Lecture 22: Hearing Assessment and Diagnosis Management of Hearing Impairment Flashcards
Conductive hearing loss is due to ___________\_
Sensorineural hearing loss is due to___________
Central deafness, auditory processing disorders is due to __________\_
Conductive hearing loss is due to outer and middle ear disease (loss of sound transduction from outside to ear)
Sensorineural hearing loss is due to inner ear disease (e.g. damage to neurons or sensory hair cells)
Central deafness, auditory processing disorders is due to abnormal central processing
How would someone with Conductive hearing loss perceive sound and how would someone with sensorineural hearing loss perceive sound?
Conductive hearing loss symptoms include sounds muffled/dull (decreased volume), may have tinnitus
Sensorineural hearing loss symptoms include poor discrimination of frequency/speech, distortion, l_oudness imbalance_, different frequencies missing, tinnitus.
What are some causes of Conductive Hearing loss?
- Congenital disorders (cranial/facial malformation)
- Outer ear and middle ear infections (especially children, e.g. glue ear)
- Cholesteatoma (benign epithelial tumour in middle ear, often due to chronic infection)
- Ossicular chain fixation (otosclerosis)
- Trauma
- Tumours
What is the name of this disease:
epithelial tissue growing behind ear drum (internalising).
Cholesteatoma (cholesterol-containing granulation tumor) is due to epithelial tissue growing behind ear drum (internalising). It is a corrosive tumour that can erode middle ear bones and possibly brain infection.
What is cholesteatoma?
Cholesteatoma (cholesterol-containing granulation tumor) is due to epithelial tissue growing behind ear drum (internalising). It is a corrosive tumour that can erode middle ear bones and possibly brain infection.
What are some causes of sensorineural hearing loss?
Mostly sensorineural hearing loss is due to damage or loss of sensory cells and nerve fibres in the cochlea
- Congenital disorders (inner ear)
- Inner ear infections (labyrinthitis)
- Ototoxic drugs (kills sensory hair cells, e.g. aspirin, diuretics)
- Inner ear fluid disturbances (e.g. Ménières disease)
- Trauma
- Noise exposure
- Age-related (elderly)
What are some causes of Central Auditory Disorders?
Causes Of Central Auditory Disorders
Central auditory disorders in processing sound in the brain include:
- Auditory processing disorders, auditory neuropathy spectrum disorder (children),
- Amblyaudia (lazy ear),
- Hyperacusis (hypersensitity to sound) (loss of relationship between PNS and CNS, disturbed feedback loop)
- Tinnitus
What are the 3 overall types of hearing assessments?
1) Behavioural e.g. audiometry
2) Physiological e.g. middle ear assessment
3) Functional imaging
Describe the 2 types of Beahvioural assessment of hearing
- Audiometry: Pure-Tone Air And Bone Conduction, Speech
Assessment
Clinicians measure s_ound intensity in dB HL (decibels hearing level)_, i.e. dB relative to the quietest sounds that a young healthy individual ought to be able to hear. Thresholds between -10 and +20 dB HL are considered in the normal range.
Pure-Tone Air And Bone Conduction Audiometry
- Headphones for air conduction
- Bone vibrator for bone conduction
Pure-Tone Air And Bone Conduction* *Audiogram
- Graph of threshold ability of the individual to hear different frequencies. (see pic)
- The left graph suggests that hearing loss occurs on high frequencies (problem with inner ear?)
- The right graph suggests that hearing loss is consistent across all frequencies, but when using a bone conductor, hearing level is okay, so perhaps there is an issue with the middle ear, not inner ear? (Bone conductor by-passes middle ear)
Speech Audiometry
Speech tests assess comprehension and detection of speech (e.g. “repeat after me”)
- Speech detection thresholds
- Speech detection in background noise (e.g. fine when alone, but cannot hear with background noise)
- Discrimination of speech (words, sentences)
- Age appropriate tests
- Behavioural Audiology in Children: Paediatric Audiology
Specialised behavioural testing of infants and young children. Complex. Possible beyond 4 months.
- Behavioural observation audiometry (4-8 months)
- Visual reinforcement audiometry (8 months to 2 years)
- Play audiometry (2-5 years)
- Standard pure-tone audiometry (over 5 years)
Describe the 4 Physiological assessments of hearing
1) Middle Ear Assessment: Tympanometry
Assessment
Probe into ear canal to measure pressure, also play pure tone sound to measure how much pass through middle ear (into inner ear).
The instrument changes the pressure in the ear, generates a pure tone, and measures the eardrum responses to the sound at different pressures. This produces a series of data measuring how admittance varies with pressure, which is plotted as a tympanogram.
Tympanometry assesses:
- Ear drum mobility (e.g. glue ear)
- Middle ear pressure
- Integrity of middle ear muscles and related neural pathways
Graph:
Type B has no mobility, fluid behind eardrum (no equalised pressure at all)
Type C has high negative pressure in middle ear (eardrum too stretched, probably Eustachian tube problem)
2) Electrodes (?)
- Observe the neural activity of cochlea and auditory brain centres (e.g. deliver a ‘bee’ and look for a peak’
- Helpful in people where no behavioural measures can be done
- Auditory brainstem response or cortical potentials can be used to obtain “hearing thresholds”
—–Early detection of hearing loss in babies (newborn hearing screening)—-
3) Otoacoustic Emissions
- Otoacoustic emissions measure sounds generated by outer hair cells (due to its vibrations stimulated by soft sound) in cochlea. (this way you can check if the ear is working- you cannot say if the child is hearing)
- Low frequencies are at apex so takes longer to travel. High frequencies are at base so shorter travel distance.
4) Automated Auditory Brainstem Response
Auditory Brainstem Response (ABR) could test of integrity of cochlea and brainstem.
- ABR or cortical potentials are useful to get hearing thresholds (e.g. can assess presence of eighth nerve tumours).
- Can be used as a neonate screening test.
What are some Interventions for Congenital Hearing Loss in Babies
- Auditory/verbal (hearing instruments/aids, cochlear implants)
- Sign language
Describe the Management of Hearing Loss
Developments in Technology: Devices
Introduction
Early detection and treatment essential!
- Hearing aids and implantable hearing aids (battery requirement)
- Cochlear implants (no battery required due to induction coil)
- Brain implants (cochlear nucleus)
Briefly describe cochlear implants
Cochlear Implant (Bionic Ear)
- Cocholear implant bypasses sensory cells to stimulate nerve directly. There are 22 electrodes to stimulate particular frequencies to treat people without sensory cells. Over 300,000 fitted worldwide, 100+ in New Zealand annually.
- Very successful for very young children and adults who have good language.
- Children have a critical period which starts to close after 5+ years (before auditory cortex gets taken over by visual cortex)
- Followed by intensive (re)habilitation
What are some prevention strategies for Hearing impairment?
1) Immunisation
2) Avoidance of ototoxic drugs (e.g. aminoglyoside antibiotics)
3) Noise (about 25% hearing loss)
