A lady has B/L hearing loss since 4 years which worsened during pregnancy. Type of impedence auditometry graph will be :
Ans. is 'b' i.e. As Bilateral painless hearing loss in 25 yr old female accentuated with pregnancy is suggestive of otosclerosis or otospongiosis Tympanometry shows as curve due to ossicular stiffness. Tympanometry Is based on the principle of reflection of sound energy when sound strikes tympanic membrane, some of the sound energy is absorbed while the rest is reflected. A stiffer tympanic membrane would reflect more of sound energy than a compliant one. By changing the pressures in a sealed external auditory canal and then measuring the reflected sound energy, it is possible to find the compliance or stiffness of the tympano-ossicular system and thus find the healthy or diseased status of the middle ear. By charting the compliance of tympano-ossicular system against various pressure changes, different types of graphs called tympanograms are obtained. These tympanograms are diagnostic of certain middle ear pathologies. Types of tympanograms Type A Normal tympanogram Type As Reduced compliance at or near ambient air pressure. Seen in fixation of ossicles, eg. otosclerosis or malleus fixation. Type Ad Increased compliance at or near ambient pressure. Seen in ossicular discontinuity or thin and lax tympanic membrane. Type B Flat or dome shaped graph. Seen in middle ear fluid or thick tympanic membrane. Type C Maximum compliance at pressures more than -100 mm H20 (negative pressure in middle ear) eg. eustachian tube obs truction or early stage of serous otitis media.
Ad
As
B
C
Otosclerosis