Definitions
Audiology
the study of hearing disorders, evaluation
Acoustic reflex testing
Stapedius muscle= A tiny muscle in the middle ear contracts when a loud sound occurs. The loudness level at which the acoustic reflex occurs—or the absence of the acoustic reflex—gives information to the audiologist about the type of hearing
loss, severity of hearing loss and the possible cause of hearing loss.
It is also a valuable test in detecting problems in the auditory pathway.
Acoustic reflex threshold: the lowest intensity level where that contraction occurs.
Type A
WNL
(Within Normal Limits) Normal ME system; normal pressure and compliance (normal middle ear pressure)
Degree of hearing loss
mild (16-40dB)
moderate (41-55dB)
moderately severe (56-65dB)
severe (66-89dB)
profound (90+dB)
Air conduction
Bone conduction
Air conduction: tests whole auditory system (OE, ME, IE, & beyond)
Bone conduction: tests inner ear and beyond. (skull bones (not ossicular chain) vibrate in response to sound waves too)
Tympanometry
the measurement of middle-ear pressure, determined by the mobility of the membrane as a function of various amounts of positive and negative pressure in the external ear canal.
More pressure = less mobility of middle-ear system. There are three types of tymps A, B, and C:
Auditory brainstem response
Response occurring during first 10 ms post-onset of stimulus
The auditory brainstem response (ABR) test gives information about the inner ear (cochlea) and brain pathways for hearing.
This test is also sometimes referred to as auditory evoked potential (AEP).
The test can be used with children or others who have a difficult time with conventional behavioral methods of hearing screening. The ABR is also indicated for a person with signs, symptoms, or complaints suggesting a type of hearing loss in the brain or a brain pathway.
The ABR is performed by pasting electrodes on the head—similar to electrodes placed around the heart when an electrocardiogram is run—and recording brain wave activity in response to sound. No response is necessary. ABR can also be used as a screening test in newborn hearing screening programs. When used as a screening test, only one intensity or loudness level is checked, and the baby either passes or fails the screen.
Type As
shallow
(ME pressure=normal) Getting a little movement, but it is more resistant. It’s having a harder time moving
normal pressure, reduced compliance; Lower peak
Could be Otosclerosis or scar tissue
Degree of hearing loss is determined by
Type of hearing loss is determined by
air conduction testing.
bone conduction scores.
Retrochoclear hearing loss
Functional hearing loss
Psychogenic hearing loss
Central auditory impairment
Retrochoclear hearing loss- VIII nerve and/or brainstem
Functional/ Non-Organic hearing loss- no organic basis can be found, usually resulting from attempt to gain something
Psychogenic/hysterical hearing loss- hearing loss resulting from emotional stress as unconscious means to escape from intolerable situation
Central auditory impairment (CAPD)- Auditory disorder within the neural pathways of central nervous system; Does not usually result in measurable hearing loss, but rather as detriments in reading and language skills
What does a Tympanometry evaluate?
ear canal volume, max peak pressure (x axis), peak compliance
Spondee words
SRT (speech recognition threshold): lowest level where an individual can understand speech at least 50% of the time.
SRT is established using spondaic words
SRT should be within 5dB of the pure tone average
Spondee words are even stressed two syllable words like "hotdog", etc.
Type Ad
deep
Too much movement of the ME structures but normal ME pressure.
Aka- Hypercompliance, Aka- Flaccid TM (Flopping ear drum—too much movement)
normal pressure, excessive compliance; High peak
Disarticulation of the ossicular chain
Conduction hearing loss
characterized by bone conduction thresholds being WNL with air conduction falling outside of normal limits.
The air bone gap will be greater than 10dB
Conductive and SNHL symptoms in a crowd
People with Conductive Hearing loss can hear their speech well so they tend to speak too softly, especially when there is background noise
People with Sensorineural Hearing loss have difficulty hearing themselves and others, so they speak more loudly. SNHL can have severe effects on articulation, resonance and voice.
Immittance testing
Determines status of ME
Differentiates cochlear versus retrocochlear disorders
Can also measure acoustic reflex
AC stands for
BC
AS
AD
X
O
>
<
AC – Air Conduction (headphones/inserts)
BC – Bone Conduction (oscillator on mastoid)
AS – shorthand for left ear
AD – shorthand for right ear
X – symbol for left ear on audiogram
O – symbol for right ear on audiogram
> - left ear unmasked bone conduction
< - right ear unmasked bone conduction
Type C
negative pressure.
Normal compliance, Abnormal ME pressure, retracted eardrum; negative pressure,
Eustachian tube disorders; colds/allergies
Senorineural hearing loss
characterized by air-conduction and bone conduction scores within 10dB (usually closer) of each other however both scores will be outside the normal range
Air bone gaps are usually not present
Difference between conductive, SNHL, and mixed
Conductive Hearing loss: malfunctions of outer or middle ear. Abnormal air, normal bone.; IE and beyond working normally
SNHL: malfunctions of inner ear and beyond.; cochlea (sensory) and/or VIII nerve (neural)Abnormal air, abnormal bone. Less than 10dB ABG. Permanent.; Recruitment: abnormally fast growth of loudness. (It goes with SNHL) a problem is in the cochlea; 75% of intelligibility is in the high frequency sounds
Mixed: malfunctions of outer and/or middle ear AND inner ear and/or beyond Abnormal air, abnormal bone, greater than 10dB ABG. Air is affected more than bone. Bone CAN’T be worse than air
Acoustic Immitance-
sometimes referred to as “impedance audiometry” measurements are made at the level in the plane of TM.
Measured using Tympanometry and Acoustic Reflex testing.
SNHL stands for
CHL
Mixed
SNHL – Sensory/Neural Hearing Loss
CHL – Conductive Hearing Loss
Mixed – SNHL and CHL present
Type B
flat (no measurement); flat configuration, no point of max compliance
No compliance, no MEP
It’s abnormal. The ME structures aren’t moving at all.
(If normal Ear Canal Volume): Otitis media or cholesteatoma (space occupying, doesn’t let the ossicles move),
(If abnormal Ear Canal Volume): TM perforation or PE tubes
(If small ECV): wax or poor probe placement
Mixed hearing loss
characterized by bone conduction scores being outside the normal range and the air conduction thresholds poorer than bone-conduction thresholds.
the air bone gap will be greater than 20dB.
What is the reason for a hole in the tympanic membrane
A hole in the eardrum (tympanic membrane perforation) is a common consequence of ear injury or infections. They can be repaired surgically to improve hearing and to prevent complications.