耳鼻咽喉头颈外科学：耳聋防治

1、Hearing Loss“A blind person is cut off from the world of things, whereas one who is deaf is cut off from the world of people.” 耳聪心慧舌端巧， 鸟语人言无不通。Our understanding of hearing is less developed compared with that of other senses, in part, because the organ of hearing is hard to access: the cochlea is b

2、uried in the petrous temporal bone.Learning Objectivesetiologydiagnosis treatmentEtiologyLudwig Van Beethoven - syphilis ？Thomas Edison - explosive deafness ？ Helen Keller (1880-1968) - genetic hearing lossHow do We Hear Sounds?Anatomy of the EarAir conduction: The atmospheric transmission of sound

3、to the inner ear through the external auditory canal and via structures of the middle ear.Bone conduction: conduction of sound waves to the inner ear through the bones of the skull.Area ratioThe eardrum is about 17 times larger than the oval window.55mm2/3.2mm2=17Lever: ossicular chain Crowbar, 1.31

4、7X 1.3=22.1These structures amplify the sound pressure about 22.1 times when the sound interacted with the oval window. Tube is divided into 3 fluid-filled chambersScala vestibuli, cochlear duct, scala tympaniOval window attached to scala vestibuli (at base of cochlea). Vibrations at oval window ind

5、uce pressure waves in perilymph fluid of scala vestibuliScalas vestibuli & tympani are continuous at apexSo waves in vestibuli pass to tympani & displace round window (at base of cochlea)Oval windowRound windowMovement of stapes foot causes perilymph flow and variations in round window membrane, and

6、 finally variations in cochlear basilar membrane.Oval windowOval windowRound windowOval windowVariations in cochlear basilar membrane cause excitation of hair cells. Low frequencies can travel all way thru vestibuli & back in tympani.As frequencies increase, the sound waves travel less.Travelling wa

7、ve theory-Bekesy High frequencies produce maximum stimulation of Spiral Organ closer to base of cochlea & lower frequencies stimulate closer to apex.Hearing Loss DeafnessHearing lossHearing impairment Deaf is a total lack of hearingDeafness has connotations of discriminationDegrees of hearing lossMi

8、ld 2040dBModerate 4155dBModerate-severe 5670dBSevere 7190dBProfound 90dBClassficationsConductiveSensorineural: sensorial, neuralMixedCongenital: hereditary, non-AcquiredPrelingualPostlingual Syndromic Non-Hearing loss (HL) - classificationConductive-any interruption of passage of acoustic energy bet

9、ween pinna and oval window.External auditory canalTympanic membraneMiddle earConductive External acoustic meatusAuricleMicrotia/AnotiaConductive - Tympanic MembranesPerforation (hole)RetractionConductive Ossicular chainMalleus (hammer)Incus (anvil)Stapes (stirrup) smallest bone of the bodyAbsenceSti

10、ffnessOtosclerosisTympanosclerosisDislocation (trauma)CholesteatomaTumorsHearing loss (HL) - classificationSensorineural - any damage to the organ of Corti or VIII nerve pathway or auditory cortex(SNHL)Sensorineural Hearing LossSensoryNoiseNoise-induced hearing lossAcoustic traumaInfectionGeneticNeu

11、ralTraumaDegeneration (Presbycusis)TumorsPresbycusisHeredityInfectionsNoise InducedOtotoxicityMenieres DiseaseTraumaSudden idiopathic/viralMetabolic (diabetes mellitus)AutoimmuneNeoplasm (acoustic neuroma)Congenital hearing loss and hereditary hearing lossCongenital hearing loss: hereditary hearing

12、loss, Non-. Genetic factors cause more than 50% of congenital hearing loss in children, may be autosomal dominant, autosomal recessive, or X-linked. Non-genetic Intrauterine infections including rubella, cytomegalovirus, and herpes simplex virus Prematurity Maternal diabetes Toxemia during pregnancy

13、 Lack of oxygen PresbycusisAge related decline in auditory function.Speech discrimination is affected commonly.Pathology: aging, noise, heredity, head injury, infection, and circulation problems such as high blood pressure.Hearing AidCochlear ImplantSNHL due to infective diseaseMost common Adult SNH

14、L viral cochleitisChildren SNHL meningitis H.influenza supperative labyrinthitisViral .Mumps(流行性腮腺炎) unilateral SNHLMeasle (麻疹) bilateral SNHLRubella 风疹病毒Cataracts, cardiac defects, HL白内障，心脏病，听障Cytomegalovirus 巨细胞病毒（CMV）Etiology: 1-2% of live birthsOnly 10% patients have symptoms such as HL, mortali

15、ty 30%-40%Syphilis 梅毒Congenital syphilis is a known cause of progressive sensorineural hearing loss. Ototoxicity is the therapeutic agents and other chemical substances to cause functional impairment of the inner ear, and especially of the end organs and neurons of the eighth cranial nerve.Approxima

16、tely 200 drugs have been labeled ototoxic. Ototoxicity氨基糖甙类抗生素：链霉素、庆大霉素、卡那霉素、新霉素、妥布霉素等多肽类抗生素：万古霉素Vancomycin和多粘菌素polymyxins抗肿瘤药：氮芥、順铂等利尿类药物：利尿酸、速尿等水杨酸类药物抗疟药：奎宁等砷剂酒精中毒、烟草中毒、CO中毒，磷、苯、砷、铅等中毒Aminoglycoside ototoxicityAntibiotics from the aminoglycoside family cause severe damage to hair cells in a dose-d

17、ependent manner. Progressive damage of hair cells Noise-induced hearing lossTemporary Threshold Shift (TTS)Permanent Threshold Shift (PTS)Difficulty hearing high frequency sounds : 3-6-kHzPoor speech discriminationTinnitusDamaged Hair CellsNormal Hair CellsTrauma hearing lossTemporal bone fracture 2

18、0% Transverse fracture SNHL (labyrinth tear) , facial nerve pulsyOtic Barotrauma Sudden pressure change perilymph fistulaIdiopathic sudden hearing lossSNHI least 30 dB in 3 frequency in one dayCommon unilateral No involvement of other cranial nerves Idiopathic : Viral theory, Vascular theory, Others

19、40-70% recoverAutoimmune hearing lossThe hallmark is its rapid, and sometimes fluctuating, progression to hearing loss in both ears occurring over a period of weeks to months. No specific tests. Corticosteroids Acoustic NeuromaAuditory NeuropathyAN is a hearing disorder in which sound enters the inn

20、er ear normally but the transmission of signals from the inner ear to the brain is impaired. Poorer thresholds in the low frequencies.Speech discrimination poorer than behavioural audiogram would suggest AN.Normal evoked otoacoustic emissions (EOAE) and absent or markedly disturbed auditory evoked p

21、otentials from the brainstem and/or cortex.Hearing loss (HL) - classificationCan be “mixed” conductive & sensorineuralHearing testsTuning Fork TestsClinical - tuning forks: 256 or 512Hzsimple, quick andaccurate means to differentiate CHL and SNHL.Rinne testTests air conduction much more efficient th

22、an BCACBC, + Rinne, normal hearing and SNHL BCAC, - Rinne false - RinneWeber testAssymetrical conductive lossVery sensitive in compliant patientIf CHL unilateral as little as 5 dB detectedSchwabach Test It compares pts hearing sensitivity with that of an examiner.Pure Tone Audiometry AUDITORY BRAINS

23、TEM RESPONSE (ABR)ABR is a neurologic test of auditory brainstem function in response to auditory (click) stimuli. Origin of each waveWaveOriginICochlear nerveIIDorsal & Ventral cochlear nucleusIIISuperior olivary complexIVNucleus of lateral lemniscusVInferior colliculusVIMedial geniculate bodyVIIAu

24、ditory radiation (cortex)Otoacoustic Emissions (OAE)Applicationneonatal hearing screeningdifferential diagnosismonitoring cochlear damageAcoustic immittance audiometry It is used to evaluate the status of the external and middle ears and of the acoustic reflex arc. It includes tympanometry, static-compliance testing, and acoustic reflex measures. Treatment Treatment PharmacySurgery Implant cochlearHearing aidOther SurgeryImprove hearingTymplanoplastyOssicle Chain Reconstructi