Audiology

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Audiology

• Course Development Sara Danielson
• Kathryn Leth
• Course outline, organization editing Paul A.
  Hayden Ph.D.

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I. Anatomy of the Hearing Mechanism

• A.) Outer Ear
• B.) Middle Ear
• C.) Inner Ear
• D.) Neurology of Hearing
• www.theearfound.com/anatomy.html

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Outer Ear

• 2 Components
• -Pinna or Auricle
• External Auditory Meatus (EAM)
• ¼ ? resonator
• High frequency amplifier
• Trigeminal (V) and Vegas (X)

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Middle Ear

• Components
• I. Tympanic Membrane (TM)
• Pars Tensa
• Pars Flaccida
• II. Middle Ear Cavity
• ossicles and their ligaments
• m.e. muscles and their tendons
• eustachian tube

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Ossicles

• Malleus
• Manubrium
• Incus
• Short Process
• Long Process
• Stapes
• Neck
• 2 Crura
• Footplate

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Middle Ear Muscles

• Stapedius/Stapedial
• Inserts at neck of Stapes
• Tensor Tympani
• Inserts at the top of the manubrium of the malleus

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Eustachian Tube

• Resting State
• Drain Middle Ear fluid
• Helps equalize head pressure with atmospheric
  pressure

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Middle Ear Physiology

• Transducer
• Converts one form of energy to the other.
• Acoustic energy into mechanical energy.
• Transformer
• Voltage regulator
• Impedance Matching
• Resistance or opposition to energy flow.
• 35dB Impedance mismatch

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ME Transformer3 Components

• Areal Ratio
• The ratio of the effective area of the TM to the
  area of the stapes footplate.
• Ossicular Lever Effect
• Displacement of the longer manubrium of the
  malleus compared to the long process of the
  incus.
• Curved Membrane Principal
• The entire TM moves on both sides of the
  manubrium transferring a lot of force to the
  manubrium which transfers the same amount of
  force to the incus and the stapes to result in an
  increase in pressure at the stapes footplate.

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Inner Ear

• I-Osseous Labyrinth
• - Perilymph fluid
• - Vestibule
• - Cochlea
• - Semi-Circular Canals
• II-Membranous Labyrinth
• - Endolymph fluid

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Cochlea

• 3 Chambers
• 1. Scala vestibuli
• 2. Scala media
• 3. Scala tympani
• Reissners Membrane
• Basilar Membrane
• Organ of Corti
• Round window

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3 Chambers
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Cochlear Physiology

• Basilar Membrane Movement
• Traveling Wave Theory
• http//hypephysics.phy-astr.gsu.edu/hbase/sound/pl
  ace.html
• Hair Cell Stimulation
• Inner Hair Cells
• Outer Hair Cells
• Ryals, B.M. (2000). Hair cell regeneration
  revisited Its not just for the birds. The
  Hearing Journal. 53(8), 10-20.

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Hair Cell Regeneration Revisited Its not just
for the birdsRyals, B.M. (2000). Hair cell
regeneration revisited Its not just for the
birds. The Hearing Journal. 53(8), 10-20.

• Birds regenerate damaged and dead hair cells
• Research is now being done to determine if it is
  possible to regrow hair cells in mammals
• 3 major approaches to studying hair cell
  regeneration include
• - identifying cellular and molecular events that
  produce hair cell regeneration in birds
• - determining if hair cell regeneration can be
  induced in mammals by including molecules known
  to stimulate cell division in other tissues of
  the body
• - identify genes that may inhibit cell division
  in the inner ear, thereby preventing the first
  steps toward hair cell regeneration

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Study Conclusions

• After a new hair cell is regenerated it must be
  able to be stimulated and be able to transmit its
  signal to the brain
• Within 5-10 years- we will know if it is possible
  to regenerate hair cells in mammals
• From there it could be another 10 years until
  hair cell regeneration is achieved in humans

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Sensorineural LossKillion, M.C. (2000). What can
the pure-tone audiogram tell us about a patients
SNR loss?The Hearing Journal, 53(3), 47.
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Visual of Sensorineural LossKillion, M. C.
(2000). What can the pure-tone audiogram tell us
about a patients SNR loss? The Hearing Journal,
53(3), 46.
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Traveling Wave Theory

• Frequency is coded by place in the cochlea.
• Gradation of stiffness
• www.blackwellscience.com/matthews/ear.html

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Neurology of Hearing

• Internal Auditory Meatus
• Cerebellopontine Angle
• Central Auditory Nervous System(CANS)
• Cochlear Nucleus
• Superior Olivary Complex
• Lateral Lemniscus
• Inferior Colliculus
• Medial Geniclate Body
• Primary Auditory Cortex (PAC)

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CANSYost, W. and Donald Nielson. (1997). Highly
schematic diagram of the bilateral central
auditory system. Fundamentals of Hearing.p97.
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Pure Tone vs. Complex Sound

• A pure tone is a sound that consists of one
  single frequency. The sound wave, if recorded,
  would be a perfect sine pattern that repeated
  over and over with a given repetition rate.
• -William Roberston, Ph.D.
• Two or more pure tones are combined that
  repeat themselves over time.
• -Stanley A. Gelfand, Ph.D.
• http//physics.mtsu.edu/wmr/purecomp/html

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Characteristics of Sound

• Amplitude- demonstrates size of magnitude amount
  of displacement, power, pressure.
• Frequency- number of cycles that occur in one
  second.
• Cycle- one complete replication of a vibratory
  pattern.
• Phase- shows relationship between two waves that
  are displaced relative to each other.
• Quality-how energy is distributed over our speech
  frequencies.
• Resonant Frequency- increase in amplitude at
  certain frequencies.
• Damping-decrease in amplitude
• Breathy- turbulent noise which is made up of
  higher frequencies.
• Harsh- complex aperiodic sound
• Hoarse- a combination of Breathy and Harsh high
  frequency complex aperiodic sound.

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Measurement of Hearing

• Pure Tone Air Conduction
• www.handtronix.com/webdata/flash/onlinescreener.ht
  m
• OE, ME, IE
• Pure Tone Bone Conduction
• Best Cochlea
• Type of Hearing Loss
• Speech Threshold Testing
• Speech Detection Threshold
• Speech Recognition Threshold (SRT)

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Types of Hearing Loss

• Conductive
• Case History Clues
• Air Bone Gap-10dB difference
• Sensorineural
• Case History Clues
• AC and BC are out of normal range no ABG
• Mixed
• Case History Clues
• AC and BC are out of normal range and ABG!!!

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Pathologies of the Hearing Mechanism

• Otitis Media
• Otosclerosis
• Ossicular Disconnection

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Otitis Media

• Inflammation in the Middle Ear associated with
  fluid build up.
• Questions and Answers about Otitis Media,
  Hearing and Language Development. Retrieved
  September 27, 2002, from ASHA. Web site
  www.kidsource.com/ASHA/otitis.html
• Causes Conductive Loss
• Types
• Secretory
• Serous
• Acute
• Chronic

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Secretory Otitis MediaAKA blue ear

• ME infection of long duration that continues to
  be treated with antibiotics, but continues to
  come back.
• Fluid-(sterile) straw colored mucoid
• Treatment myringotomy with PE tubes

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Serous Otitis Media

• Originates from an upper respiratory infection.
• Fluid-(sterile) pale yellow color
• Treatment-antibiotics, tubes, decongestants,
  surgery or do nothing

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Acute Otitis Media

• True ear infection that comes on suddenly with
  severe pain. Ear drum may burst and leak fluid.
• Fluid- puss like purulent called otorrhea
• Treatment- myringotomy because of pain
• - antibiotics

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Chronic Otitis Media

• Caused by an infection that goes untreated for
  many months.
• Fluid- puss like purulent
• Treatment- usually antibiotics and tubes
  immediately depending on severity.

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Otosclerosiswww.american-hearing.org/name/otoscle
rosis.html

• Hardening of the Ossicles.
• Bilateral Conductive loss
• Range of loss
• www.ghorayeb.com/Otosclerosis.html

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Patients Perceived Outcomes After Stapedectomy
for Otosclerosis.Meyer, S.E. and C.A. Megerian.
(2000). ENT Ear, Nose, Throat Journal. 79(11)
846.

• Purpose Determine benefits of adding a
  self-evaluation to the customary postoperative
  audiometric test battery.
• Method
• 29 (74) consecutive patients with otosclerosis
• Same surgeon, procedure and materials
• Mean age 47 years. (Range 31-70 years)
• Between 8 weeks and 3 years after surgery.
• Pre and Postoperative perceptual surveys (HDHS)
  concerning patients ability to hear speech and
  nonspeech sounds, and the patients self-worth
  and quality of life while unaided.

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Average Patient Results

• I had forgotten little sounds like dripping
  water or mosquitoes buzzing
• Average degree of hearing impairment improved
  from moderately severe preoperatively to mild
  postoperatively.
• HDHS scores improved although postoperative score
  did not indicate the complete absence of any
  self-perceived disabilities or handicaps.
• Nonspeech sounds are slightly better than speech
  sounds but both improved.
• Hearing handicap less acute than hearing
  disability.
• Of the five patients who wore one hearing aid and
  six who wore two hearing aids, only three still
  use one aid and one uses two.

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Study Conclusions

• Patients perceptions do not correlate highly
  with audiometric data.
• Retrospective nature of rating scale used
• Reliance on patients memory
• Patient postoperative experiences
• Patient personality and expectations.
• Scores can help identify patients who may
  benefit from additional counseling or aural
  rehabilitation.
• Patients whos audiometric score shows major
  improvement but do not perceive a difference.

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Causes and Treatment

• Inherited
• Viral
• Nothing
• Amplification
• Medical
• Surgical-Stapedectomy

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Ossicular Disconnections

• Interruptions in the ossicular chain.
• Conductive Loss
• www.ghorayeb.com/OSSICULARRECONSTRUCTION.html