1: Hearing Loss Flashcards
What are the three types of hearing loss
- Sensorineural
- Conductive
- Mixed
What causes sensorineural hearing loss
Defect in inner ear or vestibulocochlear nerve
What causes conductive hearing loss
Defect in middle or outer ear
When does conductive hearing loss tend to present more
Children
Young Adults
When does sensorineural hearing loss tend to present
Middle-age
Older age
Give 5 causes of conducting hearing loss
- Otosclerosis
- Otitis media
- Barotrauma
- Cerumen impaction
- External auditory meatus atresia
What is cerumen impaction
Build-up of wax in the external auditory canal
What are 6 causes of sensorineural hearing loss
- Ototoxicity
- Meniere’s Disease
- Acoustic neuroma
- Presbycusis
- Inner ear infection (Mumps, measles, meningitis)
- Noise-induced hearing loss
Otosclerosis
Overgrowth of the stapes causing it to fix to the oval window
What is otitis media
Bacterial or viral infection of the middle-ear
What is barotrauma
Failure to equalise atmospheric pressure with the middle ear
How will otosclerosis present
Progressive conducting hearing loss. 70% develop it in the second ear.
What symptom is specific to otosclerosis
Paracusis Willisi
What is paracusis willisi
Patient’s hear better in noisy compared to quiet environments
What sign is seen on the tympanic membrane in otosclerosis
Schwartz sign
What is the schwartze sign
Red-blue tinge to tympanic membrane
In what age does otitis media present
6-24m following URTI
How will barotrauma to the ear present
sudden-onset stabbing pain in the ear. Tinnitus and hearing loss. Bleeding from the canal indicates perforation of the ear drum.
How does presbycusis present
High-frequency hearing loss
How does noise-induced hearing loss present
Gradual high-frequency hearing loss. Often unable to hear in noisy environments
How does meniere’s disease present
Episodes lasting to minutes-hours of:
- Vertigo (Horizontal Nystagmus)
- Sensorineural hearing loss
- Tinnitus
What nerves are affected initially in acoustic neuroma
- vestibular
- cochlear
What nerves are affected late in acoustic neuroma
- trigeminal
- facial
How will early symptoms of acoustic neuroma present
Vestibular - vertigo
Cochlear - unilateral tinnitus, hearing loss
How will late symptoms of acoustic neuroma present
Trigeminal - facial parasthesia
Facial - unilateral paralysis
Explain investigations in work-up of hearing loss
- Inspection
- Whispered hearing test
- Rinne’s
- Weber’s
- Otoscopy
- Pure tone audiometry
- Tympanometry
What is looked for when inspecting the ear in hearing loss
Otitis externa
Cerumen Impaction
What is the whispered voice test
Gross hearing assessment
Explain the whispered voice test
- Stand 60cm behind someones ear. Rub tragus in the ear not being tested.
- Whisper a number into the other ear.
- Repeat this 3-times. If the patient can hear in 2/3 it indicates their hearing is >12dB
In the whispered voice test, if having to use a conversational voice how many decibels can they hear
48db
In the whispered voice test, if having to use a loud voice how many decibels can they hear
72db
Explain weber’s test
Place a 512Hz tuning fork in the middle of the patient’s head and ask them where they hear it loudest
What is a mnemonic to remember results of weber’s test
SICA
In sensorineural hearing loss, where will the sound localise to
It would localise to the intact ear
In conductive hearing loss, where will the sound localise to
It would localise to the affected ear
What is a rinne’s positive test
When air conduction is better than bone conduction
What can cause a rinne’s positive test
- Normal
- Sensorineural hearing loss
What is a rinne’s negative test
Bone conduction > Air conduction
What causes a rinne’s negative test
Conductive hearing loss
Explain pure tone audiometry
- Patient is placed in a sound-proof room
- Head phones deliver sounds at increasing frequencies
- It is played initially above hearing threshold and increase in 10db increments until a 50% response rate is obtained
- Transducer can be used to obtain bone conduction
What goes on the X-axis in pure tone audiometry
Frequency (Hz)
What goes on the Y-axis in pure tone audiometry
Decibels
What is normal hearing range on audiometry
Anything above 20db
Explain conductive hearing loss on audiometry
Auditory threshold increased in air conduction, normal bone conduction
What does conductive hearing loss on audiometry indicate
Middle or external ear pathology
Explain presentation of otosclerosis on audiometry
- Air conduction is reduced
- Bone conduction shows a characteristic notch at 2,000Hz called cahart notch
Explain how presbycusis will present on audiometry
Decrease in air and bone conduction at higher frequencies
Explain how noise-induced hearing loss presents on audiometry
Decrease in noise and air conduction at 4,000Hz
What is tympanometry also referred to as
Acoustic impedance audiometry
What is tympanometry
Method to measure pressure in the middle-ear
Explain the procedure of tympanometry
- In a normal ear compliance of the ear drum (and hence amount of fluid in mL displaced for a particular sound) peaks when middle ear pressure equals canal pressure
- A probe with an air tight seal is put into the meatus - the amount of acoustic signal reflected back at points is used to generate a graph of compliance
What is a normal ear type on tympanometry
type A
What is type A
There will be a peak which will then decrease. It indicates a normal ear where ossicles are intact and no fluid in the middle-ear
How will type AD present
Reduced peak amplitude compared to type A. But, the peak is still present
Explain type AD
There is disruption of the ossicles or flaccid portion of the tympanic membrane
How will type B tympanometry present
Completely flat (there will be no peak)
Explain type B tympanometry
There is reduced compliance of the tympanic membrane due to fluid in the middle ear - meaning all sound will be reflected back
If a type B tympanometry at normal pressure what is the underlying pathology
Otitis Media
If a type B tympanometry at high pressure what is the underlying pathology
Grommets
If a type B tympanometry at low pressure what is the underlying pathology
Ceremen Impaction
What is type C tympanometry
There is a shift in peak of negative middle-ear pressure
What causes type C tympanometry
Resolving otitis media
What are the indications for MRI in hearing loss
- Adult with sensorineural hearing loss and localising signs (facial paraesthesia)
- Adult with asymmetrical sensorineural hearing loss of >15dB difference
What is an MRI trying to exclude in hearing loss
Acoustic neuroma
In terms of anatomy, how can the ear be divided
External ear
Middle ear
Inner ear
What are the two parts of the external ear
- Auricle (Pinna)
2. External auditory meatus
What is the function of the auricle
Directs sound towards the external acoustic meatus
What is the helix
Round cartilaginous structure
What is the concha
Depression in the middle of the auricle
What does the concha lead to
The concha continues as the external acoustic meatus into the skull
What is the external acoustic meatus
Tube that connects the concha to the tympanic membrane
What is the tympanic membrane
Connective tissue that enables middle ear to be to be observed
What is the point where the malleus attaches to the tympanic membrane called
Umbo
Where is the middle ear
Tympanic membrane to inner ear
What is the function of the middle ear
Transmits vibrations from the tympanic membrane to the inner ear via ossicles
What are the two components of the middle ear
Tympanic cavity
Epitympanic recess
What is the tympanic cavity
Contains the ossicles: stapedius, malleus and incus
What is contained lateral to the epitympanic recess
Mastoid air cells
What Is the role of mastoid air cells
When pressure in middle ear is low - they can release air acting as a buffer
What is the acoustic reflex
In response to loud noise the stapedius and tensor tympanic will contract - inhibiting vibrations of auditory canal and transmission of sound
What is the Eustachian tube
Connects the nasopharynx to the middle ear
What is the role of the Eustachian tube
To equalise pressure of middle ear
What is the problem with the Eustachian tube
Acts as source of infection pass to the middle ear
What are the 2 functions of the inner ear
- Convert mechanical signals into electric signals for hearing
- Maintain balance
What are the two components of the inner ear
- Bony Labyrinth
2. Membranous Labyrinth
What is the bony labyrinth
Series of bone cavities in petrous part of temporal bone made of cochlea, vestibule and semi-circular canals filled with perilymph
What is the membranous labyrinth
In body of bony labyrinth = made of cochlear duct, semi-circular ducts, utricle and saccule - filled with endolymph
What are the two openings in the inner ear
Oval window
Round window
What is the oval window
Connects vestibule and middle-ear
What is the round window
Connects middle-ear and scala tympani
What are the 3 parts of the bony labyrinth
Vestibule
Cochlear
Semi-circular canals
What does the vestibule contain
Utricle
Saccule
= both part of membranous labyrinth
What does the cochlea contain
Cochlea duct - used for hearing
What are the 3 semi-circular canals and their role
Posterior
Anterior
Lateral
= role in balance
What type of fluid is the bony labyrinth filled with
perilymph
What type of fluid is the membranous labyrinth filled with
endolymph
what is the membranous labyrinth made of
- Utricle
- Saccule
- Semi-circular ducts
- Cochlea duct
what is the cochlea duct also known as
Organ of corti
what is the role of the saccule
Detects acceleration-deceleration of the head in a vertical plane
what is the role of the utricle
Detects acceleration-deceleration of the head in a horizontal plane
explain semi-circular ducts
on moving the head, the flow of endolymph changes speed or direction. Sensory receptors in the ampulla detect this and send signals to the brain enabling processing of balancing.
How is the cochlea organised
Tonotropic - meaning different frequencies are processed at different parts
Where are high frequencies processed
Base
Where are low frequencies processed
Apex
What is a mnemonic to remember pathway of hearing
E.COLI
Explain pathway of hearing
- Eight nerve
- Cochlear nucleus
- superior Olive
- Lateral lemniscus
- Infeiror colliculus
What causes conductive hearing loss
Defect in outer or middle ear
What are the outer ear causes of conductive hearing loss
- Barotrauma
- Chronic OM resulting in rupture of TM
- External auditory canal atresia
What are the 2 middle ear causes of conductive hearing loss
Cerumen impaction
Otitis media
Otosclerosis
What is otosclerosis
Overgrowth of bone of the stapes causing it to fix to the oval window
Explain the aetiology of otosclerosis
Autosomal dominant condition with incomplete penetrance
What type of patients get otosclerosis
Young female patients:
20-40
How will otosclerosis present clinically
- Progressive bilateral conductive hearing loss
- Tinnitus (75%)
- Mild vertigo (25%)
What is a specific symptom of otosclerosis
Paracusis Willsi = patient’s hear better in noisy environments
What investigations are ordered for otosclerosis
- Otoscopy
- Rinne and Weber’s
- Pure Tone audiometry
- Tympanometry
What will 10% of people have on otoscopy in otosclerosis
Schwartz sign = hyperaemia behind tympanic membrane seen as red discolouration
How will rinne and weber’s test present in otosclerosis
- Rinne negative
- Weber’s = localises to affected ear
What will be seen on pure tone audiometry in otosclerosis
Cahart notch = increase in bone conduction threshold (dip in curve) at 2,000Hz
What is first-line management for otosclerosis
Bone Anchored Hearing Aids
What is surgical management of otosclerosis
Stapedotomy
Stapedectomy
What is stapedotomy
Partial remove stapes
What is stapedectomy
Removal stapes and replacement with prosthesis
Explain surgery in otosclerosis
Surgery is preferred, however it can only be performed in the worst hearing ear - as contralateral previous surgery is a contraindication.
What is sensorineural hearing loss due to
damage to inner ear or vestibular-cochlear nerve
What is the commonest cause of SNHL
presbycusis
What is presbycusis
age-related bilateral high-frequency hearing loss
In which age does presbcycusis occur
incidence increases with age
When is hearing worse in presbycusis
noisy environments
What causes presbycusis
progressive damage to the organ of corti
What will be seen on pure tone audiometry in presbycusis
decrease in air and bone conduction
How is presbycusis managed
hearing aids
What is noise-induced hearing loss
Hearing loss due to exposure to loud noises
What are the two causes of NIHL
- Repeated exposure to sounds >85dB
- One-off exposure to sounds > 120-150dB
How does NIHL present
- Often with loss of high-frequency sounds first
- Difficultly hearing in loud enviroments
Explain pathophysiology of NIHL
- Repeated exposure damages sterocilia on the organ of corti.
- One off exposure to loud noice can cause rupture of TM and conductive hearing loss
What is used as prophylaxis for NIHL
Noise-cancelling headphones
What is used to manage NIHL
Hearing aids
What is menière’s disease
impaired re-absorption of endolymph in the membranous labyrinth leading to accumulation and dilation of the system = endolymphatic hydrops
What age is meniere’s disease most common
40-60y
How does meniere’s disease change with age
Episodes decrease with age
Explain presentation of meniere’s disease
Acute, Attacks usually last 2-4h and present with triad of:
- tinnitus
- unilateral SNHL
- peripheral vertigo
this is associated with
- Horizontal nystagmus
- aural fullness
- positive rhomberg test
How will meniere’s disease present on audiometry
Reduced bone and air conduction in the affected ear. Often, low-frequencies are affected first
What are two other investigations may order for menière’s disease
- Elecetrocohleography
- Posterior fossa MRI
What is electrocochleaography
- Looks at electrical impulses evoked from vestibulocochlear nerve in response to sound
What is used to treat acute attacks of meniere’s disease
Buccal bethistine
What is used as prophylaxis for meniere’s disease
Prochlorperazine
If meniere’s disease persists what is indicated
- Insertion of gentamicin via a grommet
- Labryinthectomy
- Vestibular neurectomy
What are the risks of surgical procedures for menieres disease
Can cause total deafness
what else should be considered in management of meniere’s disease
Driving - individuals should inform DVLA and not drive until symptoms controlled
over what time frame do symptoms resolve in majority of patients
5-10years
what is an acoustic neuroma
benign tumour of schwann cells surrounding vestibular.N
what is the median age of acoustic neuroma onset
50
what % of CPA tumours are acoustic neuromas
90
what does bilateral acoustic neuromas indicate
NF2
what chromosome is mutated in neurofibromatosis 2
chromosome 22
what are the 4 tumours common in NF2
- Meningiomas
- Ependymomas
- Bilateral vestibular
schwannoma - Multiple intracranial
schwannoma
are acoustic neuromas unilateral or bilateral
unilateral (90%). Bilateral acoustic neuromas are only associated with NF2
what nerve is affected early in acoustic neuromas
vestibular-cochlear nerve
what are the 3 early symptoms of acoustic neuroma
- Unilateral tinnitus
- Unilateral SNHL
- Dizziness
why do individuals with acoustic neuroma not get vertigo
Due to the slow-growing nature of the tumour - the body often compromises
what are the late symptoms of acoustic neuromas caused by
Due to damage to trigeminal (CN5) and facial (CN7) nerves
what 2 symptoms are caused by compression of CN5 in acoustic neuroma
- Loss of corneal reflex
- Facial parasthesia
what symptom is caused by compression of CN7 in acoustic neuroma
Facial paralysis
will the forehead be affected in CN7 damage due to acoustic neuroma
The forehead will be affected as it is a LMN paralysis
what is the risk of acoustic neuromas
can compress other posterior fossa structures including the cerebellum and 4th ventricle
what will compression of cerebellum cause
Ataxia
what will compression of the 4th ventricle
Hydrocephalus
who should suspected acoustic neuromas be referred to
urgent referral to ENT
how are acoustic neuromas investigated
- Rinne and Weber’s
- Pure tone audiometry
- MRI of CPA
how will acoustic neuromas present on rinne and weber’s test
SNHL:
- +ve Rinne’s
- Weber’s = intact ear
how will acoustic neuromas present on pure-tone audiometry
Decrease in air and bone conduction
what is main investigation of acoustic neuromas
MRI of CPA
what are indications for MRI in CPA
- Asymmetry in SNHL between ears >15dB
- SNHL and other features
what is primary management for acoustic neuromas
- Active surveillance = MRI 6-12m
what is second-line management for acoustic neuromas
Stereotactic radiosurgery
when is stereotactic radio surgery indicated
- Tumour growth
2. Significant SNHL
What ototoxic effects do antimalarials and aspirin have
Temporary hearing loss
Tinnitus
What ototoxic effects do loop diuretics and macrolides have
Temporary hearing loss
What ototoxic effects do aminoglycosides have
Permanent hearing loss and vestibular effects
What ototoxic effects do antineoplastics have
Permanent hearing loss
what is the definition of sudden hearing loss
loss of more than 30db in 3 contagious frequencies that onsets in less than 3d
how can aetiology of sudden onset hearing loss be divided
unilateral sudden hearing loss and bilateral
what is the 1 cause of bilateral sudden-onset sensorineural HL
autoimmune
what are 7 causes of sudden-onset hearing loss
- Vascular
- NIHL
- Glue ear
- Acoustic neuroma
- Ototoxicity
- Mumps
- Ossicular discontinuity
what is glue ear, what age does it present, how does it present
- Otitis media with effusion
- Peaks at 2-years
- Conductive hearing loss following URTI
how will glue ear present on otoscopy
Effusion in middle ear
what type of hearing loss does glue ear cause
Conductive
what cause ossicular discontinuity
Disruption of ossicles following trauma
what type of hearing loss is present in ossicular discontinuity
Conductive
what type of tympanometry is present in ossicular discontinuity
Ad = flatter peak compared to type A
what type of sudden hearing loss will vascular or autoimmune lead to
SNHL
if no cause is found for sudden hearing loss what is it called
idiopathic sudden sensorineural hearing loss (ISSHL)
Explain referral for sudden onset hearing loss
- Develops sudden hearing loss in <3d in the past 30d = refer to ENT in 24h
- Develops sudden hearing loss in <3d more than 30d ago = refer to ENT in 2W
- Worsening of pre-existing hearing loss = refer to ENT in 2W
What is often given for sudden onset hearing loss
High-dose steroids = Prednisolone (80mg)
If prednisolone is ineffective, what else may be offered
Short hyperbaric oxygen therapy
What are 3 unilateral causes of progressive hearing loss
- Otosclerosis
- Nasopharyngeal carcinoma
- Acoustic neuroma
In which ethnicity are nasopharyngeal carcinomas more common
Chinese/Hong-Kong
How do nasopharyngeal carcinoma present clinically
- Unilateral nasal lump
- Neck lumps
- Epistaxis
- Conductive hearing loss = middle ear effusion on otoscopy
What are two bilateral cases of progressive hearing loss
NIHL
Presbycusis
When are hearing aids offered
If hearing loss is impacting ability to communicate
What is the mechanism of behind the ear hearing aid
Amplifies sound to assist with hearing
What are bone anchored hearing aids
Sound is transmitted directly to the cochlea via bone conduction
What are cochlear implants indicated for
SNHL who has not benefitedd to conventional hearing aids
What are audio induction loops
sound system where hearing loop provides magnetic, wireless signal picked up by hearing aid when set to T. It has a microphone and amplified.