Abstract
Objective
The purpose of this study was to determine whether external and internal defects in microtia are related.
Method
Magnetic resonance images of the eustachian tube cartilage were evaluated for 20 patients who had unilateral microtia. Nineteen patients were classified as Grade 2, and one was classified as Grade 3. The Grade 3 patient also had unilateral facial palsy.
Results
On T1-, T2-, and proton-density-weighted images, the eustachian tube cartilage was clearly identified as a pair of straight lines with low signal intensity. There was no evidence of hypoplasia of the eustachian tube cartilage on the microtic side in any Grade 2 patient, but hypoplasia was evident on the microtic side of the patient classified as Grade 3.
Conclusion
These findings are consistent with the view that impairment of embryonic development before 6 weeks results in injury to the immature pri-mordium and malformation of both the external and middle ear. In contrast, injuries that occur at a later fetal age (i.e., after 3 months) do not appear to cause middle ear malformations.
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