Welch Allyn MicroTymp 3 portable tympanometric instrument - User Manual - Manual (Page 59)

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Middle ear pathologies
Low-admittance pathologies
Otitis media with effusion (OME)
Otitis media with effusion (OME) is an inflammation of the middle ear accompanied by an
accumulation of fluid. Fluid in the middle ear can cause conductive hearing impairment
when it interferes with the normal vibration of the eardrum by sound waves. In advanced
cases, OME results in flat tympanograms (low Peak Ya). In intermediate stages of OME,
the peak height may be normal, but the gradient may be widened.
Middle ear tumor
A wide variety of neoplastic processes exist that invade the middle ear. The most
common is the keratoma (cholesteatoma), a collection of keratinizing squamous
epithelium that frequently originates from Shrapnel's membrane (pars flaccida) of the
tympanic membrane or the ear canal wall and invades the middle ear space. Other middle
ear tumors include the cholesterol granuloma, glomus tumor, and squamous cell
carcinoma. These pathologies generally result in a flat tympanogram.
Lateral ossicular fixation
Lateral ossicular fixation may result from tympanosclerosis, a complication of chronic
otitis media that may involve the eardrum, malleus, incus, and/or stapes. In general, the
more lateral the fixation, the more effect the condition has on the tympanogram. Lateral
fixations typically cause low Peak Ya and wide tympanometric widths.
Otosclerosis
Because the otosclerotic lesion is more medial than lateral ossicular fixation, the
tympanogram is less affected. The tympanometric shape is often indistinguishable from
normal, although the Peak Ya may be slightly low and the tympanometric gradient (width)
may be narrower than the normal tympanogram.
Tympanic membrane abnormalities
The tympanic membrane is normally a stiff, conically-shaped structure that derives its stiff
characteristic from the lamina propria, a layer of connective tissue that is situated
between the outer layer of squamous epithelium (skin) and the inner layer of mucous
membrane. When the eardrum heals after a relatively large perforation, the lamina propria
may be absent or thin in the region of the scar. This neomembrane can be set into