<prompt> True about tympanic membrane: PGI Dec 2007Tympanosclerosis with increased complianceOssicular disruption with intact tympanic membrane and increased complianceFluid in middle ear cavity increases complianceOtosclerosis reduces compliance  <response>: Ans. D Otosclerosis reduces compliance Tympanometry Tympanometry is an objective test1, widely used in clinical practice is particularly useful in children. It is based on the principle that when a sound strikes tympanic membrane, some of the sound energy is absorbed while the rest is reflected. A stiffer tympanic membrane reflects more sound energy than a complaint one by changing the pressures in a sealed external auditory canal then measuring the reflected sound energy, it is possible to find the compliance or stiffness of the tympano-ossicular system thus find the healthy or diseased status of the middle ear. By chatting the compliance of tympano -ossicular system against various pressure changes, different types of graphs called tympanogram are: Type - A : Normal Tympanogram Type - As: Compliance is lower at or near ambient air pressure. Seen in fixation of ossicles e.g. otosclerosis or malleus fixation. Types AD- High compliance at or near ambient pressure. Seen in the ossicular discontinuity or thin lax tympanic membraneQ. Type - B :A flat or dome-shaped graph. No Change in compliance with pressure changes. Seen in middle ear fluid or thick tympanic membrane Type - C: Maximum compliance occurs with negative pressure in excess of 100 mm of H20. Seen in retracted tympanic membrane may show fluid in middle earr Fig.: Types of tympanogram 