Hearing and deafness Flashcards
Describe the physiology of hearing?
Sound waves travel down our ear canal, the pinnear acts as an amplifier.
The waves cause the ear drum to vibrate which then causes the ossicular chain to vibrate. (malleus, incus and stapes)
The stapes is in contact with the oval window which leads to the vestibule of the inner ear.
By this point the sound waves will have been amplified by up 20 times the original amount.
The conduction continues into the cochlea which is a fluid filled shell shaped tube.
As the cochlea conducts sound waves the fluid moves, this causes the sensory hair cells in the cochlea to move correspondingly, these transduce the mechanical energy into an electrical signal which then travels down the cochlea nn towards the brain.
Hair cells at the base of the cochlea are responsible for picking up higher pitched sounds, whilst hair cells at the apex are responsible for lower pitched sounds.
What is the difference between conductive and sensorineural hearing loss?
Conductive hearing loss is when there is a problem conducting sound waves from anywhere from the outer ear to the ossicles.
Senorineural hearing loss is when there is a problem with the sensory receptors in the cochlea (sensory) or when there is a problem with the neural circuit aka the vestibular nn or auditory centre of the brain (neural)
Patients may also have a mixed pattern of hearing loss where there is conductive and sensorineural loss.
Describe how rinnes and webers test work?
Rinnes: tap the tuning fork and then hold it on the mastoid process and then in front of the ear, it should be louder in front of the ear. If not conductive hearing loss. Positive rinnes is normal. AC>BC
Webers: tap the tuning fork and then place it in the centre of the forehead. It should be heard equally in both ears.
In sensorineural loss it will be louder in the good ear.
In conductive hearing loss it will be louder in the bad ear.
What is pure tone audiometry and tympanometry?
Pure tone audiometry is the key hearing test used to identify hearing threshold levels of an individual, enabling determination of the degree, type and configuration of a hearing loss.
The patient wears headphones and press a button when they can hear a sound.
Tympanometry is a test used to assess middle ear function. The test is performed by inserting the tympanometer probe in the ear canal. The instrument changes the pressure in the ear, generates a pure tone, and measures the eardrum responses to the sound at different pressures.
Which tests can be used in assessing children’s hearing?
‘Toy test’: Tester names a toy and asks the child to point at it. (For children that cannot cooperate with pure tone audiometry)
Visual Reinforcement Audiometry (VRA) for developmental ages of 6 months to 2 years: child turns to the sound stimulus and a puppet lights-up to reward (reinforce) the child’s listening behavior.
To test specifically for sensorineural loss you can use:
Automated otoacoustic emissions (AOAE) test which measures the functioning of the inner ear.
Automated auditory brainstem responses: which measures the electrophysiological response from the brainstem using scalp electrodes.
What is the difference between objective and subjective tinnitus?
Subjective tinnitus is when the patient is complaining of hearing a ringing sound in there ear but it cannot be heard by anyone else. 95%
Objective tinnitus is when the tinnitus can also be heard by someone else if they listen next to the patients ear using a stethoscope. 5%
What is physiological and pathological tinnitus?
physiological tinnitus = Short bursts of tinnitus lasting
pathological tinnitus = more than 15 minutes
