Audiology Power Point Sarah Ochsner

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Your Very Own Ear
Probably more than you ever thought was in you!
Presented by Sarah Ochsner Introduction to
Audiology Sped 221
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The Peripheral and Central Hearing Mechanisms
Central Hearing Anatomy
Peripheral Hearing Anatomy

• Antihelix
• Antitragus
• Cavum conch
• Crus of helix
• Cymba Concha
• Helix
• Intertragal notch
• Lobe
• Tragus
• Triangular fossa
• Exernal Auditory Meatus

• Tympanic membrane
• Tensor tympani muscle
• Malleus
• Incus
• Stapes
• Stapedial muscle
• Footplate
• Oval window
• Round window
• Eustachian tube

• Vestibular
• Semicircular canals
• Ampullae
• Crista
• Utricle
• Saccule
• Auditory
• Cochlea
• Basilar membrane
• Organ of Corti
• Scala media
• Scala typania
• Scala vestibuli

• Vestibular
• Vestibular ganglion
• Cochlear
• Spiral ganglion
• Schwann cells

• Trapezoid body
• Superior olivary complex
• Lateral limniscus
• Inferior colliculi
• Medial geniculate body
• Auditory cortex
• Corpus callosum
• Vestiular nuclei
• Cochlear nuclei

Outer Ear
Middle Ear
Inner Ear
Central Auditory Pathway
8th Cranial Nerve
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Common Causes of Hearing Loss
This is a very short listing, as there are
literally hundreds of causes of hearing loss.
These are the most common. Click HERE to find out
more causes of hearing loss.
Conductive Mechanism
Sensorineural Mechanism

• Anotia
• Atresia
• Otitis externa
• Cerumen
• Microtia
• Carcinoma
• otomycosis
• Osteomas

• acute otitis media
• Cholesteatoma
• Eustachain tube
• Mastoiditis
• Myringitis
• Otosclerosis
• Tympanosclerosis
• Tympanic membrane perforation or rupture

• Meningitis
• Rubella
• Menieres disease
• Waardenburg syndrome
• Ototoxicity
• Toxoplasma
• Noise exposure

• Acoustic neuroma
• Auditory neuropathy
• Meningitis
• Schwannoma
• Vestibular neuritis
• Neurofibroma
• tumors

• Meningitis
• Encephalitis
• Congenital disorders
• Leukodystrophy
• Cerebral arteriosclerosis
• Tumors

Outer Ear
Middle Ear
Inner Ear
Central Auditory Pathway
8th Cranial Nerve
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Types of Hearing Loss
Hearing loss caused by a lesion in the outer or
middle ear. What does the audiogram look like?
Conductive -
Hearing loss caused by a lesion in the inner ear,
usually the cochlea, or auditory pathway. Show me
an audiogram of this.
Sensorineural -
A combination of conductive and sensorineural
loss, such as, when one ear has a conductive loss
and the other sensorineural. I want to see how
this audiogram compares.
Mixed -
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Degrees of Hearing Loss
0
Normal
10
Minimal
25
Mild
40
Hearing level in dB
Moderate
55
Moderately severe
70
Severe
90
Profound
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What's an audiogram?

• An audiogram is a snapshot of an individuals
  hearing ability. Various hearing tests are given
  to the individual and are recorded on the
  audiogram. The results are then interpreted by
  the audiologist and appropriate measures are
  taken.
• Different audiologists prefer different kinds of
  audiograms, but all of them essentially have the
  same information, including
• Air conduction
• Bone conduction
• Masked results
• Results of speech tests

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What's a tympanogram?

• A typanogram is a graph that represents the tests
  of the impedance and admittance of sound flow
  into the middle ear through the tympanic
  membrane. Basically, it measures the flexibility
  of the tympanic membrane.
• There are several different types of tympanograms

Normal peak either normal hearing or a
sensorineural loss
Low line Otitis Media Effusion High line TM
perforation, or patent PE tube
Negative Peak indicates a retracted tympanic
membrane because of negative air pressure,
probably as a result of fluid and/or otitis media
Shallow peak tympanic membrane is too stiff,
possibly as a result of tympanosclerosis or
otosclerosis
High peak the tympanic membrane is too flaccid,
possibly because of a break in the ossicular chain
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Immittance Tests
From http//www.skyrunner.com/baby/p_eartest.jpg
From www.digital-recordings.com/hearing-test
1. Tympanometry
Tests in which air pressure is varied and sound
is measured and which objectively measure the
tympanic membrane and inner ear. These tests are
visibly recorded in tympanograms. Each
tympanogram type can indicate different middle
ear problems, as previously explained.
2. Static Compliance
Tests that catch two snapshots of the mobility of
the tympanic membrane and inner ear. One
measuring point is at 200Hz, the other is at the
peak of the tympanogram. The acceptable range is
.22.5. If the range is too low, this indicates
a stiff tympanic membrane, possibly because of an
ear infection, otosclerosis, or tympanosclerosis.
If the range is too high, this indicates that
the tympanic membrane is too compliant, possibly
because of a broken ossicular chain, or just
excessive flaccidity.
Back to electrophysiological testing
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3. Ear Canal Volume (ECV)
An objective test that provides a measure of the
external ear canal, based on the principle that
the intensity of sound trapped in a closed cavity
is a direct function of cavity size. The volumes
are based on age Adults 1.01.5cc Children
.81.0cc Infants .5--.8cc Volumes greater than
2.5c suggest a perforation in the tympanic
membrane, or a patent PE tube.
4. Acoustic Reflex and Decay
Objective tests that provide information about
the reflex of the stapedial muscle in which the
acceptable range is 70-100 dBHL. Reflexes are
ordinarily present for fairly loud sounds,
relative to hearing ability. It is helpful in
distinguishing cochelar from neural hearing
losses. If the ART is Present at normal
threshold and sensation levels normal hearing
Present at normal thresholds but reduced
sensation levels cochlear loss Present at
elevated thresholds and sensation levels
retrocochlear loss Absent either retrocochlear
or really severe cochlear loss Reflex decaywhen
the stapedial muscle cannot sustain a contraction
for 10 seconds in response to loud noise. This
indicates a cochlear lesion. In order to do this
test an AR must be present.
Back to electrophysiological testing
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Speech Threshold Testing
1. Spondee Threshold
Test that is a measure of speech recognition
sensitivity which provides information about
hearing ability in primary speech ranges. It is
given by using spondees (two syllable word with
neither syllable stressed), either live or
recorded. It should be within 10dB of the Pure
Tone Average.
2. Speech Recognition Threshold
Tests that measures the lowest level at which
speech can be recognized correctly. Spondees are
also typically used for this test, although
sentences can be used. This is the most common
speech threshold test.
3. Speech Awareness Threshold
Test that measures the lowest level at which
speech can be detected. The SDT (Speech
Detection Threshold) is another name of this
test. It is used when a patient is unable to
respond to spondees.
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Speech Recognition Threshold Testing
Supra-threshold
1. Speech Recognition Ability
Test that measures the percentage of words the
patient can correctly report at supra-threshold
levels. Word lists or sentences can be used. An
audiologist can generally predict from degree of
hearing loss, type of hearing loss, and pure tone
results where this ability percentage will be.
The results will be compared with several other
normed data charts such as the Performance
Intensity Index, Audibility Index, and Lower
Confidence Limits.
2. Speech Recognition Threshold
Tests that measures the lowest level at which
speech can be recognized correctly. Spondees are
also typically used for this test, although
sentences can be used. This is the most common
speech threshold test.
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Central Auditory Testing
These tests are detectors of disorders within the
auditory pathways and the brain. They include
1. Synthetic sentences
These sentences are nonsensical with regard to
English grammar and syntax and are thus referred
to as synthetic. By asking patients to identify
sentences that have no context from which the
patient can make guesses, the audiologist is
given a more accurate reading of hearing and
processing abilities.
2. Dichotic sentences
This is a test in which two synthetic sentences
are delivered simultaneously in either ear and
the patient must distinguish from a prepared list
which two were given. This test provides
information about the corpus callosum and whether
or not information is making the necessary
crosses from hemisphere to hemisphere.
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Electrophysiological Testing
1. Immittance Tests
These tests were already discussed, and include
tympanometry, static compliance, ear canal
volume, and acoustic reflex and decay. If you
want to see them again, click on the names.
2. Evoked Potential Tests
Electrocochleography delivering clicks or pips
to the cochlea and measuring electrical
activity Auditory Brain-stem Response (ABR)
electrodes are used to deliver electric stimuli
to the brain. An ABR graph will show several
waves and troughs (to see an ABR, click here).
The waves are thought to be as follows IAuditory
Nerve, IIAuditory Nerve, IIICochlear Nuclei,
IIISuperior Olivary Complex, IVWho Knows.
Latencies between waves are compared to a normed
data chart. If latencies are abnormally long,
this may suggest nerual damage. The ABR is an
objective test that is now used widely to test
the hearing of newborns.
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Electrophysiological Testing, cont.
3. Otoacoustic Emissions Tests
These tests measure the motility of the outer
hair cells and possibly outer hair cilia in the
cochlea based on the premise that when sound
passes through the cochlea, the fluid within it
moves and thereby causes the OHCs to move. These
OAE tests are objective and are therefore used to
test newborns. There are two kinds Distortion
Product Otoacoustic Emission Test (DPOAE) when
the cochlea is stimulated simultaneously by two
pure tone frequencies whose ratio is between 1.1
and 1.3 Transient Evoked Otoacoustic Emission
Test (TEOAE) when the cochlea is stimulated by a
set of four clicks
One last thing...
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Give your ears a round of applause.
Thank you.