Deafness Flashcards
How can deafness be classified?
Conductive
or
Senorineural
What is conductive hearing loss?
Pathology affecting the external or the middle ear
What is sensorineural hearing loss?
Pathology affecting the inner ear (cochlear, auditory nerve or auditory centres in the brain)
Causes of conductive hearing loss?
External ear occlusion - wax
Glue ear
Infection - otitis media, otitis externa
Ear trauma - perforated TM
Otosclerosis
Iatrogenic
Cholesteatoma
Exostoses - benign bone growth
Foreign body
Causes of sensorineural hearing loss?
Idiopathic
Congenital
Presbyacusis
Viral infection
Meniere’s disease
Acoustic neuroma
Trauma / noise exposure
Drugs - loop diuretics, gentamicin, cisplatin (chemo)
Labyrinthitis
Neurological condition - MS, stroke, brain tumour
What investigations can be done for hearing loss?
Audiometry - Rinne’s test and Weber’s test
Pure tone audiogram
Tympanometry
Describe how a Rinne’s test is done?
Tuning fork placed over mastoid process.
Then placed infant of ear - over EAM.
Describe how a Weber’s test is done?
Tuning fork placed in the middle of the forehead equidistant from the pt’s ears
Pt asked which side is loudest
Result of Weber’s test in pt with no hearing loss?
Sound heard equally by both ears
Result of Weber’s test in pt with conductive hearing loss?
Lateralises to the affected ear.
Why? As pathology is in external or middle ear - the external ambient noise is lost due to being blocked. so the tuning fork sound (which travels by bone conduction) is heard louder in the affected ear.
In their ear which has no conductive hearing loss - sound waves from ambient noise can be heard, so tuning fork sounds quieter than ear with blockage.
Result of Weber’s test in pt with sensorineural hearing loss?
Lateralises to the unaffected ear.
(i.e. away from affected ear).
Why? problem is in inner ear. So vibration will NOT be conducted from the bone to the cochlear in affected ear = does not hear it on this side.
Result of Rinne’s test in pt with no hearing loss?
Air conduction > bone conduction bilaterally
Result of Rinne’s test in pt with conductive hearing loss?
Bone conduction > air conduction in affected ear.
Air conduction > bone conduction in unaffected ear (i.e. unaffected ear is normal).
Result of Rinne’s test in pt with sensorineural hearing loss?
Air conduction > bone conduction bilaterally.
What is normal hearing frequency in dB?
20 dB
What type of hearing loss is presbycusis?
Sensorineural
Pathophysiology of presbycusis?
Atrophy of sensory hair cells and neurons in cochlea
Presentation/Hx of pt with presbycusis?
Gradual/ slowly progressing
Speech becomes difficult to understand
Needing to increase TV volume
Hard to use telephone
Lose direction of sound
Worsening Sx in noisy environment
Investigations of pt with presbycusis?
Otoscopy - will be normal. Used to rule out otosclerosis, cholesteatoma, conductive hearing loss.
Tympanometry - normal middle ear function
Audiometry - bilateral sensorineural hearing loss
Inheritance pattern of otosclerosis?
Autosomal dominant.
Pathophysiology of otosclerosis?
Bone around base of stapes thickens, fuses with bone of cochlea.
This prevents normal function onto cochlea, gets progressively worse.
Management for otosclerosis?
Initially - hearing aids to allow for hearing amplification.
Surgical replacement of stapes = stapedectomy
Presentation of meniere’s?
Unilateral
30-60yrs old
Sudden attacks of paroxysmal vertigo
Deafness
Tinnitus
Attacks come in clusters, have periods of remission
N+V
How is Meniere’s managed?
Bed rest and antihistamines
Presentation of otosclerosis?
20-40yrs
Condutive deafness
Tinnitus
FHx is strong
What drugs can be ototoxic?
Aminoglycosides - gentamicin
Furosemide
Aspirin
