Lecture 2 Flashcards
List signs of hearing loss
- People around you seem to mumble.
- You can hear, but cannot understand.
- Need to turn up the TV or radio louder.
- Difficulty following conversation sin background noise or when in groups – this is because background noise is low frequency and therefore people with a high-frequency hearing loss can only hear the background.
- Cannot hear high-pitched sounds: e.g. birds, crickets and bells.
- You often ask others to repeat themselves.
- Children and women’s voices are difficult to hear (because F0 is higher).
Why is hearing loss is associated with the cognitive decline, fall risk, hospitalisations, and global burden of disease that is frequently experienced by the ELDERLY?
Because those with a hearing loss have limited cognitive and attentional resources (cognitive load becomes too high when other tasks are involved).
What is the difference between a hearing screening and a full audiological assessment?
Hearing screening = audiometric test, whereby a criterion level (in dB) is specified for different frequencies. Individuals who respond at this level pass the test, and individuals who do not respond at this level fail the test.
Audiological assessment is performed AFTER a hearing screening by an AUDIOLOGIST to give a differential diagnosis.
What are the criterion levels for
- Children
- Adults
For children, a score >20dBHL suggests the child is “at risk” for speech, language, educational and psychological difficulties.
For adults, a score of 25dB is acceptable.
What is HL?
Sound loudness is measured in Sound Pressure Level (SPL) or Hearing Level (HL). HL is the “adjusted” level according to people with normal hearing. HL is the unit most often used when defining hearing levels.
What are the three main parts of the ear?
Outer ear, middle ear, inner ear
What does the outer ear consist of? What is the role of each part?
- Pinna: funnels sounds toward inner ear (shape reflects function)
- Ear canal (external auditory meatus): sound waves travel down the ear canal and hit the ear drum
- Ear drum (tympanic membrane): curved, sound wave causes it to vibrate and it passes on the sound
What does the middle ear consist of? What is the role of each part?
- Ossicles: three small bones (malleus, incus and stapes) that pass on the sound wave after it has travelled through the tympanic membrane. They function to amplify sound waves by around 30dBSPL.
- Eustachian tube: links to the back of the throat and the nose (nasopharynx); drains fluid/mucus from middle ear → nasopharynx
- Equalises pressure in middle ear when open
- Eustachian tube closes up as a protection mechanism when pressure changes in a plane etc.; we try and open up the Eustachian tube again by chewing/swallowing
What does the inner ear consist of? What is the role of each part?
- Semicircular canals: responsible for balance
- Cochlea: the organ responsible for hearing; the cochlea is filled with fluid which moves in response to incoming vibrations.
- Contains thousands of hair cells which convert this motion into an electrical signal, which is communicated to the brain via the cochlear nerve.
The basiler membrane is located within the cochlea. What does it contain and what is its role?
- Bends in response to incoming waves of any frequency
- Contains the hair cells that transform the sound signal from a physical one to an electrical one (Organ of Corti)
- High frequency sounds cause more vibration in the base of the membrane; low frequency = apex of membrane
What are the three types of hearing loss? (x3)
- Conductive
- Sensorineural
- Mixed
What are the symptoms, causes, and solutions for conductive hearing loss?
Symptoms:
• Sound is blocked in the outer or middle ear.
Causes:
• Excessive earwax
• Damaged eardrum
• Ear infection or fluid in the
middle ear
• Stiffness in the bones of the
middle ear (otosclerosis)
Solutions:
• Most often medically treated with high success rates
• Hearing aids very successful if unable to treat medically.
What are the symptoms, causes, and solutions for sensorineural hearing loss?
Symptoms:
• Inner ear hair cells or hearing nerve is damaged and cannot send complete signals to
the brain.
Causes:
• Ageing
• Noise exposure
• Hereditary factors
Solutions:
• Cannot be corrected with medicine or surgery.
• Hearing aids can be very helpful.
• If severe to profound hearing loss, cochlear implants may be an option.
What are the symptoms, causes, and solutions for mixed hearing loss?
• Combination of conductive and sensorineural
Causes:
• Combination of factors that cause conductive and sensorineural losses
• Can be permanent or temporary.
Solutions:
• Depends on the causality of the mixed hearing loss.
• Hearing aids can be very helpful
• If severe to profound hearing loss, cochlear
implants or bone-anchored hearing aids may be an option.
What are the initial signs of noise-induced hearing loss?
o Tinnitus
o Things don’t sound clear after listening to loud music
o Headaches
What does it suggest if an audiogram displays a pattern of loss for air conduction but NOT bone conduction?
A CONDUCTIVE hearing loss.
Bone conduction measures the function of the cochlea (inner ear). Therefore, a normal pattern of bone conduction suggests good cochlea function (which therefore means that the hearing deficit must be occurring BEFORE sound reaches the cochlea (therefore must be in the middle/outer ear = conductive).
What does it suggest if an audiogram displays a similar pattern of loss for both air conduction and bone conduction?
A SENSORINEURAL hearing loss.
Bone conduction measures the function of the cochlea (inner ear). Therefore, a decrease in bone conduction suggests a deficit in cochlea function (or in the transmission of impulses from the cochlea through the auditory nerve).
What is a unilateral hearing loss? What would this look like on an audiogram?
A hearing loss (may be conductive or sensorineural) affecting only ONE ear. This appears as a NORMAL in one ear, and a DISORDERED pattern in the other ear).
What questions are useful to ask in a hearing screening case history?
- Have you had tinnitus (ringing in the ears)?
- Previous problems ‐ wax, infections, operations?
- Excessive noise exposure?
- Gradual, progressive or sudden onset of problems?
- Symmetrical or asymmetrical hearing?
- Reported communication difficulties ?
What is tympanometry?
A way of measuring the function of the OUTER and MIDDLE ear, including the VOLUME of the ear canal, the MOBILITY of the eardrum, the presence of FLUID in the middle ear (which would prevent sound from passing through). Tympanometry also tells us if there may be a perforation (hole) in the eardrum.
What does a tympanogram represent?
Maximum COMPLIANCE of the middle ear system (i.e. mobility of the whole system) occurs when the PRESSURE in the MIDDLE ear cavity is EQUAL to the pressure in the EXTERNAL auditory canal.
This suggests that there is nothing BLOCKING (and therefore increasing the PRESSURE of) the outer OR middle ear.
This compliance (static acoustic admittance) is represented by the highest peak of the curve on the graph. For a normal functioning ear, this peak should be at ZERO.
What does a Type A tympanogram look like? What does it represent?
A clear peak at approximately ZERO.
This represents NORMAL middle ear function - therefore could be reflective of normal hearing overall OR of a sensorineural loss.
What does a Type B tympanogram look like? What does it represent? What will the symptoms be?
Represents restricted tympanic mobilty (i.e. mobility of the eardrum).
Type B curves have little or no point of maximum mobility (i.e. NO PEAK).
This curve is very typical of a STIFF middle ear, typical of Otitis Media.
What does a Type C tympanogram look like? What does it represent?
Type C curves have a clear peak at LESS THAN ZERO.
This indicates a NEGATIVE PRESSURE (i.e. there is a significant difference in pressure between the outer and inner ear).
Mobility is generally OK.
