Hearing loss Flashcards
Hearing loss may be unilateral or bilateral.
What are the most common causes of hearing loss?
Excessive ear wax
Otitis media
Otitis externa
What are some other causes of hearing loss?
Presbycusis
Otosclerosis
Glue ear (otitis media with effusion)
Meniere’s disease
Drug ototoxicity
Noise damage
Acoustic neuroma (aka vestibular schwannomas)
What are the causes of conductive hearing loss?
- Excessive earwax occluding the canal
=> blocked feeling
=> wax on otoscopy - Otitis media with effusion (glue ear)
=> popping/clicking pressure
=> dull tympanic membrane/fluid level on otoscopy
=> tympanogram = flat trace - Tympanic membrane perforation
=> middle ear discharge if active infection
=> tympanic perforation - Otosclerosis
=> unilateral or bilateral
=> red tinge to TM on otoscopy due to vessel injection on promontory (cochlear otosclerosis)
=> CT, pure tone audiometry - Cholesteatoma
=> chronic smelly discharging ear
=> deep retraction pocket with keratin collection
=> CT to assess extent of disease
What are the causes of sensorineural hearing loss?
- Presbycusis
=> bilateral gradual onset
=> normal otoscopy
=> pure tone audiometry - Noise induced hearing loss (NIHL)
=> tinnitus
=> normal otoscopy
=> pure tone audiometry - raised threshold at 4kHz - Vestibular schwannoma (acoustic neuroma)
=> asymmetrical hearing loss
=> normal otoscopy
=> MRI - Complications of meningitis
=> important to exclude in children who have had meningitis
=> normal otoscopy
=> MRI might identify labyrinthine obliteration - Acute sensorineural loss
=> tinnitus + vertigo
=> normal otoscopy
=> MRI, autoimmune scnreen
How do you investigate hearing loss?
Pure tone audiometry
Rinnes & Webers
What is pure tone audiometry?
Records the quietest sound that can be heard with each ear at various frequencies i.e. the hearing threshold.
A whisper from 1m has an intensity of 30dB,
Normal conversational voice is 60dB,
Shouting equates to about 90dB
Discomfort at around 120dB.
Explain Weber’s & Rinne’s test.
Weber & Rinne differentiate between sensorineural and conductive hearing loss
Rinne’s test:
=> Vibrate base of tuning fork on mastoid process to test bone conduction
=> Then adjust tuning fork so its prongs are adjacent to external auditory meatus to test air conduction
=> Ask patient which is louder - behind ear or in front?
=> Air conduction > bone conduction in normal hearing (Positive Rinne’s)
=> Bone > Air conduction (Negative Rinne) = external or middle ear disease affecting ear conduction, therefore conductive hearing loss
Weber’s test: Helps lateralise which ear the defect is in
=> Vibrate 512Hz tuning fork to the midline of the forehead, apex of head
=> “Louder” ear can be due to a conductive hearing loss in that (loud) ear or a sensorineural hearing loss in the other ear
- Rinne’s test: Bone > air conduction in right ear
Weber’s test: Louder in right ear
=> conductive hearing loss in right ear
- Rinne’s test: Air > bone conduction
Weber’s test: central, equal hearing in both
=> Normal or bilateral sensorineural hearing loss i.e. presbyacusis
- Rinne’s test:
Air > bone conduction in left ear
Bone > Air conduction in right ear
Weber’s test: Louder in left ear
=> right sensorineural hearing loss in opposite ear
How do you manage hearing loss?
Hearing aids for mild to profound hearing loss trialled up to 3-4 months
Surgery:
- Tympanoplasty: repair tympanic membrane if recurrent ear infections
- Stapedectomy: prosthesis to bypass fixed stapes in otosclerosis to allow sound transmission
- Bone anchored hearing aid for conductive, mixed conductive/sensori-neural hearing aid
- Cochlear implant for profound sensorineural hearing loss and after 3-4 months trial of hearing aids
- Midline ear implant for conductive/mixed hearing loss
What is presbycusis?
Presbycusis = type of sensorineural hearing loss
=> affects elderly individuals
=> high frequency hearing affected bilaterally - can lead to conversation difficulties especially in noisy environments
=> gradual progression as sensory hair cells and neurones atrophy in the cochlea over time
What causes presbycusis?
Cause unknown but likely to be multifactorial:
- Arteriosclerosis - diminished perfusion and oxygenation of the cochlea => damage to inner ear structures
- Diabetes - acceleration of arteriosclerosis
- Accumulated exposure to noise
- Drug exposure i.e. salicylates, chemotherapy agents etc
- Stress
- Genetics
What are the signs and symptoms of presbycusis?
Patients present with chronic, slow progressing history of:
=> speech becoming difficult to understand
=> need for increased volume on the television or radio
=> difficulty using telephone
=> loss of directionality of sound
=> worsening of symptoms in noise environments
=> hyperacusis - heightened sensitivity to certain frequencies of sound
=> tinnitus
Possible weber’s test bone conduction localisation to one side if sensorineural hearing loss not completely bilateral
How do you investigate presbycusis?
- Otoscopy
=> Normal
=> helps rule out osteosclerosis, cholesteatoma and conductive hearing loss i.e. foreign body / impacted wax - Tympanometry
=> Normal middle ear function with hearing loss - Audiometry
=> Bilateral sensorineural pattern hearing loss - Blood tests
=> inflammatory markers / specific antibodies = normal
What is otosclerosis?
Replacement of normal bone by vascular spongy bone.
=> progressive conductive deafness due to fixation of stapes to the oval window
=> autosomal dominant - positive family history
=> typically affects young adults
=> onset 20-40 years
=> tinnitus
=> normal tympanic membrane (10% with flamingo tinge caused by hyperaemia)
Managed by hearing aid / stapedectomy
What is sudden onset sensorineural hearing loss?
How is it treated?
Sudden-onset sensorineural hearing loss (SSNHL) requires urgent referral to ENT.
The majority of SSNHL cases are idiopathic
An MRI scan is usually performed to exclude a vestibular schwannoma.
High-dose oral corticosteroids are used by ENT for all cases of SSNHL
