Abstract
Causal factors of wide shape tympanogram were investigated using a Madsen ZO-72 impedancemeter. Although a wide shape may be recognized in each type (A, AD, As, and C), only wide A and wide AD type were analyzed in this study. Wide A type, whose relative pressure gradient is below 0.15, was found in patients with middle ear effusion and posttympanoplasty, and in normal infants. Soft, hypermobile external auditory meatus with a relatively hypomobile eardrum due either to thickening or effusion, along with a large equivalent volume of the external ear canal, may contribute to form a wide A tympanogram. On the other hand, eardrums of the patients with wide AD tympanogram were partially hypermobile due to an atrophic scar, where we found adhesion of the tympanic membrane around the incudostapedial joint.
