I don't really understand Weber's test

[Nuieve]

I don't understand the logic behind this explanation:

"A patient with unilateral conductive loss perceives the sound in the ear with the conductive loss i.e. if the right has a conductive loss, the sound lateralises to the right ear."

I thought if any ear has ANY kind of hearing loss, than the sound will always be better sensed in the opposite (healthier) ear.

[morte, LPN, LVN]

weber's test the stem of a vibrating tuning fork is placed on the vertex or midline of the forehead. if the sound is heard best in the affected ear, it suggests conductive hearing loss; if heard best in the normal ear, it suggests sensorineural hearing loss

editorweatherall's mysterya positive weber's test in the normal ear in unilateral sensorineural hearing loss but in the affected ear in unilateral conductive hearing losshas baffled many neurologists and ear, nose, and throat surgeons for some time; i wonder whether my explanation would convince him.1

the word conduction is used confusingly by ear, nose, and throat surgeons and neurologists to describe normal transmission of sound from the outside world to the ear. everything apart from the sensorineural aspect of the hearing is thought to be conductive. the sound is normally conducted (transmitted) through the air through the external ear into the middle ear. this makes air a better sound conductor (when defined this way) than a solid object.

it is, however, clear to any engineering student that bone or any denser object is a better conductor of sound than is air. when the tuning fork is placed directly on the bone, there is no significant sound transmission from the tuning fork directly through the air. the conduction being tested is that through bone to the inner ear.

the air medium in the ear, being a less efficient transmitter of sound, results in sound energy loss at the interface of bone and air. the resultant sound energy to the inner ear is therefore less. if you have a more solid (denser) object in the ear (which would have resulted in conduction deafness (as defined by doctors) the sound conduction is actually better. less energy is lost, and the sound is localised to that side in weber's test.

if both ears are blocked but with different materials with different conductive properties, positive results in weber's test would localise to the side with the denser and therefore better sound conducting material. you could test this by blocking your ear with one finger and the other with another material, comparing the sounds and comparing each with air. nice little study for a neurologist, i say.

chima e mbubaegbu, consultant orthopaedic surgeon.

homerton university hospital nhs trust, london e9 6sr [email protected]

1. weatherall mw. the mysterious weber's test. bmj 2002; 325: 26[free full text]. (6 july.)

[Nuieve]

Oh, that actually makes sense. Thanks! :)

[morte, LPN, LVN]

lucky find,lol.....

[Daytonite, BSN, RN]

this is the logic and explanation behind the weber test according to mark h. swartz in his textbook of physical diagnosis: history and examination, third edition, page 204 on the physical examination of the ear: "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 effected ear hears and feels the vibrating tuning fork better than does the normal ear. in patients with unilateral sensorineural deafness, the sound is not heard on the affected side but is heard by, or localized to, the unaffected ear."

[Nuieve]

Ok, now it's crystal clear. Thanks! :)

[GingerSue]

and in my assessment textbook

Weber Test:

normally sound is equally loud in both ears; sound does not lateralize

when there is conductive loss - sound lateralizes to the poorer ear due to

background room noise which masks hearing in the normal ear. The poorer ear (the one with conductive loss) is not distracted by background noise, thus has a better chance to hear bone-conducted sound.

when there is sensorineural loss - sound lateralizes to better ear or unaffected ear. The poor ear (the one with nerve loss) is unable to perceive the sound.