Background and Objectives :Ossicular disruptions following trauma can occur without perforation of the tympanic membrane. It is difficult to confirm the presence of ossicular disruption in such cases. We have reviewed the clinical characteristics
of
patients with traumatic ossicular disruption with an intact tympanic membrane, and purposed a new diagnostic flow chart that utilizes three-dimensional CT scanning. Materials & Methods: Twenty patients who had ossicular disruption with an intact
tympanic membrane that was confirmed by exploro-tympanotomy were studied. In two cases where the ossicular chain appeared intact on conventional temporal bone CT, a three-dimensional CT scan was performed. Results: Concomitant temporal bone
fracture was
not found in 60% of the patients, and only eleven patients showed an Ad-type tympanogram. The most common site of disruption on preoperative temporal bone CT scans was the
incudostapedial joint, but exploro-tympanotomy revealed that dislocation
of the incus was the most common. The temporal bone CT scans of five
patients appeared normal, but the three-dimensional CT scan performed
on two of these patients exhibited evidences of ossicular disruption.
Conclusion: The diagnosis of ossicular disruption with an intact
tympanic membrane can be made through a history of head trauma,
audiologic studies(pure tone audiometry, impedance audiometry), and
temporal bone CT scans. However, diagnosis may occasionally be difficult
with these modalities, and three-dimensional CT scanning can be helpful
in such cases.
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