Tympanometry

Eardrum mobility test for middle ear function

Overview

Tympanometry is an objective test of middle ear function. A probe sealed in the ear canal varies the air pressure while measuring how readily the eardrum and middle ear accept sound energy, known as compliance or admittance. Results are plotted as a tympanogram. A Type A curve indicates normal mobility, a flat Type B curve suggests fluid behind the eardrum or, with a large ear canal volume, a perforation or open ventilation tube, and a Type C curve with its peak at negative pressure suggests Eustachian tube dysfunction. Shallow or unusually tall peaks can point to stiffening, as in otosclerosis, or to a flaccid eardrum or ossicular discontinuity. Because it needs no behavioural response and takes only seconds, it is widely used to detect glue ear in young children. Combined with acoustic reflex testing it forms the immittance battery, which helps locate problems in the middle ear, cochlea, auditory nerve, brainstem, and facial nerve.