hearing problems and tests exam 2

pure tone test

not measuring hearing, recording a set of behavioral responses to a set of acoustic signals that we interpret as representing hearing

threshold of audibility

defined as a set of minimum effect sound pressure level of an acoustic signal producing an auditory sensation in a specified fraction of trials—50% of the time

air conduction testing

involves a response following the normal route of hearing, ear canal—middle ear—cochlea

issues along the route to the cochlea

outer and middle—impacted cerumen—collapsed ear canal—issue in the middle ear—result in a conductive loss

bone conduction

direct stimulation of the cochlea via a bone oscillator place behind the ear via vibration of the temporal bone

bone conduction relationship to air conduction

it should never be worse since we are directly stimulating the cochlea, the response will always be better than or equal to the air conduction scores

hearing test results

tells us nothing about the impact or the patient’s individual issues

conductive hearing loss

result from issues in the outer and middle ear, the signal is not delivered to the inner ear because of issues in the OE and ME

sensorineural hearing loss

involve the cochlea, typically damage to the outer and or inner hair cells—retrocochlear involve issues—auditory nerve—to auditory cortex

mixed hearing loss

due to both issues in the OE and/or ME and issues in the cochlea

pure tone average

average of the thresholds at 500, 1000 and 2000 Hz

Issues involving the use of PTA

only used for the lay person, does not reflect frequencies above 2000 Hz, dB scale is logarithmic

speech reception threshold

lowest intensity in dB an individual can repeat or identify 2 syllable phonetically balanced words

speech detection threshold

lowest intensity in dB that an individual can tell the presence of speech—does not have to identify or repeat just detect the presence of sound

relationship between SRT, SDT, and pure tone thresholds

should be consistent with thresholds at 500, 1000, and 2000 Hz

dynamic range

difference in dB between threshold—speech or pure tones—and the point at which sounds become uncomfortable—UCL uncomfortable loudness level

dynamic range normal hearing vs hearing loss

normal hearing is large range as much as 100 to 110 dB. range narrows with hearing loss, recruitment—an abnormal growth in loudness—small increases in intensity very quickly become uncomfortable

word discrimination testing

repetition of one syllable—phonetically balance words—at a prescribed level above SRT in a sound treated room—no real relationship to the real world but it does give us an idea of the ability of that individual to understand speech

importance of speech testing

gives us a clue as to the impact of a hearing loss—also indicative of central processing

Intramural attenuation an air conductive signal and bone conducted signal (cross hearing)

approx 40 dB for an air conducted signal and 0 dB for a bone conducted signal

signal to noise ratio SNR

dB level of signal is what we want to hear, we always want a positive ratio—the level of the signal we want to listen to to the level of the background noise

difference between behavioral and objective tests

objective tests do not need any interpretation on the part of the patient

otoacoustic emissions—DPOAES—distortion product otoacoustic emissions

originate in the outer hair cells of the cochlea, an actual signal generated by distortion of the basilar membrane as sound travels up the basilar membrane, reflective of the sound we send into the cochlea, signal travels through ME into the ear canal, detected by a very sensitive microphone in the probe inserted in the ear canal

OAEs are not detected when

ME issues—fluid—negative pressure—holes in the TM, hearing losses greater than 30 dB (damage to outer hair cells)

OAEs tell us

if present, the outer hair cells are functional, but can be absent in individuals with normal hearing, typically used as a screening tool, can also be used to monitor cochlear function in individuals undergoing chemotherapy

can we use OAEs to estimate pure tone thresholds

no, a screening tool cannot be used for threshold

auditory evoked potentials

far field recording of the electrical activity of the neurological activity from the cochlea to the brainstem—takes approximately .5 msecs fir a signal generated in the cochlea to reach the brainstem—looking at brainwave activity before and after sound is introduced—can be used to determine threshold in an infant who failed an OAE screening—also can be used to detect tumors/growths on the auditory nerve—signal continues on to the auditory cortex, therefore could apply to auditory processing

time of onset of HL

congenital or acquired

time course of HL

acute, chronic, sudden, temporary, permanent, progressive, fluctuating

conductive hearing loss

involves issues in the outer and middle ear, generally are medically treatable, not usually longterm in most cases, compare AC to BC, remediation—generally responds well to amplification, degree is reflective of mass and stiffness

disorders—structural/malformations of the outer ear

embryologic development crania facial anomalies, congenital auricular malformations, microtia congenital fissure (low set ears, pits, or tags/atresia), TM perforations impacted cerumen Otitis Externa—swimmers ear, carcinomas

disorders of the middle ear

ET dysfunction, OM with and without effusion, conductive loss, upper respiratory, inflammation, treatment consists of abx, PE tubes, radical mastoid… otosclerosis, physical trauma, barotrauma, tympanosclerosis

otosclerosis

make things louder

sensorineural hearing loss

outer vs inner hair cells, malformations or trauma, X or Y linked hearing disorder, progressive loss in children during early childhood, common causes such as congenital, CMV, HIV, Rubella, Syphillis, mumps, serous labyrinthitis, herpes, ototoxicity, ahminoglycosides, heavy duty abx, cancer meds, aspirin, diuretics, industrial solvents… as we age, presbycusis… others, autoimmune, idiopathic sudden, acoustic trauma, physical trauma, radio necrosis

central nervous system

retrocochlear, effects on speech understanding, effects on sensitivity, brainstem disorders, infarcts blood flow interruption, gliomas—tumors, MS, temporal lobe, CVAs, receptive language