This week we will complete the ear evaluation and specifically look at AUDIOGRAMS. They are a very useful tool to determine if a patient has conductive or sensorineural hearing deficit, and to what extent.
The frequency (pitch) is plotted on the x-axis, and the intensity on the y-axis.
Normal hearing is defined as 15dB or better.
The test involves assessing air conduction (o) and bone conduction
Air conduction assesses hearing sensitivity when the signal is transmitted through the outer, middle, and inner ear and then through the brain.
Bone conduction assesses hearing sensitivity when the signal is transmitted through the bones of the skull to the cochlea and through the auditory pathways of the brain.
1) Conductive hearing loss- Nml bone conduction, air conduction poorer than normal by at least 10dB, i.e. otitis media with/without effusion, ear wax
2) Sensorineural hearing loss- both air and bone conduction poorer than normal, and within 10dB of each other; secondary to cochlear abnormality and/or abnormality of auditory nerve or central auditory pathways i.e. cochlear damage (i.e. noise induced), CN8 damage
3) Mixed hearing loss- loss of both conductive and sensorineural components- Pure tone air conduction thresholds are poorer than bone conduction thresholds by more than 10dB and bone conduction thresholds are less than 25 dB
Get used to and comfortable looking at these- they are loved by the boards.
How is it done?