9. DIAGNOSIS OF AUDITORY DISORDERS
9.1 DISORDERS AND THEIR SYMPTOMS
9.1.1
MIDDLE-EAR FLUID AND EFFUSION
Serous otitis is a disease which can lead to a build-up of fluid and a re-
duced pressure in the middle ear. The resulting middle ear dysfunction
with fluid effusion in the middle ear space produces a very shallow tym-
panogram with a reduced static compliance and a reduced gradient.
Only in a small proportion of cases is a peaked tympanogram produced.
The pressure reduction results in a tympanogram shifted to the left. Ipsi-
lateral acoustic reflex is often absent.
9.1.2
DISRUPTION OF THE OSSICULAR CHAIN
If there is a discontinuity in the ossicular chain, the impedance of the
cochlea and oval window will have little or no influence on the imped-
ance of the eardrum. Disruption of the ossicular chain results in a very
tall tympanogram with increased static compliance and increased gradi-
ent, or, in some cases, multiple “humps”.
If an ipsilateral reflex is detected, then the disruption is likely to be
downstream of the hammer. Otherwise, the reflex may be absent.
9.1.3
OTOSCLEROSIS
Otosclerosis and relative fixation of the footplate of the
stapes
tend to re-
sult in reduced static compliance (0.2 to 0.4), reduced gradient, and in-
creased tympanogram width. Reflex may be reduced or absent.
9.1.4
PERFORATED EARDRUM
The eardrum may be perforated as a result of trauma or because it has
atrophied. The tympanogram will be almost completely flat.
9.1.5
OCCLUDED EUSTACHIAN TUBE
If the Eustachian Tube is occluded (blocked), or fails to open regularly
(dysfunction), the pressure in the middle ear will usually become less
than atmospheric pressure. The effect will be to shift the tympanogram
to the left. The reflex is normally unaffected. If the eardrum is not perfo-
rated, this condition may be investigated using the Intact Eardrum test
Operation Manual
81
GN Otometrics
DIAGNOSIS OF AUDITORY DISORDERS
Chap. 9
ZODIAC 901 Middle-Ear Analyzer
DISORDERS AND THEIR SYMPTOMS
9.1
Содержание Madsen ZODIAC 901
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