Y DOES CAHART NOTCH OCCUR????

u ppl ll be familiar with the term cahart notch !! ie., the dip in bone conduction curve at 2000Hz freq cf of OTOSCLEROSIS.. . .

can anyone explain y does it appear?? ? ? ?

to understand y it occurs lets see the bone conduction first



BONE CONDUCTION:
sound from the environment r transferred to ear thru vibration of TM(air conduction)
and bone conduction.

bone conduction has TWO ROUTES -->
1) thru vibrations of skull
2) and thru vibraton of ossicles (vibrations of skull secondarily vibrates the ossicles which then transmittd thru round window and ABLE to hear )

normally the 1 & 2 doesnt occur at the same time. there is a time lag. . WHICH RESULTS IN OSSICULAR INERTIA. this is very impt for a bone conduction to be normal

now in otosclerosis foot plate of stapes is fixed. so now the skull and the ossicles are a single unit . ie both vibrates at the same time -
LOSS IN OSSICULAR INERTIA which results in loss of bone conduction in otosclerosis.


but y does it occur only at 2000Hz ??

for every freq a particular str is vibratd (*2) . and for 2000Hz freeq the str vibrated is the foot plate of stapes .

thats y in otosclerosi where v see fixation of stapes foot plate . loss of ossicular inertia ocuurs particularly for 2000hz and the loss is there at 2000Hz resulting in the CAHARTS NOTCH


thnx for hearing the story ..!! hope u understood!!!

i indeed did
good one