Rinne's test

Music in My Heart · Sep 15, 2007

i have a few questions about the rinne's test. i understand how it is done, and i understand what the results mean, but i don't understand why.
1. when the tuning fork is placed against the mastoid process, this is called bone conduction, correct? well, what i'm wondering is - does the term "bone conduction" refer to the bones of the middle ear (ie, the auditory ossicles)? if not, then what does "bone conduction" actually refer to?
bone conduction refers to the conduction of the vibration through the temporal bone.
strictly speaking, the vibration is never conducted through the ossicles. rather, the vibrations of the tympanic membrane cause displacement of the ossicles which then cause displacement of the oval window which results in a standing wave in the cochlear duct.
the ossicles transmit the vibration, they don't conduct it.
2. when the tuning fork is placed against the mastoid, does that stimulate the auditory ossicles, normally? yes, the vibrations of the fork are conducted through the temporal bone and cause a vibration in the tympanic membrane. however, the vibrations are also conducted through the temporal bone directly to the cochlea and contribute to the standing wave that way.
if conduction loss is present, will the auditory ossicles still be stimulated and made to function? in conduction deafness, the ossicles may not be displaced as normal.
if not, then how do the vibrations actually reach the vestibulocochlear nerve? as mentioned above, they are conducted through the temporal bone directly to the cochlea.
in other words, is the vestibulocochlear nerve connected to the mastoid process? (if not, then how is that nerve being stimulated?) no.
3. why is it exactly that sound is heard longer through air if sensorineural impairment exists? actually, how can hearing occur at all if sensorineural impairment exists? the way i see it, you can tap on that nerve till you're blue in the face, but if it's not working, then no sound information will ever be sent to the brain, correct? my understanding is that it's not a matter of "longer" but rather a matter of "louder." rinne's test detects conduction deafness. if there is conduction deafness, the sound heard through the temporal bone will not be heard through the auditory meatus.
sensory deafness is detected by weber's test, not rinne's test.
i don't really understand your question. however, be aware that "impairment" doesn't imply a complete lack of function but rather diminished function (which may or may not be a total lack of function).
in thinking about it over dinner, it occurs to me that "longer" equates with "louder" since the latter refers to a larger amplitude of compaction/rarefaction which thus takes "longer" to decrease to a point where it's no longer perceived.
4. finally - if sound is heard longer through air in both normal hearing and in sensorineural loss, then how do you tell the distinguish between those two conditions? is it simply a matter of hearing acuity being reduced in sensorineural loss? if so, how can you actually tell that it's reduced? in other words, nothing that i've read says anything about how long or how loud air conduction is supposed to be heard - merely that it will be heard longer than bone conduction in both normal loss and sensorineural loss. which leaves me wondering how to tell the difference...? time for me to have dinner. i'll edit this later. again, though, sensory deafness is detected through weber's test, not rinne's test.
i know these are probably ridiculously stupid questions, and maybe i'm just thinking about it all too hard, but i just want to understand the process and not merely memorize rote facts like a zombie. you are to be commended.
much thanks,
the jedi.

.....

Daytonite, BSN, RN · Sep 15, 2007

you always ask such probing questions!

i don't know that i can find the answer to all your questions. you should check some of the physical exam resources from the medical colleges on the health assessment resources, techniques, and forms sticky thread (https://allnurses.com/forums/f205/health-assessment-resources-techniques-forms-145091.html) as well as a good anatomy book because i think that is where you're going to find most of your answers.

this is what textbook of physical diagnosis: history and examination by mark h. swartz has to say about these tests (page 204)

"

the rinne test

the rinne test

compares

air conduction with bone conduction. each ear is tested separately. the examiner should strike a 512 hz tuning fork and place its handle on the mastoid tip near the external auditory meatus. the patient is then asked whether he or she hears the sound and to indicate when it is no longer heard. when the patient can no longer hear the sound, the times of the vibrating tuning fork are placed in front of the external auditory meatus of the same ear, and the patient is asked whether he or she can still hear the sound. the tines of the vibrating tuning fork should not touch any hair, because the patient may have a hearing impairment but may still feel the vibration.

normally, air conduction (ac) is better than bone conduction (bc), and patients are able to hear the tuning fork at the external auditory meatus after they can no longer hear it on the mastoid tip; this is a

rinne positive

test (ac > bc). patients with a conductive hearing loss, however, have bone conduction that is better than air conduction; a

rinne negative

test (bc > ac). patients with sensorineural deafness have impaired air and bone conduction but maintain the normal ac > bc response. the middle ear amplifies the sound in both positions.

if there is total deafness in one ear, the patient may hear the tuning fork even when it is placed on the mastoid process of the deaf ear. this is due to the transmission of vibrations by bone across the skull to the opposite side where they are sensed by the healthy ear. this is termed a

false-negative rinne

.

the weber test

the weber test compares bone conduction in both ears and determines whether monaural impairment is neural or conductive in origin. stand in front of the patient and place a vibrating 512 hz tuning fork firmly against the center of the patient's forehead. ask the patient to indicate whether he or she hears or feels the sound iin the right ear, in the left ear, or in the middle of the forehead. hearing the sound, or feeling the vibration, in the middle is the normal response. if the sound is not heard in the middle, the sound is said to be

lateralized

, and a hearing loss is present. sound is lateralized to the

affected

side in conductive deafness. try it on yourself. occlude your right ear and place a vibrating tuning fork iin the center of your forehead. where do you hear it? on the

right

. you have created a conductive hearing loss on the right by blocking the right canal; the sound is lateralized to the right side.

the explanation for the weber test is based on the masking effect of background noise. in normal conditions, there is considerable background noise, which reaches the tympanic membrane by air conduction. this tends to mask the sound of the tuning fork heard by bone conduction. in an ear with a conductive hearing loss, the air conduction is decreased, and the masking effect is therefore diminished. thus, the affected ear hears and feels the vibrating tuning fork better than does the normal ear.

in patient with unilateral sensorineural deafness, the sound is not heard on the affected side but is heard by, or localized to, the

unaffected

ear."

my old notes from my assessment class indicate that rinne and weber are tests of the 8th cranial nerve (vestibulocochlear, sometimes called the acoustic) which is responsible for hearing and balance. my knowledge of anatomy goes this far: vibration sets off the wave motions of the hairs in the organ of corti which are then translated to impulses and conducted along through the acoustic nerve. that is how we hear sound.

these hairs are stimulated to movement (which then sends off a stimulus through the acoustic nerve resulting in the brain "hearing" sound) in two ways:

by a physical stimulus of the bones of the skull (the tuning fork held against the mastoid)
by sound (music, talking, etc.)

hearing is impeded by

sound not being able to get to the nerve to create a stimulus
acoustic nerve failure

the rinne test, as dr. swartz says, only compares the air and bone conduction. i think that for more specific hearing tests, other testing needs to be done. these are just tests of gross hearing ability. in order for sound to be appreciated, the hairs in the organ of corti must be set into motion. from what i can gather, and i don't have an anatomy book to confirm this, these are the only two ways that it can happen and the rinne and weber tests just distinguish between them is all. from what i can deduce, bone conduction of sound is a very passive thing. it just happens once the tuning fork is applied to the mastoid bone. there doesn't seem to be a way to actively block the vibration of any of these bones since they are all interconnected. if there was, it would be some sort of pathological condition, i'm sure (see next paragraph).

sensorineural deafness is due to "defective function of the cochlea or acoustic nerve" (page 490, taber's cyclopedic medical dictionary, 18th edition, published in 1997 by f.a. davis company). conduction deafness "results from any condition that prevents sound waves from being transmitted to the auditory receptors. it may result from wax obstructing the external auditory meatus, inflammation of the middle ear, ankylosis of the ear bones, or fixation of the footplate of the stirrup. [note: these are things that would impede vibration]" (page 490, taber's cyclopedic medical dictionary, 18th edition, published in 1997 by f.a. davis company).

Jedi of Zen · Sep 16, 2007

"Longer" (not "louder") is the term that Potter & Perry uses in Fundamentals of Nursing, 6th edition,. So that's what I'm referring to. (Not that this book is ever vague about anything, btw... )

I'm still trying to sort through it all, but your explanation is helping for the time being. Thank you very much for your time, and even for thinking about it over dinner!

Jedi of Zen · Sep 16, 2007

Thanks Daytonite. I have a test coming up, and I have lots more questions, but I'll try to spare you any further questions for right now. :)