Deafness Flashcards
What are the types of deafness? Define them.
Conductive: a problem conducting sound waves along the route through the outer ear, TM and middle ear
Sensorineural: the problem is in the inner ear, vestibulocochlear nerve or brain
Mixed
What’s the normal threshold of hearing?
Can hear sounds as quiet as 0 - 20dB
How is hearing loss categorised?
Quietest sound they can hear is:
Mild: 25-40dB
Moderate 40-70dB
Severe: 70-95dB
Profound: >95dB
What are some causes of conductive hearing loss?
Occlusion: cerumen, foreign body, oedema
Glue ear
Infection: otitis externa, media
TM perforation
Growths: tumours, cysts, cholesteatoma
Otosclerosis
Myringosclerosis
TMJ syndrome
What causes TM perforation?
Otitis media
Chronic otitis
Trauma: water, barotrauma
Surgery
What is otosclerosis and how does it cause deafness?
What type of deafness does it cause?
Conductive
Abnormal bone deposition at base of stapes preventing normal ossicular vibration
What is myringosclerosis and how does it cause deafness?
What type of deafness does it cause?
Conductive
Deposition of irregular white calcium patches on the TM
If it extends enough it can cause deafness
What is TMJ syndrome and how does it cause deafness?
What type of deafness does it cause?
Conductive
Locking of jaw, pain in jaw and face
Hearing loss caused by spasms of muscles of inner ear
Self-limiting
What are the clinical features of otosclerosis?
Pathophysiology?
Progressive bilateral conductive hearing loss
Tinnitus
Autosomal dominant
Abnormal bone deposition at the base of the stapes which affects conduction of sounds waves through the ossicles
Management of otosclerosis?
Hearing aids
Stapedectomy or otomy
What are the causes of sensorineural hearing loss?
Congenital:
Abnormal or absent cochlear hair cells, infections, hypoplastic nerves
Syndromes
Acquired:
Damage to V-C nerve (VIII)
Meniere’s disease
Presbycusis
Which congenital infections cause deafness?
TORCH
Toxoplasmosis
Rubella
CMV
HIV, Herpes
What congenital problems can cause deafness?
Abnormal or absent cochlear hair cells
Infections: rubella, toxoplasmosis
Hypoplastic nerves
Abnormal cochlea
What is presbycusis?
Pathophysiology
Normal age-related progressive bilateral sensorineural hearing loss
Especially at high frequencies
Caused by cochlear and ganglion degeneration and vascular atrophy
What are the clinical features of presbycusis?
Older age onset
Insidious high frequency hearing loss
Especially voiceless consonants
Management of presbycusis?
Hearing aids
Assistive listening devices
Cochlear implants
How does noise-induced hearing loss happen?
Overloading and damaging the sensorineural apparatus in the inner ear
Exposure to excessive noise causes a temporary shift in the stimulus threshold of the hair cells of inner ear
If this happens a lot then it becomes a permanent shift
What is an acoustic neuroma?
Pathophysiology?
Tumour of the Schwann cells which myelinate the VIII nerve
Most are from the vestibular division rather than cochlear
Typically benign but can cause problems due to mass effect and pressure on local structures
Presentation of acoustic neuroma?
Unilateral or asymmetrical hearing loss
Tinnitus
Insidious or acute onset
Impaired facial sensation or pain
Balance problems (often quite subtle)
Earache
Ataxia due to cerebellar compression
Raised ICP: headache, visual loss, decreased consciousness
Investigations of acoustic neuroma?
Audiology
MRI
Management of acoustic neuroma?
Depends on growth
Three options:
- microsurgery
- stereotactic radiosurgery
- observation
Define and describe tinnitus?
Hearing of sound when no external sound is present
Ringing, clicking, hissing, roaring
Interferes with concentration
What causes tinnitus?
Noise induced hearing loss
Infections
Vasculitis
Meniere’s
Brain tumours
Emotional stress
Head injury
Earwax
What two types of tinnitus are there? Give causes.
Subjective: no acoustic stimulus
- otological
- neurological
- infections: meningitis
- drugs
- TMJ syndrome
Objective: a noise is being generated in the head which is being heard
- pulsatile: blood movements
- muscular spasms
- spontaneous otoacoustic emissions
What devices are available to help with hearing?
Hearing aid
Bone-anchored hearing aid
Cochlear implant
How does a hearing aid work?
It amplifies sound
How does a bone-anchored hearing aid work?
It uses bone conduction as a way to conduct sound if the usual route of conduction is broken
Bypasses external auditory canal and middle ear. Sound goes from bone to cochlea
How does a cochlear implant work?
It stimulates the cells of the auditory spiral ganglion to produce a sense of sound
It directly stimulates the auditory nerve using electrical signals
What ways are newborns’ hearing screened
Otoacoustic emissions (detects tiny cochlear sounds produced by movements of hair cells)
Audiological brainstem responses: measure brainwave activity in response to sounds
How can childrens’ hearing be tested?
Distraction testing: makes noises behind and beside child and see if they turn their head
Visually reinforced audiometry: child turns head to sound stimulus and is rewarded by toy
Speech discrimination: child touches objects they are told to
