DrVirgo
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Rinne Test compares Air conduction (AC) to Bone Conduction (BC).
Strike a tuning fork and place it on the mastiod process and note the time heard until it cannot be felt. Then place it next to the EAM of same hear and note how long sound is heard for.
(Normally AC>BC -normally twice as long)
-With conductive hearing loss, bone conduction sound is heard longer than or equally as long as air conduction
-With sensorineural hearing loss, air conduction is heard longer than bone conduction in affected ear, but less than 2:1 ratio
-WHY is this?
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| msyamp
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-With conductive hearing loss, bone conduction sound is heard longer than or equally as long as air conduction because nerve is ok and cochlea is ok so bone conduction is ok. so bone conduction is ok but air conduction decreased
-With sensorineural hearing loss, air conduction is heard longer than bone conduction in affected ear, but less than 2:1 ratio . reverse is true here. but here even if air cond is ok. the next step is impaired so less than normal. but it is air conduction iss heard longer because of the normal tympanic apparatus that amplifies sound in aiconduction which is not seen in boneconduction.
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| DrVirgo
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Good explanation msyamp!
If a normal patient has:
Bone conduction time: 30 seconds
Air Conduction time: 15 seconds
Ratio of 2:1 for BC:AC
Can you give an example of BC:AC times and ratio that you would expect in a patient with:
1. Conductive hearing loss
2. Sensorineural hearing loss
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| msyamp
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hey in normal ac>bc . but your values contradict. please rephrase.
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| DrVirgo
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Sorry about that:
If a normal patient has:
AIR conduction time: 30 seconds
BONE Conduction time: 15 seconds
Ratio of 2:1 for AC:BC
Can you give an example of AC:BC times and ratio that you would expect in a patient with:
1. Conductive hearing loss
2. Sensorineural hearing loss
-What I am trying to ask is: In a patient with Conductive hearing loss we know that BC is more than AC. Now is this becuase BC time increases or because AC time decreases?
-And for Sensorineural hearing loss, same question: the ratio is still AC>BC, but less than a 2:1 ratio. Is this because of a change in AC or BC?
thanks.
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| msyamp
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conductive hearing loss
BC 25(inc due to less masking AC 10 du to pathology
sensory neural
BC 5 AC 20 same amount decrease as both are equally affeted
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| DrVirgo
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The orignal values were:
AC: 30
BC: 15
In conductive hearing loss the AC is affected so this number should decrease (as you mentioned 10- I agree). I don't understand what you say about BC: you said inc but gave a value of 25 which is decr. 
In sensorineural hearing loss, the BC is less so BC should decrease (as you mentioned 5- I agree), but why does AC also decrease, and why do they decrease equally? How are they both equally affected here? in Senorineural hearing loss, the tympanic membrane is ok, so why would AC be affected as well?
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| msyamp
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hahaha . in the first one BC is increased from 15 to 25 as i said
second one even if tympanic membrane is ok, the sound will go till tympanum and cochlea but later anyway you get damaged nerve so AC will also be effected
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| DrVirgo
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Sorry, i was looking at wrong values for conduc. BC.
You are right for both!
Great.
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| DrVirgo
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msyamp:
One more thing:
According to: http://www.webster.edu/~davittdc/ear/rinne/rinne....
With sensorineural hearing loss, air conduction is heard longer than bone conduction in affected ear, but less than 2:1 ratio.
In the example you gave me for SN Hearing loss:
you said AC:BC is 20:5 because both decrease equally. This would end up being a ratio of 4:1! This is MORE, not LESS than 2:1 which is supposed to occur in SN hearing loss.
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| DrVirgo
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According to Merck:
[left]Rinne's test compares hearing by air conduction with that by bone conduction. The stem of a vibrating tuning fork is placed in contact with the mastoid process (for bone conduction); then the tines of the still vibrating fork are held near the pinna (for air conduction), and the patient is asked to indicate which stimulus is louder. Normally, the stimulus is heard louder by air conduction (AC) than by bone conduction (BC), so the relationship is AC > BC. With a conductive hearing loss, the relationship is reversed; the bone conduction stimulus is perceived louder than the air conduction stimulus (BC > AC). With a sensorineural hearing loss, both air and bone conduction perceptions are reduced, but the ratio remains the same as that for normal hearing (AC > BC).
Can anyone please confirm this last sentence as I am reading different explanationg from different sources.
Thanks again.[/left]
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