Hearing Evaluation

วัตถุประสงค์ เรียนรู้กระบวนการเกิดการได้ยิน รู้จักการประเมินการได้ยินของผู้ป่วย สามารถตรวจหาความผิดปกติของการได้ยินด้วยวิธีใช้ส้อมเสียง และส่งต่อผู้ป่วยอย่างถูกวิธี รู้จักการตรวจการได้ยินและการทดสอบที่เกี่ยวข้องต่างๆ

Contents Anatomy of the ear Hearing mechanism Tuning fork test Audiometry Tympanometry ABR,OAE

ANATOMY OF THE EAR

Mechanism of hearing

The pinna important to localized sound source in vertical plan Aids in localization more efficient at high frequency

Ear canal provide 10-15dB in 2500-6000Hz Best at 2500 Hz

EAC Open in oval 9-10mm.high, 8-9mm. wide, 25mm.long Average sound increase 10-15 dB

Human middle ear best transmission 500-2000 Hz

ME TM. Ossicle(M,I,S) Tensor tympani , Stapedius Stapedius response 85 dB

ME The area effect of the TM(55mm2) vs stapes footplate(3.2mm2), result in 17:1 increase sound energy Lever action of ossicular chain : handle of malleus 1.3 times longer than incus long process Total transform ratio is about 22:1(=25 dB)

AREA EFFECT & LEVER ACTION

Basic Hearing Test Tuning Fork Test Audiometry

HEARING TEST???

Tuning Fork Weber Test Rinne Test Bing Test Gelle Test Schwabach test

Weber Test Compare BC between Rt & Lt ear Sound is heard equally in both ears = no lateralization CHL : sound in poorer ear is louder SNHL : sound in better ear is louder

Rinne Test Compare AC & BC AC>BC = normal conducting system = Rinne positive BC>AC = CHL = Rinne negative Detect conduction defect เมื่อ ABG > 15 dB

Audiometry Pure tone audiometry Speech audiometry

Pure tone audiometry

Conductive hearing loss: criteria The BC better than the AC The air-bone gap at least 15 dB The BC must be normal The discrimination must be good

Sensorineural hearing loss : criteria The AC and BC threshold are reduced No air-bone gap

Figure 152-1. Audiogram showing a range of hearing loss.

Thai noise legislation Maximal noice allowance in workplace is 85 dBA for 8 hours work Cars generated noise limit to 85 dBA Residential area noise generated should not be > 60 dBA

คนพิการตามกฎหมาย Child < 7 years: hearing in speech frequency from the better ear > 40 dB > 7 years : > 55 dB

Speech audiometry SRT(speech reception threshold) SD Score (speech discrimination)

SRT (speech reception threshold) SRT is the lowest level in dB at which a patient can repeat spondee word in 50% (spondee คือคำ 2พยางค์ที่เสียงเทียบเท่ากัน เช่น eardrum) SRT should be within 10 dB of PTA

SDS(speech discrimination score) Percentage of phonetically balanced (PB)words(monosyllable) that patient repeats correctly Test contained 25 PB words at SRT +35 dB ถ้าต่ำมากคิดถึงretrocochlear lesion

Tympanometry Basic Principle Type Application

tympanometry Objective test that measure the mobility of TM (reflect of ME pressure) Five types: A, B, C, As, Ad

Type A; normal ME pressure Type B; flat fluid in ME , TM perforate Type C; negative pressureretract TM / ET dysfunction Type As;restric mobilityotosclerosis ,TM scar ,fixation of malleus Type Ad;hyper complianceflaccid TM ,ossicular disarticulation

Other Battery Test ABR (auditory brainstem response) EcoG (electrocochleography) OAE (Otoacoustic emissions)

ABR

Figure 152-7C. A, Audiogram, B, transient evoked otoacoustic emissions and C, auditory brain stem responses from a patient with a 7-mm intracanalicular left-sided acoustic neuroma.

electrocochleography EcoG measures the potential arising within cochlea and auditory nerve

EcoG Figure 151-1. Electrocochleography responses recorded from the human ear canal using condensation (C) and rarefaction (R) click stimuli. The major component of the whole-nerve action potential (N1), the summating potential (SP), and the cochlear microphonic (CM) are marked. The CM and the SP can be selectively enhanced by adding (R + C) or subtracting (R − C) the recordings made using rarefaction and condensation click. Ear canal negative deflections potentials are plotted as downward deflections. (From ASHA Workgroup on Auditory Evoked Potentials. The short latency auditory evoked potentials, Rockville, Maryland, 1987, ASHA, p 9, Figure 4 [based on work from Coates, 1981]. Copyright by the American Speech-Language-Hearing Association. Reprinted with permission.)

Normal Figure 152-8. Electrocochleogram obtained with a tympanic membrane surface electrode from a normal ear: the summating potential/action potential ratio is normal at 0.13.

Meniere’s Figure 152-9. Electrocochleogram obtained from the ear of a patient with M้ni่re’s disease: the summating potential/action potential ratio is elevated (0.81).

Otoacoustic emissions(OAEs) Confirm SNHL > 40dB Absent in cochlea lesion Present in neural lesion Objective test,noninvasive ,efficient Limited by conductive hearing loss

OAE Figure 152-6A. A, Transient evoked otoacoustic emissions and B, distortion-product otoacoustic emissions from the same normal-hearing ear.

OAE Figure 152-7B. A, Audiogram, B, transient evoked otoacoustic emissions and C, auditory brain stem responses from a patient with a 7-mm intracanalicular left-sided acoustic neuroma.

Historical risk factors for hearing loss in newborn Family history Hyperbilirubinemia requiring exchange Congenital infection (TORCHS) Craniofacial anormalies Birth weight less than 1500gm

Historical risk factors for hearing loss Bacterial meningitis Apgar scores ≤ 3 at 5 minutes Ototoxic medications > 5 days Prolonged mechanical ventilator (>10days) Stigmata or others findings associated with a syndrome known to include HL

การตรวจการได้ยินในเด็ก Since birth : objective tests ABR, OAE(otoacoustic emission) 6-30 months: behavioral tests 6-18 months Distraction test 6-30 months Visual Reinforcement Audiometry (VRA) > 30 months : Pure Tone Audiometry

Distraction test Visual Reinforcement Audiometry (VRA) Behavioral tests Distraction test Visual Reinforcement Audiometry (VRA)

Distraction test 6-18 months Child turns to localize the sound source

Visual Reinforcement Audiometry (VRA) Sound Head turn Visual stimuli

Visual reinforcement audiometry 6-30 months

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