation.
Facial Nerve Trauma: Overview
- Second most common cause of facial nerve paralysis after Bell's Palsy.
- Can occur due to temporal bone fractures, accounting for 15% of all facial nerve paralysis cases.
Temporal Bone Fracture
- Makes up 5% of all trauma patients.
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Three types (Ulrich 1926 classification):
- Longitudinal: Most common, fracture line runs parallel to the petrous pyramid.
- Transverse: Fracture line perpendicular to the petrous pyramid.
- Mixed: Combination of longitudinal and transverse fractures.
Testing Facial Function
- Schirmer's Test: Evaluates lacrimal gland function, assessing the amount of tear production.
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Stapedial Reflex: Evaluates the integrity of the facial nerve.
- Sound directed to either ear causes bilateral contraction of the stapedius muscle.
- Diagnostic for cochlear, retrocochlear, brainstem, and facial nerve pathology.
Testing Taste
- Taste Testing: Evaluates the anterior two-thirds of the tongue for sweet, salt, sour, and bitter tastes.
- Electrogustometry: Electrical stimulation of the tongue for taste perception, provides a threshold measurement.
Submandibular Gland Flow
- Sialometry: Measures salivary flow through Wharton's duct using a polythene tube.
Facial Nerve Surgical Guidelines:
- Exploration is recommended for transected nerve during surgery or temporal bone fractures.
- For iatrogenic injury, evaluate the nerve immediately after surgery, wait 2-3 hours for anesthesia to wear off, and then re-evaluate.
- If complete paralysis persists with a known intact nerve, administer steroids and follow up with ENoG to assess degeneration.
- Explore if ENoG shows >90% degeneration.
- For penetrating trauma, explore the nerve within 3 days of injury unless it's distal to the lateral canthus.
- For gunshot wounds, delay exploration to assess the extent of damage before surgery.
Facial Nerve Decompression
- Localize the injury preoperatively.
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Approach:
- Intact nerve: Transmastoid/middle cranial fossa approach.
- Absent nerve: Transmastoid/translabyrinthine approach.
Acute Facial Nerve Trauma
- Neurolysis: Cut the epineural sheath to expose the nerve.
Dynamic and Static Reanimation Surgery
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Dynamic Surgery:
- Regional muscle transfer: Use existing muscles in the head and neck to restore facial movement, such as the temporalis muscle transfer.
- Microneurovascular free muscle transfer: Transfer a muscle from another region, such as the gracilis or latissimus dorsi muscle, to the face.
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Static Reanimation Surgery: Improve facial appearance and function with procedures like:
- Eye: Eyebrow repositioning, eyelid weight, tarsorraphy (eyelid suturing)
- Nose: Static sling procedures for the corner of the mouth, cartilage grafts to widen the nasal cavity.
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Description
This quiz covers the causes, complications, and evaluation methods for facial nerve trauma. Learn about injury mechanisms and necessary examinations, including radiologic tests and functional assessments. Test your knowledge on facial nerve injuries and their implications.
