AAO-HNSF Primary Care Otolaryngology Handbook

CHAPTER 5

TM is intact, and middle ear pressure equals atmospheric pressure. Type B tympanogram is flat without a peak and indicates no drum mobility; either the middle ear is filled with fluid, or the TM has a perforation. These two conditions can be differentiated by examining the volume read by the impedance bridge. Middle ear fluid will generate normal volumes, while TM perforations will generate large volumes. Type C tympanograms (peak eardrum mobility when pressure is subatmospheric) indicate a retracted TM secondary to Eustachian tube dysfunction. Tympanometry results can help detect middle ear fluid when the physical exam is unclear. Conductive Hearing Loss Careful physical examination of the ear with the aid of a microscope, tuning fork testing, and audiometric testing can frequently determine the cause of a conductive hearing loss. Most causes of conductive hearing loss can be medically or surgically corrected. We can help improve or even resolve the hearing loss with treatment and without use of hearing aids. Swelling of the EAC caused by otitis externa can be treated with appropriate topical ear drops. Cerumen impaction can be cleaned with cerumenolytic irrigations (e.g., hydrogen peroxide) or specialized instruments. Middle ear fluid , the most common cause of hearing loss in chil- dren, can be treated with myringotomy tubes if the fluid has been present for more than three months, and TM perforations can be surgically repaired.

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Figure 5.2. Three tympanograms demonstrating change in compliance of the middle ear (vertical axis) with changes in ear canal pressure. Type A is normal, with the greatest compliance at the point where the pressure in the ear canal is equal to that of atmospheric pressure (peak is at 0). Type B demonstrates very poor compliance at any frequency, suggestive of a TM immobilized by fluid in the middle ear or a TM perforation (no peak). Type C represents a tympanogram in which the compliance of the membrane is greatest at a point where the pressure in the canal is 200 decapascals below that of atmospheric pressure (peak shifted to the left). This suggests poor Eustachian tube function with persistent negative pressure in the middle ear.

Primary Care Otolaryngology