Carha's notch in audiometery is seen in:
Carhas notchBone conduction is normal in otosclerosis.In some cases there is a dip in bone conduction curve which is maximum at 2000 Hz / 2 KHZ called as Carhas notch.Carhas notch is seen only in bone conduction curve.It disappears after successful stapedectomy/stapedotomy. The reason why it disappears after successful surgery is that when the skull is vibrated by bone--conduction sound, the sound is detected by the cochlea 3 routes:- Route (a)--is by direct vibration within the skull.- Route (b)--is by vibration of the ossicular chain which is suspended within the skull.- Route (c)--is by vibrations emanating into the external auditory canal as sound and being heard by the normal air-conduction route.In a conduction type of hearing loss (as in otosclerosis) the latter two routes are deficient but regained by successful reconstruction surgery. Hence bone conduction thresholds improve following surgery.
Ocular discontinuity
Haemotympanum
Otomycosis
Otosclerosis