In this acquired condition, the external auditory canal ends blindly at the bony cartilaginous junction.
A false fundus may develop following a severe injury to the epithelium lining the external ear canal: it occurs if granulation tissue is produced at the isthmus in such quantity that it totally occludes the ear canal and then becomes epithelialized.
The patient usually has a severe conductive hearing loss.
A false fundus is usually recognized when the end of the external canal is closer to the speculum during otoscopic examination than the examiner would normally anticipate.
The false fundus also lacks the normal anatomical landmarks of the tympanic membrane, in particular the handle of the malleus.
Frequently, the fundus shows an abnormal thickness resembling skin, as compared to the normal translucency of a tympanic membrane. In many cases it takes on a characteristic magenta hue.
A computerized tomography scan of the external canal and middle ear is required to determine exactly the location of the false fundus and to assess whether or not there is an underlying cholesteatoma.
These patients should be referred for a specialist assessment, since there is the possibility of entrapped epithelium behind the false fundus, resulting in the development of a cholesteatoma.
The false fundus is seen as an abnormally thick membrane resembling skin located at the isthmus of the external auditory canal.