This tympanogram is seen in:
Flat line is seen on tympanometry in patient with a perforation in tympanic membrane. It is not indicated in cases with a diagnosis of perforation of tympanic membrane. However it can be of help in cases with a suspicion of very small perforation in TM (not clearly visible on otoscopy). Flat line confirms a perforation in Tympanic membrane.
OME
Otosclerosis
CSOM
Osssicular chain discontinuity