Management of Truamatic Facial Nerve Paralysis

Dr. Erami M.D.ENT Resident

Department Of ENTShahid Sadoghi Hospital

Yazd Iran

Seven percent of temporal bone fracturesresult in facial paralysis, and 25% of such cases involve complete paralysis

The latency of delay in onset of facial palsyranges from 1 to 16 days

Differentiation of delayed onset fromdelayed diagnosis

delayed diagnosis :paralytic agent and is intubated before the examination of facial functionattention is given to other life-threatening complicationsshould be treated in a manner similar tothe immediate-onset patients

choice of which patients should undergoexploration:

based on prognostic factors for poor outcome

predict the recovery of facial nerve the timing of onset (delayed vs. immediate

onset)

most important of the predictive factors the severity of the injury (penetrating vs.

nonpenetrating) the presence of associated infection

Turner reviewed a large series of traumatic facial paralysis patients who were treated conservatively.

36 immediate-onset ……. 75%34 delayed-onset …… 94%

Complete recovery occurred in 94% of the delayed-onset cases and 75%of immediate-onset cases

Nash and colleaguessimilarly examined conservative management

25 patients with immediate-onset…..<40%20 patients with delayed-onset…..80%

Review of the literature argues strongly against surgical exploration and decompression of delayed posttraumatic facial paralysis

if facial function is present in the emergency department and subsequently deteriorates, our experience is that the patient will recover without surgical treatment.

degree of facial nerve injury:also a critical factor that guides the management algorithm

Incomplete paresis rarely fails to resolve spontaneously

electrodiagnostic test:

evoked electromyography(EEMG)

standard electromyography (EMG)

Hilger facial nerve stimulator

nerve excitability test (NET)the current is increased until the threshold is reached, which is manifested with facial twitching

Maximal stimulation test (MST)the intensity of the stimulus is increased until the amount of facial contraction plateaus or is limited by patient intolerance

In the NETA threshold difference of 3.5 mA or greater between the affected and nonaffected sides of the face suggests signifiant neural degeneration

The test is most useful between 3 days and 14 after injury in patients with dense facial paralysis to differentiate between neurapraxic and degenerative injuries

electrodiagnostic testing cannot reliably differentiate a neurapraxic injury from a laceration of the nerve for up to 3 to 5 days.

The testing is unnecessary in incomplete paralysis, in which recovery is almost always 100%.

EEMG has been popularized by Fisch in a version called electroneuronography, which differs from EEMG only in the useof bipolar stimulating and recording electrodes.

provide similar information to the MST, butin an objective fashion.

The key factor in the decision to surgicallyexplore a facial nerve is whether the nerve is suspected of being severed, crushed, or impaledwith bone fragments

Because it is not possible to differentiate a Sunderland fith-degree injury (severed nerve) from a third- or fourthdegree injury on the basis of electrodiagnostic testing, exploration is warranted only in patients with complete immediate-onset paralysis in whom electrical stimulability is lost

these are the patients at risk for crushed, partially severed, and transected nerves

The site of injury of the facial nerve in temporal bone fractures is in the perigeniculate region in 80% to 93% of patients

a second lesion in the mastoid segment

Fischadvocates a translabyrinthine approach for transverse fracturesand a combined transmastoid/middle cranial fossa approach for longitudinal fractures.

Maydescribed a transmastoid/supralabyrinthine approach to the region of the geniculate ganglion for facial nerve decompression.

The translabyrinthine approach is : advocated for facial nerve exploration in patients

with profound hearing loss The approach provides excellentexposure for

decompression,nerve rerouting with direct reanastomosis,cable grafting

otic capsule–sparing fractures with ossiculardiscontinuity:

transmastoid/supralabyrinthine approach

This approach generally requires dislocation of the incus and ossicular reconstruction at the completion of the operation

If the patient has any:1.contralateral hearing loss or2.if the anatomy is not conducive for supralabyrinthine exposure,a middle cranial fossa approach is used.

Timing of facial nerve repair:advocates exploration when electroneuronographyindicates that 90% degeneration has occurred within 6 days,and he argues that decompression should be performed early to minimize further degeneration

May also advocates :Early exploration; his series demonstrated a correlation of best results with a shorter interval between injury and repair

The range in latency to recovery of facial function variesfrom 1 day to 1 year.

Summary of Facial Nerve Treatment Algorithm

Summary of Facial Nerve Treatment Algorithm

patients with delayed-onset:Unless medically contraindicatedare placed on a 2-week course of systemic corticosteroids and are observed.

Patients with complete paralysis of immediate onset are tested with the Hilger nerve stimulator between days 3 and 7 after injury

Facial nerve injuries that occur in an otic capsule–disruptingfracture are explored via a translabyrinthineapproachOtic capsule–sparing fracturestwo surgical approaches 1.transmastoid/supralabyrinthine 2. transmastoid/middle cranial fossa

transmastoid/supralabyrinthine:In patients with well-aerated mastoid air-cell systems or with ossicular discontinuity

transmastoid/middle cranial fossa :poorly aerated mastoid aircell system or if total facial nerve decompression cannot beachieved via the transmastoid/supralabyrinthine

The transmastoid facial nerve decompression begins with:

complete mastoidectomyskeletonization of the

tegmen mastoideum superiorly,the sigmoid sinus posteriorlyThe posterior EAC wall anteriorly.

The antrum is opened, whichexposes the short process of the incus and the lateral semicircular canal.

The semicircular canals are then skeletonized. The facial recess is opened, and the facial nerve is skeletonized from the second genu to the stylomastoid foramen

The lateral semicircular canal anddigastric ridge are important landmarks for identifiation of the facial nerve.

The tympanic segment of the nerve is immediately inferior to the lateral canal

the anterior margin of the digastric ridge marks the location of the stylomastoid foramen.

The short process of the incus is identifid but should not be disturbed by an instrument or a rotating bur.

The facial recess is opened with a small diamond bur to allow visualization of the tympanic segment of CN VII in the middle ear

Advantages and Usesexcellent exposure of the mastoid and tympanic segments Exposure of the geniculate ganglion requires

removal of the incus, which can be replaced at the end of the operation

The labyrinthine segment cannot be reached unless the ampulla of the superior semicircular canal is sacrified.

Axial-cut high-resolution computed tomography scan demonstrating a transverse-oriented fracture that resulted from a gunshot injury and disrupted the otic capsule. The arrow points to the fracture line.

Axial-cut high-resolution computed tomography scan demonstrating a longitudinally oriented fracture that has spared the otic capsule. Arrows point along the fracture line.

Majority of the patients in our series had longitudinal fracture which was associated with the involvement of the fallopian canal in the perigeniculate region.

Hematoma, multiple bone chips compression, and edemawere the main findings in our patients

The rate of recovery within HBG I-II after total facial nerve exploration in our short series is 70%

Stretch, com-pression injuries with disruption of the endoneurial tubules undetectable at the time of surgery may be associated with suboptimal results in our series

Conclusion: HRCT of temporal bone was able to accurately reveal fracture of fallopian canal at geniculateganglion and labyrinthine segment in the vast majority cases, but severely underestimated fracture at pyramid segment and mastoid segment of fallopian canal