Fisch, U.

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The Journal of Laryngology and OtologyJanuary 1980. Vol. 94. pp. 129-134Management of intratemporal facialnerve injuriesBy U. FISCH, ZurichSKULL fractures involving the temporal bone are, following Bell's palsy,the second most common cause of facial paralysis in adults (17 per centof the cases) and the most common cause of a facial nerve lesion inchildren (30-4 per cent of all cases). In spite of this situation and of recentprogress in the microsurgical repair of intratemporal facial nerve lesions(Fisch, 1979), confusion still exists as to the proper management of afacial palsy resulting from trauma to the temporal bone. We have treated,at the ENT Department of the University of Zurich, 93 patients with facialparalysis secondary to fractures of the petrous bone. It is the purpose ofthis paper to present guidelines that have been proved to be of value.From the clinical point of view, temporal bone fractures are bestdivided into longitudinal and transverse, according to the preservation orloss of inner ear function. Mixed fractures can be disregarded, becausethey have to be considered as longitudinal in cases of intact inner earfunction, and as transverse in cases of total inner ear loss. Twenty per centof the longitudinal and 40 per cent of the transverse fractures are accom-panied by facial palsy. As long as the post-traumatic palsy remainsincomplete, a good prognosis, with total spontaneous return of facialfunction, is assured. However, in cases with complete clinical paralysis,the patient has to be submitted as early as possible to electrical testing, inorder to find out the degree and evolution of degeneration of the motornerve fibers. For this purpose we advocate electroneuronography (ENoG),because this method alone will provide quantitative information on thenumber of degenerated facial nerve fibers (Fisch, 1979). Animal experi-ments have shown that injuries requiring surgical repair will induce the' degeneration of more than 90 per cent of motor nerve fibers within 6 daysof onset of the palsy. In cases of skull fracture, therefore, surgical exposureof the facial nerve is indicated when ENoG demonstrates more than 90 percent degeneration within 6 days of the onset of palsy. It is important to; realise that the same criterion applies to immediate or to delayed palsy.It is true that a palsy with delayed onset generally carries a better prog-nosis than an immediate one, but a delayed palsy leading to more than90 per cent degeneration within 6 days of onset of the palsy (not of thelesion!) may also lead to an irreversible situation.In our hands, the most reliable topodiagnostic test is Schirmer's test(Fig. 1). However, this test should not be used to identify a 'dry eye', but129use, available at https:/www.cambridge.org/core/terms. https://doi.org/10.1017/S0022215100088575Downloaded from https:/www.cambridge.org/core. University of Basel Library, on 11 Jul 2017 at 08:22:21, subject to the Cambridge Core terms of130 PROFESSOR DR. U. FISCHSchirmer's test: abnormal values of tearingUNILATERAL REDUCTIONb-aa + b 700 >30%BILATERAL REDUCTIONa+b < 25 mmFIG. 1Criteria used for the statistical evaluation of Schirmer's test. Note that traumatic rupture ofthe petrosal nerve leads not only to a unilateral reduction in lacrimation, but also to sym-metrically reduced tearing.Typical longitudinal fracture producing facia/para/ysisGREATER SUPERF.PETROSAL NERVEINTERNAL AUDITORYCANALFACIAL NERVESTYLOMASTOIP \lFORAMEN < £ -FIG. 2Schematic representation of longitudinal fracture explaining the high percentage of lesions ofthe Fallopian canal just distal to the geniculate ganglion.use, available at https:/www.cambridge.org/core/terms. https://doi.org/10.1017/S0022215100088575Downloaded from https:/www.cambridge.org/core. University of Basel Library, on 11 Jul 2017 at 08:22:21, subject to the Cambridge Core terms ofMANAGEMENT OF INTRATEMPORAL FACIAL NERVE INJURIES 131it has to be evaluated on a statistical basis. An abnormal degree oflacrimation is present when the secretion is reduced unilaterally by morethan 30 per cent of the total lacrimal secretion, or when the total amountof lacrimation (in spite of symmetry) is less than 25 mm. According to thiscriterion, Schirmer's test was found to be pathological in 93 per cent ofImpingingfragmentof boneIncisedepineuriumCollagensplintAdhesiveIntraneuralhaematomaGreatersup. petrosalnerveSilverclipFIG. 3Most common types of injury found after longitudinal fractures, and their surgical repair.use, available at https:/www.cambridge.org/core/terms. https://doi.org/10.1017/S0022215100088575Downloaded from https:/www.cambridge.org/core. University of Basel Library, on 11 Jul 2017 at 08:22:21, subject to the Cambridge Core terms of132 PROFESSOR DR. U. FISCHpatients complying with the above-mentioned indications for surgery.This means that, in order to deal properly with facial nerve injuries due toskull fractures, one has to have a perfect knowledge of the otoneuro-surgical procedure.The high incidence of proximal lesions requiring the middle cranialfossa approach in longitudinal fractures is due to the fact that suchfractures usually begin in the temporal squama, extending then across theroof of the middle ear, close to the labyrinthine capsule, and ending in themiddle cranial fossa near the carotid canal. Therefore, the Fallopian canalis usually injured (Fig. 2) just distal to the geniculate ganglion. The mostcommon types of lesion that we have observed after longitudinal fracturesof the temporal bone are the following:(a) impression of a bony fragment within the Fallopian canal (20 percent)(b) complete section of the facial nerve distal to the genu (30 per cent)(c) intraneural hematoma at the level of the genu (50 per cent).The surgical repair of the above-mentioned lesions consists (Fig. 3) of:(a) removal of the impinging fragment of bone, with incision of theepineurium of the nerve(b) re-routing of the Fallopian canal along the superior ampulla, withTypical transverse fracture producing facia/paralysis/ \ \/ \ \/ N \T / ^A, A2FIG. 4Schematic representation of a transverse fracture, indicating why the facial nerve is usuallyinjured in two places.use, available at https:/www.cambridge.org/core/terms. https://doi.org/10.1017/S0022215100088575Downloaded from https:/www.cambridge.org/core. University of Basel Library, on 11 Jul 2017 at 08:22:21, subject to the Cambridge Core terms ofMANAGEMENT OF INTRATEMPORAL FACIAL NERVE INJURIES 133excision of the genu and end-to-end anastomosis (or nervegrafting)(c) evacuation of the intraneural hematoma, with incision of theepineurium and clipping of the greater petrosal nerve.Clipping of the greater petrosal nerve is important, in order to avoid themisdirection of regrowing motor nerve fibers (Fisch, 1979).Transverse fractures of the pyramid usually extend through thelabyrinthine capsule of the temporal bone and, in 70 per cent of cases,they produce a double lesion situated in the proximal labyrinthine segmentof the Fallopian canal as well as in its tympanic segment (Fig. 4). Thehigh incidence of a double facial nerve injury requires total exposure of theintratemporal course of the facial nerve, through the translabyrinthineapproach, even when a lesion has been seen after exposure of the middleear. In our hands, what we have called the meato-mastoidal re-routing ofthe Fallopian canal (Fisch, 1973) is the best method of repair of a facialnerve lesion after transverse fracture of the temporal bone (Fig. 5).Before proceeding to an end-to-end anastomosis or to a nerve graftingprocedure, a frozen section of the proximal stump of the facial nerveSTYLOMASTOIDFORAMEN MEATALFORAMENPOROUSACOUSTICUSINTERNUSBFIG. 5The meato-mastoidal re-routing of the facial nerve performed through the translabyrinthineapproach is the most successful repair of a facial nerve injury after transverse fracture10use, available at https:/www.cambridge.org/core/terms. https://doi.org/10.1017/S0022215100088575Downloaded from https:/www.cambridge.org/core. University of Basel Library, on 11 Jul 2017 at 08:22:21, subject to the Cambridge Core terms of134 PROFESSOR DR. U. FISCHshould be studied. If complete fibrosis of the meatal and intracranialsegments of the facial nerve has resulted from rupture of the correspondingnutritional vessels, a hypoglossal-facial nerve cross-over is performed.When is the best time to carry out early surgery? In the presence ofan immediate facial paralysis which reaches more than 90 per cent de-generation within 6 days, a delay of 3-4 weeks has given the best results.Conversely, a delayed palsy reaching more than 90 per cent degenerationwithin 6 days should be operated on immediately, in order to evacuate anyintraneural hematoma and to avoid the formation of intraneural fibrosis.Delayed surgery is indicated if no return or insufficient return of facialfunction occurs within 6 to 12 months following the injury.The 2-year follow-up analysis of results has shown that grafting orend-to-end anastomosis of the facial nerve following skull trauma willlead to 60 per cent return of facial movements on average. Evacuation ofan intraneural hematoma or removal of an impinging fragment of bone inthe Fallopian canal is followed, on average, by an 85 per cent return offacial movements.REFERENCESFISCH, U. (1973) Operations on the facial nerve in its labyrinthine and meatal course. In:Surgery of the Facial Nerve. Ed. A. Miehlke.FISCH, U. (1979) Facial paralysis. In: Clinical Laryngology. Ed. Maran and Stell, BlackwellScientific Publications, Oxford-London-Edinburgh, Melbourne.use, available at https:/www.cambridge.org/core/terms. https://doi.org/10.1017/S0022215100088575Downloaded from https:/www.cambridge.org/core. University of Basel Library, on 11 Jul 2017 at 08:22:21, subject to the Cambridge Core terms of

Management of intratemporal facial nerve injuries

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