Post by Brian G on Nov 13, 2014 2:06:01 GMT
If I understood it in A&P, I forgot, and today's explanation in the lecture didn't help. It wasn't until I read the first couple of paragraphs in Wikipedia until I finally understood what the Weber and Rinne test are all about.
Weber test
A patient with a unilateral conductive hearing loss would hear the tuning fork loudest in the affected ear. This finding is because the conduction problem of the middle ear (incus, malleus, stapes, and eustachian tube) masks the ambient noise of the room, while the well-functioning inner ear (cochlea with its basilar membrane) picks the sound up via the bones of the skull, causing it to be perceived as a louder sound in the affected ear. Another theory, however, is based on the occlusion effect described by Tonndorf et al. in 1966. Lower frequency sounds (as made by the 256 Hz fork) that are transferred through the bone to the ear canal escape from the canal. If an occlusion is present, the sound cannot escape and appears louder on the ear with the conductive hearing loss.
Conductive hearing loss can be mimicked by plugging one ear with a finger and performing the Rinne and Weber tests, which will help clarify the above. Humming a constant note and then plugging one ear is a good way to mimic the findings of the Weber test in conductive hearing loss. The simulation of the Weber test is the basis for the Bing test.
Rinne test
Procedure
The Rinne test is performed by placing a low frequency (512 Hz) vibrating tuning fork against the patient's mastoid bone and asking the patient to tell you when the sound is no longer heard. Once they signal they can't hear it, quickly position the still vibrating tuning fork 1–2 cm from the auditory canal, and again ask the patient to tell you if they are able to hear the tuning fork.
Results
Normal Hearing: Air conduction should be greater than bone conduction and so the patient should be able to hear the tuning fork next to the pinna after they can no longer hear it when held against the mastoid.
Abnormal Hearing:
If they are not able to hear the tuning fork after mastoid test, it means that their bone conduction is greater than their air conduction. This indicates there is something inhibiting the passage of sound waves from the ear canal, through the middle ear apparatus and into the cochlea (i.e., there is a conductive hearing loss).
In sensorineural hearing loss the ability to sense the tuning fork by both bone and air conduction is equally diminished, implying they will hear the tuning fork by air conduction after they can no longer hear it through bone conduction. This pattern is similar to what is found in people with normal hearing, but patients with sensorineural hearing loss will indicate that the sound has stopped much earlier. This can be revealed by the investigator by placing the fork close to her own ear after the patient indicates that the sound has subsided, noting that the sound from the fork is still loud and clear to a normal ear.
Sensorineural hearing loss (SNHL) is a type of hearing loss in which the root cause lies in the vestibulocochlear nerve (cranial nerve VIII), the inner ear, or central processing centers of the brain. Sensorineural hearing loss can be mild, moderate, or severe, including total deafness.
Weber test
A patient with a unilateral conductive hearing loss would hear the tuning fork loudest in the affected ear. This finding is because the conduction problem of the middle ear (incus, malleus, stapes, and eustachian tube) masks the ambient noise of the room, while the well-functioning inner ear (cochlea with its basilar membrane) picks the sound up via the bones of the skull, causing it to be perceived as a louder sound in the affected ear. Another theory, however, is based on the occlusion effect described by Tonndorf et al. in 1966. Lower frequency sounds (as made by the 256 Hz fork) that are transferred through the bone to the ear canal escape from the canal. If an occlusion is present, the sound cannot escape and appears louder on the ear with the conductive hearing loss.
Conductive hearing loss can be mimicked by plugging one ear with a finger and performing the Rinne and Weber tests, which will help clarify the above. Humming a constant note and then plugging one ear is a good way to mimic the findings of the Weber test in conductive hearing loss. The simulation of the Weber test is the basis for the Bing test.
Rinne test
Procedure
The Rinne test is performed by placing a low frequency (512 Hz) vibrating tuning fork against the patient's mastoid bone and asking the patient to tell you when the sound is no longer heard. Once they signal they can't hear it, quickly position the still vibrating tuning fork 1–2 cm from the auditory canal, and again ask the patient to tell you if they are able to hear the tuning fork.
Results
Normal Hearing: Air conduction should be greater than bone conduction and so the patient should be able to hear the tuning fork next to the pinna after they can no longer hear it when held against the mastoid.
Abnormal Hearing:
If they are not able to hear the tuning fork after mastoid test, it means that their bone conduction is greater than their air conduction. This indicates there is something inhibiting the passage of sound waves from the ear canal, through the middle ear apparatus and into the cochlea (i.e., there is a conductive hearing loss).
In sensorineural hearing loss the ability to sense the tuning fork by both bone and air conduction is equally diminished, implying they will hear the tuning fork by air conduction after they can no longer hear it through bone conduction. This pattern is similar to what is found in people with normal hearing, but patients with sensorineural hearing loss will indicate that the sound has stopped much earlier. This can be revealed by the investigator by placing the fork close to her own ear after the patient indicates that the sound has subsided, noting that the sound from the fork is still loud and clear to a normal ear.
Sensorineural hearing loss (SNHL) is a type of hearing loss in which the root cause lies in the vestibulocochlear nerve (cranial nerve VIII), the inner ear, or central processing centers of the brain. Sensorineural hearing loss can be mild, moderate, or severe, including total deafness.