Transcript Audiology 3 File

AUDIOLOGY 03
Hearing assessment & the vestibular
organ
based on Adam Beckman’s* lecture 2015
*Head of Audiology Services, Plymouth Hospitals NHS trust
Pedro Amarante Andrade, PhD
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BIOSCIENCES
FOR SPEECH AND LANGUAGE THERAPY
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INTRODUCTION
• Physics of sound
• The ear (Anatomy and Physiology)
• Hearing
– How it works
– How we measure it
– Pathology
• The vestibular system
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INTRODUCTION
• The Ear
• with reference to acoustics, anatomy and physiology
– What goes wrong – pathology
– How we test hearing and function
• Year 2
– More detail in paediatrics
• Year 3
– Adult acquired loss and its amelioration
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HEARING LOSS STATISTICS
• There are more than 10,000,000 in the UK with some
form of hearing loss, or 1/6 of the population.
• From the total 3.7 million are of working age (16 –
64) and 6.3 million are of retirement age (65+).
• By 2031, it is estimated that there will be 14.5
million people with hearing loss in the UK.
• More than 800,000 people in the UK are severely or
profoundly deaf.
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HEARING LOSS STATISTICS
• About 2 million people in the UK have hearing aids, but
only 1.4 million use them regularly.
• At least 4 million people who don't have hearing aids
would benefit from using them.
• On average it takes ten years for people to address their
hearing loss.
• About one in ten adults in the UK have mild tinnitus and
up to 1% have tinnitus that affects their quality of
life.
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HEARING LOSS STATISTICS
• There are more than 45,000 deaf children in the UK,
plus many more who experience temporary hearing
loss.
• More than 70% of over 70 year-olds and 40% of
over 50 year-olds have some form of hearing loss.
• There are approximately 356,000 people with
combined visual and hearing impairment in the UK.
Action on Hearing Loss
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ASSESSMENT OF HEARING
• Aim
– to measure the quietest sound that person can
hear at different frequencies and plot an
audiogram for each ear
• And
– to establish where in the auditory pathway the
problem lies i.e. type of hearing loss
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HEARING LOSS DESCRIPTORS
• Degree of hearing loss
– How bad is it?
• Site of hearing loss
– Where in the system is it?
• High frequency speech sounds?
– Consonants
• “s”, “t” etc
• Low frequency speech sounds?
– Vowels
• “oo”, “aa”
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DEGREES OF HEARING
LOSS
http://medicalaudiology.com.au/adult-hearing-assessments/
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DEGREES OF HEARING
LOSS
Normal
conversation
level
Right Ear (red circle)
Left Ear (blue x)
http://www.audina.net/en/content/view?id=11
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TYPES OF HEARING LOSS
• Conductive
– outer ear
– middle ear
• Sensori-neural
– cochlea (sensory)
– auditory nerve (neural)
• Mixed
• Central
– Not considered today
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SOME FACTS ABOUT HEARING
LOSS
•
•
•
•
Bilateral or Unilateral
Symmetrical or Asymmetrical
Can affect both ears in varying degrees
Hearing results (Audiogram) does not indicate
degree of disability
• Patient can have more than one type of hearing
problem
• Hearing results can change
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MEASURING HEARING FUNCTION
Two basic tests:
– Pure tone audiometry
– Tympanometry
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PURE TONE AUDIOMETRY
• What is it?
– Measure of hearing threshold, using air or bone
conduction (across the normal speech
frequencies)
• How is threshold defined?
– Psychometrically, based on method
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PURE TONE AUDIOMETRY
• Method
– Instruct patient
– Remove obstructions
• Examples…
– Estimate hearing
• How?
– Ask for better hearing ear
– Place headphones
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PURE TONE AUDIOMETRY
• Method
– Start with better ear
• 1 kHz, 1-3 sec
• 30dBHL above ‘threshold’
• Reduce intensity by 10dBHL
– Until no response
• Increase by 5dBHL
– Until response
• Reduce by 10, increase by 5
• Until:
– 2 responses out of 2
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PURE TONE AUDIOMETRY
• Method
– i.e. Threshold is defined as level at which patient
responds at least 50% of time on ascending
presentations (for clinical purposes)
– Start at 1kHz
– Repeat at 2, 4, 8, 0.5 & 0.25 kHz
– Repeat 1 kHz
– Test other ear
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PURE TONE AUDIOMETRY
• Presentation – beware
– Rhythm
– Visual cues
– Auditory cues
– Unreliable responses
• Non-organic
• Tinnitus
– Fatigue
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PURE TONE AUDIOMETRY
• Method
– Test bone conduction
•
•
•
•
Remove obstructions
Order: 1, 2, 4, 0.5 kHz
Why not 8 kHz
Why not 0.25 kHz
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PURE TONE AUDIOMETRY
• Masking
– Why?
– When?
– How?
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PURE TONE AUDIOMETRY
• Masking
– Why?
• Sound can cross over to other cochlea
– Ensure know which ear is hearing
– When?
• 40dB or greater difference in AC thresholds
• 10dB or more air-bone gap
• 40dB or greater gap between AC test ear and BC nontest ear
– How?
• Narrow band noise applied to the other ear
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PURE TONE AUDIOMETRY
Degree of hearing loss
• Basic classification
– Mild
• >20 and ≤40dBHL
– Moderate
• >40 and ≤60dBHL
– Severe
• >60 and ≤90dBHL
– Profound
• >90dBHL
http://medicalaudiology.com.au/adult-hearing-assessments/
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Walker et all, 2013. Audiometry screening and interpretation. Am
Fam Physician. Jan 1;87(1):41-47.
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Walker et all, 2013. Audiometry screening and interpretation. Am
Fam Physician. Jan 1;87(1):41-47.
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Walker et all, 2013. Audiometry screening and interpretation. Am
Fam Physician. Jan 1;87(1):41-47.
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Walker et all, 2013. Audiometry screening and interpretation. Am
Fam Physician. Jan 1;87(1):41-47.
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MEASURING HEARING FUNCTION
Two basic tests:
– Pure tone audiometry
– Tympanometry
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TYMPANOMETRY
• Why?
– TM most flaccid when pressure in External
Auditory Meatus equals pressure in Middle Ear
– Most sound transmitted when Tympanic
Membrane is most flaccid
• How?
– Apply sound of known level
–226 Hz @ 85dBSPL
• Measure reflected sound using pressure
gradient
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TYMPANOMETRY
Measures three factors:
Size of ear canal
cm3
Middle ear pressure
daPa
Maximum compliance
cm3
https://commons.wikimedia.org/wiki/File:Tympanometry.svg. Scott Martin
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NORMAL TYMPANOMETRY
www.aafp.org
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• A - Normal
Overly Flexible
• As - Otosclerosis or
ossicular fixation
• AD - Ossicular
discontinuity
• C - Eustachian tube
dysfunction
• B - Middle ear
atelectasis (the TM is
rigidly fixed to the
middle ear) or otitis
Inflexible
media with effusion
http://www.vrab-tacra.gc.ca/
Glue ear, wax blockage or (glue ear)
perforation
TM pushed out
TM sucked in
DIFFERENT TYMPANOMETRY
RESULTS
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HEARING LOSS
CAUSES
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CONDUCTIVE HEARING LOSS
Outer ear
– Congenital malformation
• e.g. atresia, microtia
• Gain none of the benefits of
– Pinna, ear canal, ear
drum
• Sound transmitted via bone
conduction only to inner
ear
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AUDIOMETRY - TYMPANOMETRY
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CONDUCTIVE HEARING LOSS
Outer ear
– Blockage
• Wax
• Infection
• Foreign body
Sound transmission attenuated
by blockage
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CONDUCTIVE HEARING LOSS
• Outer ear
– Exostosis
• “Surfer’s ear”
– Mild
• Little effect on hearing
• But trapped water and wax
 more prone to infection
– Severe
• Lose benefits of ear canal
resonance (attenuates sound)
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CONDUCTIVE HEARING LOSS
• Outer ear
– Perforation
• Small – mild hearing loss
–Ear drum still works
» Vibrates sounds, passes to ossicles
» Smaller surface area
» Less elastic
–More prone to infections
• Large – moderate hearing loss
– Greater reduction in surface area
– Does not vibrate ossicles well
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CONDUCTIVE HEARING LOSS
• Middle ear
– Eustachian tube dysfunction
• Blocked Eustachian tube
• Negative pressure in middle
ear
• TM “sucked in”
–Less mobile
–Sound not transmitted
through as well
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CONDUCTIVE HEARING LOSS
• Middle ear
– Otitis media with effusion/glue
ear
• Eustachian tube blocked
• Build up of fluid in middle ear
• Sound not transmitted
though well
• Normally mild hearing loss
–Can be moderate
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CONDUCTIVE HEARING LOSS
• Middle ear
– Infection
• Fluid in middle ear
• Acute infection
–Build up of pressure
–Painful +++
http://otitismedia.hawkelibrary.com/
• Discharge if ear drum
perforates
http://know-your-body.wonderhowto.com
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CONDUCTIVE HEARING LOSS
• Middle ear
– Cholesteatoma
• Build up of debris in middle ear
– Grows slowly
– Erodes ossicles, skull
– Needs to be surgically removed
– Otosclerosis
• Bony growth on ossicles
– Normally footplate of stapes
• Reduces movement of ossicles
– Sound transmission to cochlea reduced
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CONDUCTIVE HEARING LOSS
• Middle ear
– Tympanosclerosis
• Scarring on ear drum
• Collagen deposition - plaques
– Does not transmit sound as well
– Ossicular malformation
• Congenital
• Ossicles do not transmit sound through as well
– Ossicular fracture or discontinuity
• Ossicles do not transmit sound through as well
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SENSORI-NEURAL HEARING LOSS
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SENSORI-NEURAL HEARING LOSS
• Inner ear/nerve
• What can go wrong?
– Outer hair cells
– Inner hair cells
– Cochlear fluids
– Neural transmission
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SENSORI-NEURAL HEARING LOSS
• What are the causes?
– Congenital
• Syndromic
• Non-syndromic
– Infections
• Prenatal
• Postnatal
–
–
–
–
Trauma
Ototoxicity
Noise induced
Ageing
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EXAMPLES OF SYNDROMIC CAUSES
Recessive
syndromes
Dominant
syndromes
X-linked
syndromes
Chromosomal
disorders
•Usher’s
Waardenburg
Alport’s
Down
Syndrome
Syndrome
Syndrome
Syndrome
•Pendred’s
Treacher Collins
Hunter
Turner
Syndrome
Syndrome
Syndrome
Syndrome
• Can effect different parts of the inner ear
• Over 3000 – many rare problems can now be identified via genetic
testing
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NON-SYNDROMIC
• Genetic sensorineural hearing loss
– Connexin 26
• Most common
– Mitochondrial
Connexin 26 (Cx26) is a protein
found on the (GJB2) gene and is
the most common cause of
congenital sensorineural hearing
loss
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PRENATAL INFECTIONS
• STORCH
– Syphilis
– Toxoplasmosis
– Rubella
– Cytomegalovirus
– Herpes
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PERINATAL PROBLEMS
– Anoxia at birth
– Assisted ventilation
– Jaundice
– Low birth weight
– Mainly hair cell damage, but can effect
other parts of the system as well
• Including neural problems
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POSTNATAL INFECTIONS
– Bacterial Meningitis
– Meningococcal septicaemia
– Mumps
– Measles
– Scarlet fever
– Mainly hair cell damage
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TRAUMATIC
• Skull fracture (temporal bone)
– Can cause loss of fluids from cochlea
• Acoustic trauma
– explosions, fireworks, gunfire, rock concerts, and
earphones
– Can cause damage to:
• Ear drum, hair cells, cochlear fluids
• Barotrauma (differences in pressure)
– Diving
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• Aminoglycoside antibiotics
OTOTOXICITY
– Gentamicin etc
• Aspirin
– large doses
• Chloroquine (Antimalarial medications)
– Quinine and derivatives
• Chemotherapy
– E.g. cistplatin
• Mainly hair cell damage
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NOISE INDUCED - PROLONGED
EXPOSURE
• Leisure noise
– Increasing
• Increased levels at concerts/clubs
• Personal listening devices
• Industrial noise
– Reducing
• Noise at work regulations
• Mainly outer hair cell damage
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SENSORINEURAL LOSSES - OTHER
CAUSES
• Age-related hearing loss
– Most common
– Variety of potential changes with time
•
•
•
•
Outer hair cell
Inner hair cell
Electrolyte imbalance
Neural conduction
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SENSORINEURAL LOSSES - OTHER
CAUSES
• Meniere’s disease
– Associated with dizziness and tinnitus
– Fluctuating symptoms
– Problem with cochlear fluids
• Infection
– Inner ear
• Ischaemia
– Loss of blood supply
– Hair cell damage
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NEURAL HEARING LOSSES
• Acoustic Neuroma
– Growth on the VIII Nerve
• Multiple Sclerosis
• Neurodegenerative disorders
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EFFECT OF HEARING LOSS
• Depends on
– Age of onset
– Degree of loss
• Will be covered in years 2 and 3
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SUMMARY
• Many conditions can effect hearing
– Outer, middle or inner ear
– VIII nerve
• Basic tests will identify
– If hearing loss is conductive or sensorineural
– Likely cause of conductive losses
• These provide that start of developing the
appropriate management
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REFERENCES
• Gelfand (2004) Hearing. An introduction to psychological and physiological
acoustics (4th Ed) Chapter 4. Cochlear mechanisms and processes (p121177)
• Katz (2002) Handbook of Clinical Audiology (5th Ed)
• Moore (2003) An introduction to the psychology of hearing (5th Ed).
Chapter 1: The nature of sound and the structure and function of the
auditory system (p 1-54)
• Lectures compiled from lectures provided by the Audiology team at QMU
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AUDIOLOGY 03
The vestibular organ
based on Adam Beckman’s* lecture 2015
*Head of Audiology Services, Plymouth Hospitals NHS trust
Pedro Amarante Andrade, PhD
LCSC06
BIOSCIENCES
FOR SPEECH AND LANGUAGE THERAPY
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THE VESTIBULAR SYSTEM
Blausen.com staff. "Blausen gallery 2014". Wikiversity Journal of Medicine. DOI:10.15347/wjm/2014.010. ISSN
20018762. - Own work. Licensed under CC BY 3.0 via Wikimedia
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THE VESTIBULAR SYSTEM
"Sobo 1911 773" by Dr. Johannes Sobotta - Sobotta's Atlas and Text-book of Human Anatomy 1911. Licensed under Public
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THE VESTIBULAR SYSTEM
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SEMI-CIRCULAR CANALS
• 3 canals orthogonally (at right angles) to each
other
– Horizontal or lateral semi-circular canal
– Superior or anterior semi-circular canal
– Posterior semi-circular canal
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SEMI-CIRCULAR CANALS
• Filled with endolymph
• End open up into bulge
– Osseous ampulla
– Inside this is the crista ampullaris
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SEMI-CIRCULAR CANALS
"Vestibular system's semicircular canal- a cross-section" by United States government - http://www.cami.jccbi.gov/aam400/phys_intro.htm.. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/
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SEMI-CIRCULAR CANALS
• Rotational movement
– Displaces hair cells
• Semi-circular canals in action
• Push-pull system
– Left and right
– Excitatory on one side = inhibitory on the other
side
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SEMI-CIRCULAR CANALS
• Horizontal or lateral semi-circular canal
– 12-15mm long
– Arched horizontally – laterally and backwards
– Head rotating sideways
• E.g. “No”, crossing road
• Superior or anterior semi-circular canal
– 15-20mm long
– Arched upwards
– Head rotating front-back
• E.g. nodding “yes”
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SEMI-CIRCULAR CANALS
• Posterior semi-circular canal
– 18-22mm long
– Arched upwards at the back
– Rotation
• Head tilting onto shoulder
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SEMI-CIRCULAR CANALS
• Movement stops
– Endolymph continues to move
• Lag
• Endolymph moving
• Continuous movement
– Habituates
• No longer aware turning
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OTOLITH ORGANS
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OTOLITH ORGANS
• Utricle and saccule
• Sensitive to
– Linear acceleration
– Gravity
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OTOLITH ORGANS
"Bigotolith" by Original uploader was Password
at en.wikipedia - Transferred from en.wikipedia;
Transfer was stated to be made by
User:Padawane.. Licensed under Public Domain
via Wikimedia Commons http://commons.wikimedia.org/wiki/
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OTOLITH ORGANS
• Endolymph
• Hair cells
• Otoliths
– Calcium carbonate crystals in gelatinous material
• Change of direction of force
– Otoliths move, shearing motion on hair cells
• Otolith video
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OTOLITH ORGANS
• Utricle
– Larger otolith organ
– Linear acceleration
• Start in a car
– Crystals have more mass
– Take longer to start moving – drag the stereocilia
• Stop in a car
– Crystals have intertia
– Continue to move – drag the stereocilia in the opposite
direction
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OTOLITH ORGANS
• Saccule
– Smaller otolith organ
– Vertical acceleration
• Gravity
• Going up or down in a lift
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OTOLITH ORGANS
• Information utilised from
– Left and right organs
– Proprioception
• Neck
– Eyes
– example;
• Tilt head backwards
– Is head tilting or body tilting?
– We know head is tilting from combined information from neck
and otolith organs
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VESTIBULO-OCULAR REFLEX
• When we walk, why doesn’t this happen?
• Film trailer.....
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VESTIBULO-OCULAR REFLEX
• Steadicam
• Tracking shot with steadicam......
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VESTIBULO-OCULAR REFLEX
• Image stabilised on retina
• When head moves, eyes move in opposite
direction
– Head move right, eyes move left and vice versa
• Head moving all the time
– So essential
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VESTIBULO-OCULAR
REFLEX
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VOR – ROTATION TO THE LEFT
• Movement of endolymph in semi-circular
canal
– Signal to:
• VIII nerve
• Nucleus vestibularis
• Contralateral VI nerve
– Nucleus abducens
• Lateral rectus AND also medial longitudinal fasciculus of
contraleteral eye
• Medial rectus muscle of each eye
• Eyes move to the right
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VESTIBULO-OCULAR REFLEX
• Problems with VOR will make everyday
activities challenging
– Reading
– Driving
– Walking down stairs
– ………..
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SUMMARY
• Summary video
• Vestibular system
– Semi-circular canals
– Otolith organs
– Vestibulo-ocular reflex (VOR)
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