| - TITLE: Facial Nerve Paralysis SOURCE: Dept. of Otolaryngology, UTMB, Grand Rounds DATE: October 5, 1994 RESIDENT PHYSICIAN: John K. Yoo, M.D. FACULTY: Jeffrey T. Vrabec, M.D. DATABASE ADMINISTRATOR: Melinda McCracken, M.S. - "This material was prepared by resident physicians in partial fulfillment of educational requirements established for the Postgraduate Training Program of the UTMB Department of Otolaryngology/Head and Neck Surgery and was not intended for clinical use in its present form. It was prepared for the purpose of stimulating group discussion in a conference setting. No warranties, either express or implied, are made with respect to its accuracy, completeness, or timeliness. The material does not necessarily reflect the current or past opinions of members of the UTMB faculty and should not be used for purposes of diagnosis or treatment without consulting appropriate literature sources and informed professional opinion." I. Anatomy and Physiology A. The seventh cranial nerve is a complex nerve consisting of both motor and sensory components made up of about 10,000 fibers (7000 myelinated fibers innervate muscles of facial expression; 3000 unmyelinated fibers are sensory, secretomotor nerves). Three types of fibers subserving 3 functions: 1. Special Visceral Afferent: convey sense of taste from anterior 2/3 of tongue via the chorda tympani and lingual nerves to the geniculate ganglion; then, by way of the nervus intermedius to the tractus solitarius, ending in the nucleus of that tract. 2. Special Visceral Efferent: originates from the motor nucleus of the facial nerve and passes through the temporal bone (except the stapedial branch) to innervate auricular muscles, platysma, post. belly of digastric, stylohyoid, and superficial musculature of the face. 3. General Visceral Efferent: parasympathetic secretory fibers derived from the superior salivatory nucleus (preganglionic) and have three subsets of postganglionic fibers: a. Exit facial hiatus to enter greater superficial petrosal nerve where they synapse at the sphenopalatine ganglion; postganglionic fibers then innervate the lacrimal and palatine glands. b. Pass into lesser superficial petrosal nerve and synapse at the otic ganglion where postsynaptic fibers assist CN IX in the secretory supply of the parotid gland. c. Exits the temporal bone along the chorda tympani nerve to synapse at the submandibular ganglion where the postganglionic fibers innervate the submandibular and sublingual glands. 4. Evidence that CN VII has sensory afferent fibers from the EAC (believed to be responsible for otalgia in Bell's palsy and vesicular eruption in herpes zoster infection). B. The facial nerve and nervus intermedius exit the brain stem at the pontomedullary junction 1.5 mm anterior to CN VIII. They then follow a rostrolateral course through the cerebellopontine cistern for 15-17 mm entering the internal auditory canal. The facial nerve considered in 5 segments: 1. Meatal Segment: 23-24 mm in length; runs from the brain stem to the meatal foramen and lateral end of the IAC; Facial nerve occupies the anterior/superior quadrant within the IAC (anterior to crista verticalis or Bill's bar and superior to crista transversa). 2. Labyrinthine Segment: 3-5 mm in length, it is the shortest segment; extends from the meatal foramen to the geniculate ganglion within the narrowest part of the fallopian canal in an anterior/superior/lateral direction; greater superficial pertrosal nerve exits temporal bone anterior to geniculate ganglion through the hiatus of the facial canal; it is the only segment without anastomosing vascular arcades; at the geniculate ganglion, the nerve makes an acute 40-80o posterior turn to enter the middle ear. 3. Tympanic Segment: 8-11 mm in length, this segment courses posteriorly and inferiorly from the geniculate ganglion to the pyramidal eminence; the nerve curves inferiorly at an angle of 110-120o below the horizontal semicircular canal. 4. Mastoid Segment: 10-14 mm in length, it descends vertically to the stylomastoid foramen; by this point, branches to stapedius and chorda tympani have occurred. 5. Extratemporal Segment: 15-20 mm (prior to branching) in length; extends from stylomastoid foramen (10 mm inferior and medial to tragal pointer) to superficial facial musculature, post. digastric, stylohyoid, platysma, postauricular muscles. C. Blood Supply to Facial Nerve 1. Intratemporal nerve nourished by both the carotid and vertebrobasilar systems. 2. Labyrinthine branches of anterior inferior cerebellar artery (AICA) supplies meatal segment. 3. Petrosal branch of the middle meningeal artery supplies the perigeniculate area of CN VII. 4. Stylomastoid branch of the postauricular artery supplies the tympanic and mastoid segments. 5. There is a rich anastomotic vascular network to nourish the intratemporal facial nerve to prevent ischemia, except at the labyrinthine segment (junction of carotid and vertebrobasilar systems). This may explain its susceptibility in Bell's palsy, herpes zoster oticus, trauma. II. Pathophysiology of Nerve Injury A. Sunderland classification of nerve injuries based on histology of nerve trunk: 1. Class I (Neuropaxia): pressure on the nerve trunk causes conduction block at the pressure site, but there is no disruption of axonal continuity or connective tissue elements (i.e. endo-, peri-, epi-neurium all remain intact). When the pressure is removed, nerve can recover quickly and completely. No impulses cross the block, but stimulation of the nerve distal to the block can propagate impulses. 2. Class II (Axonotmesis): lesion is more severe than in class I injury, causing wallerian degeneration of the axon distal to the injury down to the motor endplate. Connective tissue elements remain intact, so nerve is able to regenerate to original destination if instigating insult is removed, albeit in a delayed fashion (nerve grows at a rate of 1 mm/day). Stimulus distal to the lesion not able to propagate impulse due to degeneration of the axon. 3. Class III (Endoneurotmesis): lesion is severe enough to cause disruption of axon and endoneurium; wallerian degeneration occurs. Regenerative process may result in incomplete recovery and/or synkinesis because the regenerating axons can grow into the wrong endoneurium or no endoneurium. 4. Class IV (Perineurotmesis): lesion causes disruption of axon, endoneurium, and perineurium. There is greater chance for aberrant regeneration than in class III injury. 5. Class V (Epineurotmesis): there is disruption of the axon as well as all connective tissue elements (endo-, peri-, epi-neurium). No chance for regeneration unless transected ends are surgically re-approximated. B. The histology of nerve injury from clinical studies show that in infections, there is diffuse edema and inflammation throughout the nerve, with maximal injury in the labyrinthine segment. In cases of trauma, there is retrograde edema and inflammation. These phenomena prevent accurate site of lesion determination by topognostic testing. III.Evaluation A. History 1. Onset (sudden vs. delayed) 2. Duration 3. Rate of progression 4. Complete vs. incomplete palsy (poorer prognosis with complete involvement). 5. Recurrent 6. Familial 7. Associated symptoms 8. Major medical illness: such as DM, cancer, sarcoidosis, auto-immune disorders, pregnancy 9. History of trauma 10. Previous surgery B. Physical Examination 1. Complete head and neck examination 2. Complete neurologic evaluation including cranial nerve exam 3. Evaluation of facial palsy a. complete vs. incomplete: incomplete palsies have satisfactory recovery of facial function; complete paralysis often portends a poorer prognosis, and requires quicker assessment and management. b. segmental vs. uniform involvement: central palsy of the face will manifest in only lower face weakness since the UMN of the upper face is bilaterally innervated; peripheral palsy of the face will manifest in weakness of both the upper and lower face; c. unilateral vs. bilateral: bilateral facial involvement suggests CNS pathology or systemic/generalized disease such as Guillain-Barre, DM, viral infection, sarcoidosis. d. House facial nerve grading system C. Laboratory Studies 1. Audiometry: helpful for evaluating facial palsy because of close proximity of CN VII and VIII and because of numerous problems arising within the temporal bone; should be performed in all evaluations of facial palsy. 2. Electrophysiologic tests (NET, MST, ENoG, EMG): helps determine endpoint of degeneration and prognosis for return of motor function, usually in preparation for surgery. 3. Topognostic tests to determine prognosis and site of lesion; not frequently used. 4. Radiographic studies: helpful for determining site of lesion, when etiology is unclear, when paralysis is recurrent, progressive, or atypical, and when facial palsy is due to trauma. a. CT: HRCT best for bone assessment; also helpful for mastoiditis, cholesteatoma, tumors, fracture assessment. b. MRI: superior to CT for soft-tissue evaluation; if done with gadolinium, can enhance lesions intrinsic to the facial nerve (Bell's, herpes zoster, facial schwannomas). 5. Labs: as indicated. IV. Topognostic testing These tests are based on principle that lesions distal to the take-off of a particular branch from the facial nerve trunk will spare the function subserved by that branch; less widely used for site of lesion determination and prognostication; lack of intracranial or intratemporal topographic organization of the facial nerve by animal studies; accuracy of topognostic tests disappointing, particularly in Bell's palsy where the lesion is diffuse throughout the nerve, but also for tumors, where a sharply defined site of lesion is expected. A. Schirmer test: tests greater petrosal nerve by measuring lacrimal secretions; filter paper placed in lower conjunctival fornix and amount of saturation produced within 5 minutes compared from side to side; considered significant if lacrimation of affected eye is less than half the amount seen on normal side, or if bilateral lacrimation combined reduced to 25mm or less; may be useful in predicting exposure keratitis. B. Stapedial reflex testing: tests branch to stapedius muscle past the 2nd genu in mastoid segment; measures contraction of stapedius in response to acoustic stimuli. C..Electrogustometry: tests chorda tympani nerve by assessing the ability of the tongue on the affected side to taste. D..Salivary flow: tests chorda tympani by measuring the amount of salivary flow; Wharton's ducts cannulated and the output is measured for 5 minutes; significant if there is 25% reduction between sides. E. Salivary pH: measures flow indirectly by measuring pH of the cannulated Wharton's duct (salivary pH rises as salivary flow increases); ph of 6.1 or less predicts incomplete recovery. V. Electrophysiologic Tests These tests are are useful for establishing prognosis for return of facial nerve function and for determining endpoint of degeneration by serial testing. Most useful for patients in whom decompression surgery is considered. Electrophysiologic tests provide no pertinent information during a paresis (has good prognosis), so done only for complete paralysis. NET, MST, ENoG are most useful in evaluating acute paralysis while nerve is in degenerative phase (because when the neuropraxic axons begin to recover, asynchronous depolarization, differing conduction velocities in motor axons, poor summation of the myogenic action potentials, and poor muscular contraction can give false-positive report of nerve status and once excitability is lost, further testing will be of no benefit). NET, MST, ENoG will show normal results for the first 3-4 days after nerve injury. This is due to the stimulating and recording electrodes being both distal to the lesion. It takes about 3-4 days for the nerve degeneration to reach the site of stimulation. Also NET, MST, ENoG will only work if the patient has unilateral involvement since the tests are predicated on the existence of a "normal" contralateral side for comparison. A. Nerve excitability test: stimulating electrode placed over the skin over the stylomastoid foramen. The lowest electric current (threshold) necessary to elicit a facial twitch on the paralyzed side is compared with the threshold value of the "normal" (contralateral) side. A difference of more than 3.5 milliamperes between sides portends a poor prognosis for return of facial function; not reliable. B. Maximal stimulation test: modified form of NET in which maximal rather than minimal stimulation is performed over peripheral branches of the facial nerve to depolarize all the motor axons beneath the stimulating electrode. Stimulator setting increased to the level of patients' tolerance. Paralyzed side compared subjectively to "normal" side and graded as equal, slightly decreased, markedly decreased, and absent. Latter two grades suggest advanced degeneration and a poor prognosis; superior to NET. f C. Electroneurography: facial nerve is stimulated transcutaneously at the stylomastoid foramen with bipolar electrodes. Responses to maximal electrical stimulation are recorded by bipolar electrodes placed usually at the nasolabial groove. The peak-to-peak amplitude of the evoked compound action potential is proportional to the number of intact motor axons and is compared to the amplitude of the normal side. Greater than 90% degeneration compared to the normal side indicates a poor prognosis; considered to be an accurate prognostic test; equivalent to evoked EMG. D. Electromyography: measures muscle action potentials generated by voluntary and spontaneous activity via needles inserted into the facial muscles. No active stimulation is needed. Electrical silence can be caused by normally innervated muscle in a resting state, severe muscle wasting, or facial paralysis in the acute stage. Voluntary potentials seen during voluntary contraction. Fibrillation potentials represent involuntary, invisible contractions of a single denervated muscle fiber, indicating degeneration of the muscle's nerve supply and usually appear 10-14 days after nerve injury. Polyphasic potentials are seen during nerve regeneration and may be seen as early as 4-6 weeks after onset of paralysis. May be complementary to NET, MST, and ENoG during the first 3-4 days after injury. If voluntary active motor units are present, nerve is probably intact with incomplete injury, but if active motor are not present, there is some undetermined degree of facial nerve injury because EMG's cannot differentiate totally neuropraxic nerve from a completely degenerated one. E. Nerve conduction time: similar to EMG; stimulus large enough to evoke maximal response delivered through stimulating electrode at stylomastoid foramen and recorded by electrodes over facial muscle groups; latency for each compound action potential is the time between onset of stimulus and onset or response; upper limits of normal: adults-4msec. neonates/infants-7-10 msec.; least reliable prognostic test. F. Trigeminal blink reflex: percutaneous stimulation of supraorbital nerve causes a blink reflex that is recorded by electrodes placed over the orbicularis oculi muscles; measures conduction in the intracranial/intratemporal portion of facial nerve by taking advantage of of the reflex arc between afferent trigeminal nerve and efferent facial nerve; only prognostic test that measures central pathology of facial nerve; considered investigational. G. Magnetic evoked neuromyography (MNoG): magnetic transtemporal stimulation is produced by a magnetic coil which generates a magnetic field that passes unattenuated by soft tissue to induce an in- depth electrical field; compound muscle action potentials measured at nasolabial groove with bipolar electrodes; benefits include direct stimulation of intracranial portion of facial nerve proximal to the lesion (eliminates the delay asso. with the standard electrodiagnostic tests waiting for wallerian degeneration to reach the site of measurement); there is also decreased pain with MNoG compared to electrical stimulation; remains investigational as it is difficult to determine site of lesion with such a large magnetic/electric field. VI. Causes of facial palsy Sifting through the extensive differential diagnosis of facial palsy is difficult but important to differentiate between those that resolve without intervention from those that are treatable and may be life-threatening. In the majority of cases, the cause will not be found and a diagnosis of Bell's palsy will be made. A. Bell's palsy 1. Accounts for over half of the cases of facial palsy and is the most common cause; traditionally considered a diagnosis of exclusion, but recently, considered a positive diagnosis based on specific clinical features: a. unilateral paralysis/paresis of all muscle groups b. onset sudden c. no evidence of CNS disease d. no evidence of otologic or cerebellopontine angle disease e. evidence of concomitant sensory cranial polyneuritis. 2. Incidence: overall 20-30 per 100,000, but increases with age; M:F ratio equal, but twice as common in females for 10-19 year age group and 1.5 times more common in males for >40 age group; pregnant women have 3.3 times greater risk than same-aged nonpregnant women; left/right sides equally involved with less than 1% bilateral; recurrence rate about 10% and can be ipsi-/bi-lateral; diabetics have 4.5 times more risk to develop Bell's palsy; family history of Bell's palsy present in 10% of patients. 3. Etiology: exact etiology still unknown. Theories include: a. Viral cause has been proposed, especially herpes simplex. Supported by the facts that acute facial paralysis can occur 2o to mumps, rubella, EBV, and herpes simplex, and that there is an increased incidence of antibodies to herpes simplex than in age-matched controls, as well as animal studies in which facial paralysis induced by inoculation of herpes simplex virus type I on surface of facial nerve. b. Autoimmune cause has also been suggested by complement component studies during acute stage of Bell's palsy. May be a combination of both, i.e. autoimmune neuritis preceded by viral infection? c. Most likely site of lesion is at the junction of the IAC and the labyrinthine portion of fallopian canal (meatal foramen). The meatal foramen is the narrowest part and the facial nerve occupies the greatest proportion of the lumen. Also, labyrinthine segment is the anastomotic junction ("water-shed area") between the carotid and vertebrobasilar artery systems making it more susceptible to ischemic areas. There is also intraoperative EMG evidence of nerve conduction blockade. Labyrinthine segment enhances on gadolinium-enhanced MRI. Histologic studies show diffuse demyelination of the facial nerve with lymphocytic infiltration, especially at the labyrinthine segment. 4. Diagnosis a. History: onset usually sudden often preceded by viral prodrome; symptoms include facial numbness, epiphora or decreased tearing, pain (usually retroauricular), dysgeusia, hyperacusis or dysacusis (occurs even with intact stapedial reflex; represents dysfunction of the cochlear division of the acoustic nerve because of interruption of the inhibitory fibers that traverse the cochlear ganglion). b. Physical exam: includes hypesthesia or dysesthesia of cranial nerves V and IX and second cervical nerve. Paralysis of motor branches of X may also be seen as deviation of soft palate/uvula or as shortening of one vocal cord with rotation of the posterior larynx to the affected side. These findings suggest that Bell's palsy is a part of a cranial polyneuropathy (CN VII being the most evident due to anatomy of the meatal foramen) rather than an isolated involvement of CN VII. c. Radiographic studies: HRCT and/or MRI in cases of uncertain diagnosis, recurrence, or atypical Bell's palsy. 5. Natural course and Prognosis: Onset usually sudden and runs its course within first 2-3 weeks; 85 % of the patients have evidence of recovery during this time frame; remaining 15% go on to develop complete degeneration and will not show recovery for 3-6 months (11% at 3 months, 3% at 4 months, 1% at 5 or more months). Ninety percent of patients will have evidence of recovery in 1 month. The longer the time needed for recovery, the greater the probability of sequelae. In general, prognosis is excellent for return of facial function. Complete recovery in 80-90% of the patients. Single most important prognostic factor is whether the palsy is complete or incomplete. Patients who never develop complete paralysis will recover with no sequelae in 95-100%. 6. Treatment a. Observation alone indicated for patients in whom steroids or acyclovir is contraindicated; eye care measures should be instituted. b. Eye care: liberal use of natural tears while awake; application of Lacri-lube during sleep; tarsorrhaphy rarely necessary; taping the lower eyelid in a superolateral direction needed when ectropion is present; avoidance of wind, fans, dust with shielded glasses. c. Steroids: oral prednisone (1 mg/kg divided BID) may be helpful in preventing or lessening degeneration, synkinesis, progression of palsy, relieving pain, and hastening recovery. Patient should be evaluated on 5th or 6th day following onset of paralsis. If paresis, taper over the next 5 days. If not, give full dose for 10 more days, followed by taper over 5 days. d. Acyclovir: can be given with steroids in cases of Bell's palsy especially if pain is present (perhaps representing a forme fruste of herpes zoster). Preliminary studies show it to improve recovery in Bell's palsy. e. Surgical decompression: although controversial, middle fossa decompression has been advocated for complete decompression of the entrapment area at the meatal foramen and labyrinthine segment; performed if ENoG shows greater than 90% degeneration within the first 2 weeks after onset or if suffering from recurrent palsy (contraindicated in infected ear or in only hearing ear). Fisch showed that 64% of the patients had Grade I/II recovery without decompression, 79 % of the patients had Grade I/II recovery with decompression performed within 24 hours of advanced degeneration occuring 1-14 days after onset of facial palsy. B. Trauma 1. Various forms of trauma to the facial nerve can occur: GSW, penetrating knife-wound, blunt trauma, and iatrogenic injuries during surgery; trauma can occur in various locations on the facial nerve: intracranial, intratemporal, extracranial; type and location will dictate management and outcome; 2nd leading cause of facial palsy behind Bell's palsy. 2. History will usually reveal traumatic nature of facial palsy. Immediate paralysis after the inciting event suggests penetrating injury to the nerve with transection, whereas delayed injury suggests progressive neural edema, with an intact nerve. 3. Physical exam: if 1o and 2o assessments of patient do not reveal any significant abnormalities, evaluate facial palsy thoroughly. 4. Objective studies: a. Audiometry to assess any possible hearing loss. b. CT scan for temporal bone fractures and intratemporal GSW's to evaluate fractures and bone destruction. c. Carotid arteriography when indicated, especially in cases of penetrating injuries to the temporal bone to rule out injuries to the carotid or jugular systems. d. Electrophysiologic testing if paralysis is complete, delayed onset, and surgical exploration/decompression is considered. 5. Types of trauma-induced facial nerve paralysis and their treatments: a. temporal bone fractures: most common cause of traumatic injury to the facial nerve; two types depending on orientation of the fracture plane to the long axis of the petrous pyramid: i. longitudinal fractures: parallel to long axis of the petrous pyramid lateral to otic capsule; can result in CHL; 20% result in facial palsy; vast majority occur in perigeniculate area. ii. transverse fractures: perpendicular to the long axis of the petrous pyramid through the otic capsule; can result in profound SNHL; 50% result in facial palsy; injury occurs in the perigeniculate area or in the tympanic segment above the oval window. iii. with complete facial paralysis, obtain CT- temporal bone with 1 mm cuts to observe perigeniculate region for fracture; if fracture is present, surgically explore; if delayed onset paralysis, get facial nerve testing on day 4 after onset; if advanced degeneration of the facial nerve has occurred or if paralysis is immediate onset with or without fracture, surgically explore with trans-mastoid/middle fossa approach (contraindication is intracranial injury as this approach requires retraction of the temporal lobe); use trans- mastoid/trans-labyrinthine approach in the absence of functional hearing; re- anastomose transected nerve if possible; otherwise, perform interpositional grafting with greater auricular or medial antebrachial cutaneous nerve. b. Intratemporal GSW: produce facial nerve paralysis in greater than 50% of the cases; can be injured directly or by the kinetic energy imparted by the projectile or by bony fragments; usually involves mastoid or tympanic segments and stylomastoid foramen area; evaluate with CT, angiography, audio, and if facial nerve testing shows advanced degeneration, perform trans- mastoid/middle ear exploration to anastomose or interposition graft transected nerve. c. Intratemporal iatrogenic injury: incidence of facial nerve injury during middle ear and mastoid surgery 1%; if iatrogenic transection or herniation through sheath defect occurs intraoperatively, repair injuries immediately; if paralysis is discovered post-op and surgeon is certain no injuries to facial nerve occurred intra-op, get CT-temporal bones immediately, perform facial nerve testing on post-onset day #4, and explore the wound only if advanced degeneration is evident. d. Extracranial soft-tissue injury: penetrating wounds near proximal distribution of the facial nerve need to be explored; transections of the main trunk of the facial nerve or the larger temporofacial or cervicofacial branches need to be repaired by reanastomosis or interpositional grafting with medial antebrachial cutaneous nerve or greater auricular nerve at the time of soft-tissue closure; wounds medial to the lateral canthus of the eye need to be explored and transected ends repaired if possible, but repair not absolutely needed if aggressive exploration is required due to the rich anastomotic network of the facial nerve branches in the mid-face. C. Infections 1. Infections are the 3rd leading cause of facial nerve palsy, behind Bell's palsy and trauma. 2. Herpes zoster facial palsy a. manifestation of dormant herpes zoster or varicella virus reactivating in extramedullary cranial nerve ganglia during a period of decreased cell immunity. b. 5-9% of patients with peripheral facial palsy are due to herpes zoster virus; incidence increases with age presumably as immune response decreases with age. c. in herpes zoster oticus, the simplest form, there is severe otalgia and vesicular eruption of the EAC and concha; coexistence of facial palsy and vesicular eruption over the distribution of a cranial nerve (V, VII, IX, X) or cervical plexus makes up the Ramsay-Hunt syndrome. Patients may also have varying degrees of SNHL as well as vestibular symptoms, and are more likely than Bell's palsy patients to have associated cranial nerve symptoms. d. labs often show the rise and fall of antibody titers specific for the virus. e. severity of palsy is worse and the prognosis is poorer in comparison with Bell's palsy. Only about 50% regain full facial function, as opposed to 90% in Bell's palsy. Degeneration with herpes zoster oticus occurs more slowly (over the course of 3 weeks) than in Bell's palsy in which degeneration proceeds quickly within the first 2 weeks. f. treatment includes systemic steroids which reduces pain, vertigo, and postherpetic neuralgia, as well as acyclovir which decreases pain, promotes resolution of vesicles, and suggested by some to hasten return of facial function. Surgical decompression has not been proven beneficial for herpes zoster oticus. 3. Otitis media a. facial palsy can occur as a complication of acute suppurative otitis media, COME, and mastoiditis; most are incomplete paralysis and may be due to a dehiscence of the bony canal of the facial nerve allowing spread of inflammation to involve the nerve. b. For acute suppurative otitis media, perform wide myringotomy with drainage and cultures to direct antibiotic therapy; audiometry to evaluate inner ear; CT scan useful to rule out mastoiditis or mass lesion; generally treated medically. c. facial palsy associated with chronic otitis media suggests cholesteatoma, which causes facial paralysis by compression or inflammation; surgery is indicated. d. facial palsy due to coalescent mastoiditis is a surgical problem; perform myringotomy and drainage of the middle ear along with IV antibiotics followed by mastoidectomy to remove infected bone. e. facial palsy usually resolves with aggressive management of the infection; prognosis associated with facial palsy due to acute OM better than that associated with chronic OM. 4. HIV a. acute facial palsy can occur at any stage of HIV infection; palsy can be due to direct involvement of the facial nerve/ganglion by the virus, secondarily from immunodeficiency (i.e. secondary infection by herpes zoster), or as part of an acute inflammatory demyelinating polyneuropathy seen in early stages of HIV infection. b. treatment and prognosis dependent on underlying pathology. D. Tumors 1. only about 5% of the cases of facial palsy is due to tumors. 2. be wary of neoplasm with: history of cancer, associated facial twitching, multiple cranial nerve deficits, no return of facial function despite adequate opportunity for recovery, recurrent ipsilateral palsy, paresis evolving slowly and gradually over a period of time exceeding 3 weeks, neck or parotid mass. 3. most common benign tumor involving the nerve is facial schwannoma; presents with slowly progressive paresis, facial twitching, middle ear mass, or conductive hearing loss; usually involves labyrinthine, tympanic, and mastoid segments; most common malignant tumors involving the nerve are adenoid cystic and mucoepidermoid carcinoma. 4. management depends on location, size, and aggressiveness of neoplasm (benign vs. malignant), but may involve transposition, rerouting, division and reanastomosis, interpositional grafting, and cranial nerve crossover; best possible result following grafting of the facial nerve is House grade III. E. Facial palsy in the newborn 1. Incidence of facial paralysis in the newborn estimated at 0.23%; prognosis is excellent, especially if trauma-related. 2. Causes a. Trauma (75-80%): suggested by isolated facial paralysis with signs of trauma including facial contusion, ecchymosis over the course of the facial nerve, and/or hemotympanum; mechanism of injury believed to be compressional molding of the head as it passes through the birth canal or the use of forceps. b. Congenital (15-20%): suggested by the presence of other abnormalities without evidence of trauma; some congenital causes of facial palsy include: i. CULLP (congenital unilateral lower lip palsy): defect limited to absent depressor labii inferioris muscle activity. ii. Mobius syndrome: broad range of manifestations including isolated unilateral facial palsy to bilateral VII nerve paralysis, uni- or bi-lateral VI palsy, other cranial nerve anomalies, skeletal deformities including absence of pectoralis major muscle. iii.Goldenhar's syndrome (oculoauriculovertebral dysplasia): defects of the 1st and 2nd branchial arch structures; anomalies include preauricular tags, auricular deformities, EAC atresia, ossicular malformations, VII nerve hypoplasia, absence of chord tympani, shortening and narrowing of IAC, colobomas, vertebral anomalies. iv. Dystrophia myotonia: familial, progressive distal myopathy; congenital facial diplegia with muscle wasting. v. Thalidomide embryopathy (Miehlke syndrome): phaecomelia, microsia, CN VI palsy, facial nerve paralysis, SNHL. c. within the first 3 days of life, a complete paralysis should undergo electrophysiologic testing to differentiate between congenital vs. traumatic cause. In traumatic injuries, the nerve can be stimulated for 3-5 days post- injury with fibrillation potentials visible at 10- 14 days. In congenital causes of facial palsy, the ability to stimulate the nerve will probably be absent at birth with no fibrillation potentials visible on EMG. d. in trauma related facial palsy, prognosis is excellent and surgical decompression not warranted until nerve has had a chance to recover; congenital paralysis best left untreated until late childhood at which point facial reanimation can be undertaken. F. Other 1. Melkersson-Rosenthal syndrome: triad of recurrent facial palsy, orofacial edema, and lingua plicata (fissured tongue), although all three features present in only quarter of the patients; begins in teens; etiology is unknown; treatment consists of symptomatic measures; reports of facial nerve decompressions helpful in stopping recurrences of facial paralysis. 2. Diabetes mellitus: patients with DM have about 5 times greater chance of developing Bell's palsy than age-matched controls. 3. Sarcoidosis: chronic, non-caseating granulomatous disease with various manifestations; 5% have cranial nerve involvement, but CN VII is the most common one; due to invasion of nerve by granulomatous process; facial paralysis can be bilateral; diagnose with ACE levels; treat with steroids. VII. Approaches to facial nerve decompression A. Retrolabyrinthine approach/Retrosigmoid approach 1. Generally not useful for decompression B. Middle cranial fossa (transtemporal) approach 1. Internal auditory canal porus to tympanic segment 2. Advantages a. can expose entire IAC and labyrinthine segment with hearing preservation (most commonly used for decompression in Bell's, herpes zoster oticus, and longitudinal temporal bone fractures). 3. Disadvantages a. anatomy of the area is variable and may be difficult identifying landmarks b. dural elevation may be difficult if dura is tightly adherent to middle cranial fossa floor resulting in dural tears c. CHL or SNHL can occur C. Transmastoid approach 1. Geniculate ganglion to stylomastoid foramen 2. Advantages a. excellent exposure of mastoid segment; tympanic segment may be obscured by ossicles (incus may have to be removed to gain adequate exposure). 3. Disadvantages a. limited access to geniculate ganglion; cannot reach labyrinthine segment b. CHL or SNHL can occur D. Translabyrinthine approach 1. Total facial nerve 2. Advantages a. access to entire nerve through one approach (used for transverse temporal bone fractures, extensive facial neuroma, or large cholesteatoma extending into IAC) 3. Disadvantages a. hearing and balance must be sacrificed to use this approach, so cannot use if cochlear and vestibular function exists. - BIBLIOGRAPHY Adour KK, et. al. The true nature of Bell's palsy: analysis of 1000 consecutive patients. Laryngoscope 88:787, 1978. Adour KK, Wingerd J, Doty HE. Prevalence of concurrent diabetes mellitus and idiopathic facial paralysis (Bell's Palsy), Diabetes 24:449, 1975. Bailey, Byron J., ed. Head and Neck Surgery-Otolaryngology. Philadelphia, PA.: J.B. Lippincott Co., 1993. Cummings, Charles, ed. Otolaryngology-Head and Neck Surgery. St. Louis, MO.: Mosby- Year Book, Inc., 1993. Delaney P. Neurologic manifestations in sarcoidosis. Ann Intern Med 87:336, 1977. Devriese PP, Moesker WH. The natural history of facial paralysis in herpes zoster. Clin Otolaryngol 13:289, 1988. Fisch, Ugo. Surgery for Bell's palsy. Arch Otolaryngol 107(1):1-11, 1981. Gates, George A. Current Therapy in Otolaryngology-Head and Neck Surgery. St. Louis, MO.: Mosby-Year Book, Inc., 1994. Hilsinger RL, Jr., Adour KK, Doty HE. Idiopathic facial paralysis, pregnancy, and the menstrual cycle. Ann Otol Rhinol Laryngol 84:433, 1975. Lee, K.J., ed. Essential Otolaryngology. New York, NY: Elsevier Science Publishing Co., Inc., 1991. Management of Facial Nerve Disorders. The Otolaryngologic Clinics of North America. June 1991. May, M. The Facial Nerve. New York, NY.: Thieme-Stratton, 1986. McHugh HE, Sowden KA, Levitt MN. Facial paralysis and muscle agenesis in the newborn. Arch Otolaryngol 89:157, 1969. Peitersen E. The natural history of Bell's palsy. Am J Otol 4:107, 1982. -END | |
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