ENT (A) pre-work Flashcards
Two main physiological functions of ear
- Hearing
- Balance
What happens in terms of sound waves, vibrations and electrical energy for us to hear?
- Pinna, EAM and tympanic membrane collect sound waves and transmit them
- Ossicles - malleus, incus and stapes vibrate against eachother amplifying the sound waves
- Stapes vibrates at oval window
- This causes fluid called endolymph to move in cochlea
- Fluid movement moves sterocilia in cochlea organ of conti
- = transmits APs so electrical energy via VC nerve to brain to hear - primary auditory cortex in temporal lobe
Symptoms of problems with ear
- Otorrhoea - discharge
- Otalgia
- Hearing loss - sensorineural or conductive
- Tinnitus
- Vertigo
- Facial nerve palsy - goes through petrous bone
Clinical exam techniques for ear
- Inspect - external ear, EAM and tympanic membrane using otoscope. Also inspect mastoid - is ear pushed forwards?
- Palpate around ear and mastoid process - tenderness?, inc pre and post auricular lymph nodes, palpate tragus - otitis externa?
- Weber - vibrating tuning fork in centre of head - is it symmetrical? louder on one side?
- Rinne - place on mastoid process tell me when you can’t hear, then place it in front of ear - can you hear it now?
Conductive vs sensorineural hearing loss
- Conductive - problem with external or middle ear
- Sensorineural - problem with inner ear - cochlea
Weber and Rinne test results
Weber test:
* Normally sound should be midline
* In conductive loss, sound lateralises towards affected ear (eg if loss in R, sound would be more R sided) as there is loss of ambient noise
* In sensorineural, sound lateralises away from affected ear (so if R affected, sound sounds louder in L ear)
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Rinne
* AC normally better than BC
* In conductive BC is better than AC
* In sensorineural conduction is normal so AC is better than BC
What is a pure tone threshold?
- Pure tones are sounds of single frequencies
- Pure tone threshold is the softest level (lowest volume) at which a person can hear a pure tone
- Threshold is usually measured in decibles
- Noises are played at different frequencies and decibles to establish which ones you can and cannot hear
- The lower the threshold in decibles the more sensitive your ears are to that frequency (so better at hearing it as it is lower volume but you can still hear it)
How is air conduction measured?
- Presenting a pure tone to the ear through an earphone and measuring the lowest intensity in decibels (dB) at which this tone is perceived 50% of the time.
- It is measured at 250, 500, 1000, 2000, 4000 and 8000
How is bone conduction measured?
- Bone vibrator on the mastoid process
- Tested at 500-4000Hz
What is masking?
- Presenting a sound to the non-test ear
- Preventing it from detecting the sound given to the test ear
- Prevents cross hearing which occurs from bone conduction to contralateral cochlea
How would high frequency hearing loss affect someone?
- May be unable to hear birds
- Some alarms
- Trees rustling
- Sounds like ‘th’ ‘f’ ‘s’ ‘ee’
How would low frequency hearing loss affect someone?
- May not be able to hear running water/tap dripping
- Dog barks
- Certain sounds eg ‘v’, ‘z’, ‘j’
How can deafness in childhood affect someone?
- Affect speech and language development
- Following directions in loud/noisy places - difficult
- Making friends and interacting with others - more difficult
- Learning to read
- Need specialist education or changes - eg sit at front of class, teacher not turn their back while talking etc
Impacts of hearing loss with older age + dementia
- Increase risk of confusion
- Increases dementia risk itself
- Misdiagnosis of dementia
- Harder to communicate with loved ones
Impacts of hearing loss and visual impairement
- Higher risk of dementia?
- Social isolation - difficulty comunicating
- Lack of public acceptance
