the facial nerve current trends in diagnosis, treatment, and rehabilitation

8/13/2019 The FACIAL NERVE Current Trends in Diagnosis, Treatment, And Rehabilitation

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OTOLARYNGOLOGY FOR THE INTERNIST 0025-7125/99 8.00 + .OO

THE FACIAL NERVECurrent Trends in Diagnosis, Treatment,and Rehabilitation

C. Gary Jackson, MD, FACS, and Peter G . von Doersten, MD

Facial paralysis is a potentially devastating disorder. Few impairments havea more negative effect on socioeconomic capacity in an individual's life. Thefacial nerve is responsible for facial expression, lacrimation, salivation, taste, andsensation. It is also the most commonly paralyzed nerve of the body. Paralysismay result from infection, tumor growth, trauma, and several other causes. Thenerve is further susceptible to spasm from compression by nearby intracranialvessels or tumors. It has a tortuous bony course longer than any other nervethrough the densest bone in the body, making surgery on it quite difficult. Ithas a fragile blood supply. Finally, the facial nerve is difficult to treat, rehabilitate,and reanimate functionally. Advances in microbiology, radiographic imaging,electrodiagnostic testing, and microsurgery have provided great insight into thepathophysiology, diagnosis, treatment, and rehabilitation of the facial nerve. Themost important tenet for all physicians in treating facial nerve pathology isproper diagnosis and early treatment. The terms Bell's p l s y and i d i o p t h i c f c i lp r l y s i s may no longer be considered synonymous. DNA polymerase chainreaction (PCR) testing on the endoneurial fluid of the facial nerve in patientswith sudden ipsilateral facial paralysis has supported the herpes simplex virus(HSV) as the causative agent in paralysis previously considered idi~pathic'~,or secondary to immunologic or vascular proce~ses.'~A differential diagnosis(to be discussed later) must always be considered because easily diagnosedentities, such as otitis media or parotid neoplasms, should not be overlooked.Early treatment of facial nerve pathology is imperative because paresis treatmentwithin 72 hours can have implications on return of function in terms of bothtime and degree.sThis article focuses on the evaluation, differential diagnosis, medical treat-

From The Otology Group, Nashville, Tennessee (CGJ); and Rocky Mountain Eye and EarCenter, PC, Missoula, Montana (PGV)

MEDICAL CLINICS OF NORTH AMERICAVOLUME 83 * NUMBER 1 * J A N U A R Y 1999 179


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18 JACKSON & VON DOERSTEN

ment, and rehabilitation of facial nerve pathology, with primary emphasis onfacial paralysis. Surgical management is also discussed, including reanimationof the paralyzed face.

FACIAL NERVE ANATOMY AND HISTOPATHOLOGYA brief synopsis of facial nerve anatomy is crucial in understanding itspathophysiology (Fig. 1).The facial nerve is a mixed nerve with special visceralefferent (facial musculature), general visceral efferent (parasympathetic lacrimal,minor, submandibular, sublingual gland innervation), special visceral afferent(taste, anterior two thirds of tongue), and general somatic afferent (cutaneousinnervation of external auditory canal and pinna) functions. It originates from

the pontomedullary junction of the brain stem and courses laterally to theinternal auditory canal (IAC), which it enters with the cochleovestibular nerve.A thin myelin sheath encompasses the nerve in its intracranial portion. It issubject to demyelinization from vessel loop pressure with resultant ectopic nervestimulation.66,7 The intracranial portion of the nerve is able to withstand slowstretching from a tumor but is quite susceptible to trauma. As the nerve travelsfarther laterally in the IAC, it enters the narrow fallopian canal, becomingencased in periosteum and epineurium. This canal measures roughly 30 to 33mm in length96 nd consists of three portions-the labyrinthine, tympanic, andmastoid. Of significance, the narrowest portion is at the labyrinthine section,which contains the geniculate ganglion. This section averages 0.68 mm in diame-terZR he facial nerve occupies 83% of the available space compared with 23%in the mastoid It is the labyrinthine portion where it is most likely

ganglion

etrosal n

Sensory and motorroots of VII Geniculate Ptervqopalatine

Stapedius n

Parotid qx Submandibular.gland and ganglion

Musclesof Expression

Figure 1. Facial nerve anatomy and histopathology.


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THE FACIAL NERVE 181

that a vicious cycle of edema from infection, vascular compromise, and ischemia,thought to be the pathophysiologic process in Bell's palsy, can occur.Four branches of the facial nerve occur within the fallopian canal-thegreater and lesser superficial petrosal nerves, the nerve to the stapedius muscle,and the chorda tympani nerve. Topognostic testing for facial nerve dysfunctionincludes examining tearing, salivation, stapedial reflexes, and taste, attributableto the functions of each of these branches. Today, topognostic testing is of littleclinical utility.The facial nerve exits the stylomastoid foramen of the skull base; gives offbranches to the posterior auricular muscles and the posterior belly of the digas-tric; then proceeds anteriorly into the parotid gland, where it divides at the pesanserinus into the temporal, zygomatic, buccal, marginal mandibular, and cervi-cal branches. These nerves are responsible for facial expression, eye closure, andassistance with mastication and speech.The facial nerve derives both an intrinsic and an extrinsic blood supply, theformer derived from the latter.I2The extrinsic vascular supply comes from threeprimary sources-the stylomastoid artery, the petrosal artery, and the internalauditory (labyrinthine) artery-and derives the intrinsic The narrowlabyrinthine portion of the nerve is a transition watershed zone between bloodsupply from the vertebral and carotid artery This vasculature coursesbetween the epineurium and the bony periosteum and is jeopardized by trauma,swelling from infection, and surgical injury. During these times, survival of thenerve depends on the tenuous supply of the intrinsic system.

NERVE INJURY STAGESThe stages of nerve injury were well described by Seddon in 1943Rh ndSunderland in 197893 nd correspond with a spontaneous facial recovery gradingscale proposed by House and Brackmann in 1985 (Table l . , O The degrees ofinjury range from 1 to 5 and correspond with neurapraxia, axonotmesis, neu-rotmesis, partial transection, and complete transection. Neurapraxiu is a reversible

block of conduction caused by an increase in intraneural pressure, with resultantfocal demyelinization and axoplasmal damming. Recovery of the nerve is oftencomplete to a House-Brackmann grade 1 level. Axonotmesis is a more permanentcompression with axoplasmal flow interruption and distal wallerian degenera-tion with partial loss of axons, often recovering to a partial facial weakness orHouse-Brackmann grade 2. Neurotmesis relates to the permanent loss of axonaland myelin tubes. Facial recovery may improve to a moderate-to-severe weak-ness of the face, or House-Brackmann grade 3 4 . Faulty regeneration of the nervemay also lead to facial synkinesis or contracture. Partial or complete transection ofthe nerve may lead ultimately to either minimal perceptible facial function(House-Brackmann grade 5) or no function (House-Brackmann grade 6).Gantz et aP0 have used intraoperative evoked electromyography testing todetermine the site of lesion in Bell's palsy during operative decompression ofthe nerve. These surgeons were able to stimulate the facial nerve distal to thegeniculate ganglion but not proximal, supporting the theory of a neurapraxicnerve at its labyrinthine portion. Magnetic resonance (MR) imaging has alsoshown significant enhancement with gadolinium in the labyrinthine region inpatients with Bell's palsy, supporting this as the affected site. , R5 Jackson et a147confirmed this histologically.


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Table 1. HOUSE-BRACKMANN CLASSIFICATION OF FACIAL FUNCTIONGrade Characteristics

111 Moderatedysfunction

V. Severedysfunction

I. Normal Normal facial function in all areas11. Mild dysfunction GrossSlight weakness noticeable on close inspectionMay have slight synkinesis. At rest, normal symmetry andtoneMotionForehead: moderate-to-good functionEye complete closure with minimal effortMouth slight asymmetryObvious, but not disfiguring difference between the twoGrosssides. Noticeable but not severe synkinesis, contracture, orhemifacial spasmAt rest, normal symmetry and toneForehead: slight-to-moderate movementEye: complete closure with effortMouth: slightly weak with maximum effortObvious weakness and/or disfiguring asymmetry. At rest,

Motion

IV. Moderately severe Grossdysfunction normal symmetry and toneMotionForehead: noneEye: incomplete closureMouth: asymmetric with maximum effortOnly barely perceptible motion. At rest, asymmetryForehead: noneEye: incomplete closureMouth slight movement

GrossMotion

VI. Total paralysis No movementFrom House W, Brackmann D Facial nerve grading system. Otolaryngol Head Neck Surg 93146-147,1985.

DIAGNOSISThe examination of the patient with facial paralysis has three main objec-tives: to identify 1) the site of the lesion, (2) the degree of dysfunction, and, ifpossible, (3) the cause.

History and Physical ExaminationA s with all disease, the history and physical examination are of paramountimportance in facial paralysis. The history should detail date of onset, rapidityof onset, associated symptoms, and associated systemic diseases to help deter-mine a traumatic, neoplastic, or infectious cause. (Metabolic, neurologic, toxic,iatrogenic, and systemic causes may also be considered.) The physical examina-tion should include a careful head and neck examination, with careful attentionto the ear, parotid gland, other cranial nerves, salivation, tearing, and taste.Tuning forks can crudely assess hearing. Grading paralysis according to the

House-Brackmann grading system is helpful, with measurements of range of


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motion of the eyebrows and a quantification of ability to close the eye and tolateralize the oral commissure. A complete audiogram with stapedial reflextesting is helpful in determining eighth cranial nerve function (a unilateralsensorineural hearing loss would raise suspicion for an acoustic or facial neu-roma), stapedius muscle function (part of topognostic testing to identify siteof lesion), and presence of a conductive loss (raising suspicion for middleear disease).

Radiologic ImagingIf a parotid mass is palpated or suspicion is aroused for a compressive

lesion in the cerebellopontine angle or internal auditory canal, imaging may beobtained. A computed tomography (CT) or MR imaging scan (with fine needleaspiration for specimen diagnosis) may be used for the parotid gland. The bestintracranial facial nerve examination is with a gadolinium-enhanced MR im-aging scan. As stated earlier, the geniculate ganglion within the labyrinthinefacial nerve enhances in Bells palsy. Acoustic neuromas, meningiomas, hemangi-omas, and other cerebellopontine angle (CPA) lesions may be diagnosed withthis technique. A less expensive test for examining the brain stem, CPA, andIAC is the limited T2-weighted MR imaging scan without contrast using a spin-echo technique. Some intracranial masses may be missed with this test, however.A high-resolution CT scan is useful for examining the course of the facial nervewithin the temporal bone, particularly after trauma.

Electrical TestingAlthough the initial physical examination documents the severity of theparalysis, it does not reveal the neurophysiologic status of the facial nerveitself, the progression of disease, the prognosis, or the indication for further

intervention, including surgical decompression. Electrodiagnostic testing hasbeen used in selecting patients for treatment and in predicting o ~ tc o m e .~ * ~h 83The most commonly used electrical tests include the minimal nerve excitabilitytest, the maximal stimulation test (MST), and electroneuronography (ENOG).These tests rely on percutaneous stimulation of the facial nerve and d o notshow abnormalities until 72 hours after nerve degeneration. Quantitative ratingsystems have been applied to both MST and ENOG, and each has been used toevaluate the facial nerve after paralysis. Opinions differ on the accuracy of eachmodality, but MST testing is fairly easy to perform and inexpensive, requiringonly a Hilger nerve stimulator (WR Medical Electronics Co., Stillwater, MI). Apoint score is awarded for stimulation of various branches of the facial nerve,and the score is used to predict outcome.83ENOG testing records a compoundaction potential (CAP) and latency after stimulating the facial nerve, and thepercent degeneration of the amplitude of the CAP compared to the control sideof the face is used to predict outcome. Several authors have advocated surgicaldecompression of the facial nerve based on a CAP degeneration of 90% orgreater in Bells palsy because of a poor prognosis without surgical inter-~ e n t i o n . ~ ~ ,7 A poor prognosis has not been determined for traumatic paralysiswith CAP degeneration of 90% or greater.89


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184 JACKSON & VON DOERSTENF CI L NERVE P THOLOGYFacial Paralysis

Perhaps the most complete differential diagnosis of facial palsy has beencompiled by May and Klein (Table 2).62These authors divide causes into severallarge categories: birth, trauma, neurologic, infection, metabolic, neoplastic, toxic,iatrogenic, and idiopathic. A complete discussion of each of these entities isbeyond the scope of this article. Several areas of interest over the past severalyears have been the association of facial paralysis with Lyme disease,'*, 6 humanimmunodeficiency virus (HIV),53,2 human T-lymphotropic virus type I (HTLV-1),48and HSV.69,0, 8 A careful history at the time of presentation includesquestioning regarding exposure to tick bites and risk factors for HIV. Withregards to HSV, perhaps no other topic has elicited more controversy within theotologic community regarding the facial nerve in the past 20 years.

Infectious CausesBell's Palsy

Bell's palsy is a lower motor neuron, ipsilateral facial paresis, which is acutein onset, is frequently preceded by a viral prodrome, and is generally regardedas polyneuropathic. Affecting roughly 20 people per 100,000 per year? 35, 69 it isequally distributed between the sexes and sides of the face. The risk to pregnantwomen is 3.3 times greater than that for nonpregnant women.37 The risk ofrecurrence is lo , and this recurrence may occur on either side. Of those whoexperience recurrence three times, the risk of a fourth recurrence is 5Oy0.~'Diabetics are at higher risk6 (4.5 times more likely), and the risk of Bell's palsyincreases with each decade of life.35Both AdourZ and May and Kleidz describe a prodromal illness before theonset of Bell's palsy (60% of patients), with frequent associated facial numbness,epiphora, pain, dysgeusia, hyperacusis, and decreased tearing (50%). Familialtendencies are implicated in 14 of cases, and a majority (900/,)of patients havea decreased or absent stapedial reflex.Adour and May and Klein disagree on calling Bell's palsy a diagnosis ofexclusion. Adour et a14 advocate making the diagnosis based on the history andclinical symptoms and the presence of dysgeusia and hyperacusis. May andKlei@ recommend excluding other diagnostic entities based on a definedworkup and a lengthy differential diagnosis. Other authors have also describedBell's palsy as a diagnosis of and have frequently used the termidiopathic. With the discoveries using PCR DNA testing, the use of this term hasbeen further questioned. Consideration of the cause as an HSV-mediated viralinflammatory immune mechanism has become more widely accepted.I3,The treatment of Bell's palsy has become less controversial and involvesboth medical and surgical options. In 1972, Adour' published a large controlledstudy on the treatment of Bell's palsy with corticosteroids, showing an 89%complete functional recovery in 194 patients treated with steroids comparedwith a 64% complete recovery in control patients. Despite some criticism of thestudy and other studies9, 4 that corroborated Adour's findings, steroid use forBell's palsy is widespread today.87,2Because a viral cause has long been postulated, a study reviewed the useof antiviral agents5 in the treatment of Bell's palsy. In a randomized, double-

84


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Table 2. CAUSES OF FACIAL PALSY IDENTIFIED IN A REVIEW OF MEDICALLITERATURE 1900-1 990Birth

MoldingForceps deliveryDystrophia myotonicaMobius syndrome (facial diplegia associatedwith other cranial nerve deficits)TraumaBasal skull fractures

Facial injuriesPenetrating injury to middle earAltitude paralysis (barotrauma)Scuba diving (barotrauma)Lightning

NeurologicOpercular syndrome (cortical lesion in facialmotor area)Millard-Gubler syndrome (abducens palsywith contralateral hemiplegia caused by

lesion in base of pons involvingcorticospinal tract)InfectionExternal otitisOtitis media

MastoiditisChickenpoxHerpes zoster cephalicus (Ramsey Hunt

syndrome)EncephalitisPoliomyelitis (type I)MumpsMononucleosisLeprosyInfluenzaCoxsackievirusMalariaSyphilisScleromaTuberculosisBotulismAcute hemorrhagic conjunctivitis (enterovimsGnathostomiasisMucormycosisLvme disease

70

Cat scratchAIDSMetabolicDiabetes mellitusHyperthyroidismPregnancyHypertension

Acute porphyriaVitamin A deficiencyBenign lesions of parotidCholesteatomaSeventh nerve tumor

Neoplastic

Glomus jugulare tumorLeukemiaMeningiomaHemangioblastomaSarcomaCarcinoma (invading or metastatic)Anomalous sigmoid sinusCarotid artery aneurysmHemangioma of tympanumHydradenoma (external canal)Facial nerve tumor (cylindroma)SchwannomaTeratomaHand-Schuller-Christian diseaseFibrous dysplasiaNeurofibromatosis I1Thalidomide (Miehlke syndrome, cranialnerves VI and VII with congenitalmalformed external ears and deafness)

Toxic

Ethylene glycolAlcoholismArsenic intoxicationTetanusDiphtheriaCarbon monoxideMandibular block anesthesiaAntitetanus serumVaccine treatment for rabiesPostimmunizationParotid surgeryMastoid surgeryPosttonsillectomy and adenoidectomyIontophoresis (local anesthesia)EmbolizationDental

IdiopathicBells, familialMelkersson-Rosenthal syndrome (recurrentalternating facial palsy, furrowed tongue,faciolabial edema)

Hereditary hypertrophic neuropathy (Charcot-Marie-Tooth disease, Dkjkrine-Sottas disease)Autoimmune syndromeAmyloidosisTemporal arteritisThrombotic thrombocytopenic purpuraPeriarteritis nodosaLandry-Guillain-Barre syndrome (ascendingMultiple sclerosisMyasthenia gravisSarcoidosis (Heerfordt syndrome-uveoparotidOsteopetrosis

Iatrogenic

paralysis)

fever)

Adnptedfrom May M, Klein S: Differential diagnosis of facial nerve palsy. Otolaryngol Clin North Am 24613444,1991.


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blinded, controlled study, patients treated with prednisone and acyclovir werefound to have a statistically significant faster time to recovery and more completerecovery than patients treated with prednisone alone. The treatment groupreceived 60 mg prednisone per day for 4 days, tapering over a total of 10 days,with 400 mg acyclovir taken five times per day for 10 days. With the advent ofnew antivirals with better gastric absorption (famciclovir and valacyclovir),better uptake is now possible without as great a potential side effect of gastricupset.Surgical decompression for Bell's palsy is advocated only in patients whohave had an ENOG that demonstrates a CAP amplitude decrease of greater than90% and who are in a time window roughly 2 to 3 weeks after the onset ofparalysis.*' The surgical procedure typically involves a middle fossa craniotomyfor decompression of the labyrinthine portion of the nerve and is not recom-mended for patients in poor health or older than age 60. Contraindications areinfection within the middle ear or mastoid or the presence of an only hearingear (because of the risk of iatrogenic hearing loss). Patients with multiple recur-rences of paralysis are also considered candidate^.^^Expected time of recovery of function ranges from weeks to 12 months. Inpatients who have partial paralysis (neurapraxia), approximately 94 recoverfull function within months.79The absence of recovery by 4 months indicates alikely poor outcome with either no return of function or severe synkinesis andcontracture. Unsatisfactory results occur in between 15% and 40 of untreatedpatients.',57.9 Adour et a15 report that patients treated with acyclovir and predni-sone have one half the incidence of synkinesis and facial contracture comparedwith patients treated with prednisone alone.Esslen,z4 in data generated by natural history ENOG and that correlate wellwith the clinical landmark study of Peiter~en?~etermined that in 93% of Bell'spalsy patients, the progression of degeneration is ended by day 10. Return offunction, even if minimal, always occurs within 6 months.79 t is most importantto identify areas of a patient's clinical presentation that suggest a diagnosis otherthan Bell's palsy:

Slowly progressive facial paralysis beyond 3 weeks or no return of functionSimultaneous bilateral facial paralysis excludes Bell's palsy as a diagnosis.Intact forehead movement is seen in 5 of Bell's palsy patients and does notRecurrent unilateral paralysis is consistent with Bell's palsy but is frequentlyPain is not viewed as prognostically or diagnostically significant.Facial hyperkinesis is troublesome because it is seen in vascular compression

Clinical awareness of these major features helps to avoid misdiagnosis or de-layed diagnosis.

within 6 months suggests neoplasm.

necessarily suggest an upper motor neuron lesion.(30 )seen in tumor patients. It is a cause for concern.

and neoplasia.

Herpes Zoster Oticus (Ramsay Hunt Syndrome)In 1907, Ramsay HunP generated his classic description of a syndromecharacterized by facial paralysis, herpetiform vesicular eruptions, and vestibu-locochlear dysfunction. In contrast to Bell's palsy, the viral cause of RamsayHunt syndrome is not disputed. Vesicular eruptions may occur over the ear,face, and neck down to the shoulder. There is more pain than in Bell's palsy, a


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greater likelihood of hearing loss, and a lower incidence of a complete recoveryfrom facial paralysis (54 ).'j8A complete recovery of hearing loss occurs inroughly 45 of patients. Younger patients have a better prognosis.68Treatment for Ramsay Hunt syndrome is similar to that of Bell's palsy.Steroids have been advocated at 1 mg/kg/d in divided doses tapering over 10days.76Further, Dickens et alZ1have found that the initiation of intravenousacyclovir within 72 hours of onset has greatly mitigated the neurologic sequelaeof Ramsay Hunt syndrome. These authors found earlier facial nerve recoveryand return of hearing.

Lyme DiseaseLyme disease is a tick-borne spirochete (Borrelia burgdorferi) infection knownto cause erythema chronicum migrans, meningopolyneuritis, myocardial con-duction abnormalities, and Lyme arthritis. Initially associated with tick bites inthe northeastern United States, the disease is now recognized across NorthAmerica and Europe. Clark et alzohave reported the incidence of facial palsy atgreater than 10 in all patients with Lyme disease, with bilaterality in 25% ofthese. Symptoms after a tick bite (with associated maculopapular rash withcentral clearing) include headache, malaise, myalgias, chills and fever, nauseaand vomiting, and neurologic sequelae. If Lyme disease is suspect, an enzymeimmunoassay may be obtained.90 The treatment of choice is doxycycline ortetracycline, with penicillin and erythromycin as alternatives. The prognosis forreturn of facial function is excellent.20

Facial Paralysis from Bacterial InfectionFacial paralysis may occur from an acute bacterial infection of the middleear or mastoid, chronic otitis media, or necrotizing otitis externa. In 1982, Pollockand Browns2 eported the incidence of facial paralysis in 1250 patients with otitismedia at 0.16% compared with 2% in the preantibiotic era. The route of infectionis thought to be via the bony dehiscences of the fallopian canal, with resultantedema and vascular c~mprornise.~~hronic infection is thought to cause com-pression of the facial nerve from intrafallopian abscesses, granulation tissue, andedema.'j5Cholesteatoma should be suspected if the onset of paralysis is gradual.This is contrasted to the 2- to 3-day onset of paralysis in acute otitis media. Inimmunocompromised hosts with otitis externa, a necrotizing chronic infection(typically from Pseudomonas aeruginosa) can occur, which spreads via vascularand fascia1 planes to cause cellulitis of the skull base and facial paralysis.In cases of acute paralysis with otitis media, treatment consists of intrave-nous antibiotics and surgical myringotomy.20, If paralysis persists more than 2weeks or if fever persists more than 48 hours, a mastoidectomy with facial nervedecompression is advocated.= For chronic otitis media and cholesteatoma, amastoidectomy is also indicated. In cases of malignant (necrotizing) otitis ex-terna, facial paralysis is an ominous sign. Occurring in 38 of patients, facialparalysis is typically predictive of poor patient survival.5'j Treatment is largelymedical, with intravenous antibiotics and occasionally hyperbaric oxygen. Theprognosis is not affected by surgery (other than debridement of granulationtissue in the external canal), and if the patient survives, the chance of facialnerve recovery is roughly


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188 JACKSON VON DOERSTEN

Noninfectious CausesTrauma

Intratemporal facial paralysis may be of a catastrophic origin (head trauma)or may be iatrogenic in nature. In head trauma, the facial nerve is the mostcommonly injured cranial nerve, with temporal bone fractures as the likelycause. One study reports 70 documented temporal bone fractures of 5000 casesof head trauma, 27 of which developed facial nerve paralysis.I6Facial paralysissecondary to surgery of the middle ear and mastoid ranges in incidence fromTemporal bone fractures are typically described in terms of the relationshipof the fracture line to the long axis of the petrous pyramid. Longitudinalfractures are most common and constitute 90% of Injury commonly

occurs to the facial nerve in the region of the geniculate ganglion. Transversefractures are less common but result in 38% to 50% of cases of facialThese fractures tend to transect the IAC through which the facial nerve courses.Many fractures do not fall into the classic definitions of longitudinal or trans-verse and are, in fact, mixed fractures or comminuted fractures.Indications for exploration and repair are fairly well defined, and in contrastto paralysis for infectious causes, no controversy exists regarding the cause.According to May and Sha mba ~gh ;~f there is firm evidence after head traumathat the nerve has been transected, including a sudden onset of complete paraly-sis, loss of electrical activity by ENOG or MST testing by the fifth day, andevidence of a displaced fracture involving the fallopian canal, surgical explora-tion and decompression are warranted. Depending on the site of the lesion,decompression typically entails a middle cranial fossa approach and mastoidec-tomy.For iatrogenic injuries, reexploration is warranted if other causes, such aslocal anesthesia or compression from packing, have been excluded. If the paraly-sis is complete and was noted immediately after surgery (i.e., not delayed inonset), surgicai exploration should be considered. Repairs typically consist ofdecompressing the nerve proximal and distal to the site of injury; opening thenerve sheath to prevent compression from edema; and, if necessary, performinga microneurorraphy (for injury


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attention to the IAC. This examination may require supplementation with a CTscan to examine the bony course of the fallopian canal. For primary tumors ofthe facial nerve with paralysis, recommended treatment is surgical resectionwith end-to-end anastomosis or interposition nerve grafting.44

Melkersson-Rosenthal SyndromeCharacterized by facial paralysis, episodic facial swelling, and a fissuredtongue (scrota1 tongue or lingua plicata), Melkersson-Rosenthal syndrome-associated paralysis typically begtns in adolescence and has been described asboth sporadic and familial.s5 The cause is unknown. With each episode ofparalysis, facial edema worsens, and progressive disfigurement may occur.52Because of the relatively low incidence of this disorder, optimal therapy isdifficult to deduce statistically. Steroid use has been employed as in Bell'spalsy, and some groups have advocated surgical decompression to avoid thedenervation associated with recurrent episodes of paralysis.32,

PARALYSIS IN CHILDRENThe causes for facial paralysis in children are somewhat different than those

for adults. May et a160 have found that Bell's palsy represents the most commoncause (42 of cases), followed by trauma (21%), infection (Is ), ongenitalcauses (8 ), and neoplasm (2%). Identifiable causes are found in between 58%and 72% of cases,7 and are treated based on the cause.In newborns, it is most important to determine whether the paralysis isacquired through trauma or is congenital in nature, so that appropriate therapymay be provided. Smith et aP' have found that of 95 patients with neonatalfacial paralysis, 78% were the result of intrauterine or birth trauma, and the restwere congenital. With trauma, a crush injury is typically suspect in forcepsdelivery, although pressure on the ipsilateral face from the sacrum or in uteromolding during delivery are also suspect.s1A complete return of facial functionwithout sequelae has been found in 91 of cases.9' The facial nerve has beenshown to be vulnerable in the neonate because of the lateral position of thestylomastoid foramen, placing the nerve in a superficial position at its exit fromthe skull base.Facial paralysis in the neonate in congenital malformations has a poorprognosis for recovery. With congenital paralysis, there is an absence of obviousphysical or radiographic findings for trauma, although associated craniofacialabnormalities, particularly of the first and second branchial arch, may occur.6oOf the associated syndromes, perhaps the most commonly addressed is Mobius'syndrome, with a characteristic bilateral facial and abducens palsy and associ-ated extremity abnormalities. Suspect is intrauterine brain stem necrosis42ornuclear agenesis secondary to anomalous brain stem vessel development in thesixth week of gestation.lg A translocation on chromosome 1 has also beeni m p l i ~a t e d . ~~halidomide embryopathy has similar facial findings with limbdefects. Other syndromes associated with neonatal paralysis include Gold-enhar s syndrome; neurofibromatosis; Paland syndrome; cardiofacial anomaly(isolated mandibular branch palsy with cardiac defects); and several bone disor-ders, including McCune-Albright syndrome and os teope tr~sis .~~


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FACIAL HYPERK INESIAThe most common forms of facial hyperkinesia are essential blepharospasm

and hemifacial spasm. Blepharospasm is a bilateral asynchronous firing of theorbicularis oculi muscle (with frequent brow involvement), which may havecoexisting movement of the lower face, mouth, tongue, and neck (Meigessyndrome). The cause is unclear but an extrapyramidal disorder isTreatment consists initially of the injection of botulinum toxin (Botox) into theaffected mu~culature.~~f this treatment is not effective or if complications0ccur,2~ partial or complete surgical myectomy is adv0~ated.I~Hemifacial spasm is a vascular compressidn syndrome and can be differenti-ated from essential blepharospasm by its synchronous muscle twitches, lack ofdisappearance in sleep, degree of spasticity (more complete and longer lasting),unilaterality, cause (vascular compression at the nerve root entry zone), andtreatment.zzThe condition is rare, with a prevalence of 7.4 men per 100,000, and14.5 women per 100,000 in the white population of the United States.* Multiplecauses have been suggested, but evidence based on electrophysiologic data andsurgical observation suggests compression at the nerve root entry zone, mostcommonly by the posterior-inferior cerebellar artery.22, 49 The kindling theorypostulates that vessel compression causes demyelinization, resulting in an ec-topic focus of excitation of the nerve.66Treatment is typically with an initial trial of botulinum toxin, with subse-quent injections every 4 to 6 months. More definitive treatment is with microvas-cular decompression of the facial nerve via a retrosigmoid craniotomy. In areview of the literature, Illingworth et a1 report that in microvascular decompres-sion surgery, 62% to 97% of patients had complete resolution of spasm, 1.3% to25% had partial relief, and 1.3% to 15% had no relief in the large studiesp e r f ~ r m e d . ~ ~n their own series, these authors patients had a 92% free-of-spasmrate at a mean follow-up of 8 years.

REHABILITATIONWith facial paralysis, either temporary or permanent, great attention is paidto protection of the eye. Major factors affecting the eye are lagophthalmos,paralytic ectropion of the lower lid, concomitant trigeminal nerve loss, anddecreased tear produ~tion.~~fter paralysis, it is imperative to provide thepatient with artificial tears and ophthalmic ointments. Glasses or goggles areimportant in protection from light, wind, and dust. Protection of the eye at night

is frequently required and requires proper technique.Long-term treatment for paralysis may include tarsorrhaphy, lateral can-thoplasty, and gold weight implant to the upper lid. Ophthalmologic consulta-tion is indicated. Priorities of rehabilitation are corneal protection, comfort,preservation of vision, improved function, and esthetic r e s t ~ ra t i on .~ ~Restoration of function to the face is possible with several techniques. Aftera traumatic injury to the nerve, a microsurgical reanastomosis or nerve graftingis possible. Grafting donor sites include the sural, great auricular, and medianantebrachial cutaneous nerves. For Bells palsy, a wait of 12 months is advocatedto monitor for spontaneous return of function before surgical i n t e r~ e n t io n .~ ~Electromyography may be helpful in assessing early return. If no return ispresent, nerve substitution is possible in the form of a hypoglossal-to-facialnerve crossover. This procedure preserves muscle tone should other techniquesbe in consideration. Attention has been paid to the cross-facial nerve grafting


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technique, which is most successful when performed early after injury3* Forpatients in whom facial paralysis is long-standing with either congenital paraly-sis or fibrosis of the musculature, regional muscle transfers (temporalis or masse-ter muscle) or microneurovascular muscle transfer is applicable.' Improvementsin microsurgical technique and instrumentation have yielded increasing successin restoring symmetric facial movement using microneurovascular muscle trans-fer from such muscles as the gracilis and latissimus dorsi. These muscles aretypically grafted to the upper lip and oral commissure. In a large study byO'Brien and Morrison7*with 59 such transfers, 88% of patients have had returnof function, and 48 have independent function of the two sides of the face.For all such rehabilitation strategies, reasonable expectation, for grafting too, isHouse-Brackmann grade 111-V.

CONCLUSIONThe facial nerve has many functions, perhaps the most physically obviousof which are the conveyance of emotion, eye closure, and assistance with speechand mastication. Because it is frequently paralyzed relative to other cranialnerves, much attention is paid to it. Future areas of interest will be more detailedmicrobiologic study of the nerve and larger DNA PCR studies of patients withBell's palsy, controlled studies of decompression for paralysis, better monitoringand care for the nerve during surgery of the temporal bone, more uniform

classification and treatment of paralysis, better electrical and radiologic testing,and better surgical restoration of function. It is hoped that the causes of paralysiswill become less controversial and that all medical practitioners will becomemore enlightened in their effective and rapid treatment.

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Address reprint requests toPeter G . von Doersten, MDRocky Mountain Eye and Ear Center, PC700 West Kent AvenueMissoula. M T 59801

the facial nerve current trends in diagnosis, treatment, and rehabilitation

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