Interactive Transcript
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As I mentioned,
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the enlarged vestibular aqueduct syndrome, or EVAS,
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on CT, is analogous to the enlarged endolymphatic
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sac. You actually see the sac on the MRI scan,
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and this is the most frequent finding in general
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sensorineural hearing loss. Now,
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we've seen examples in the incomplete
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partition type two,
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where it is so associated with abnormal
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malformation of the cochlea. However,
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it may be an isolated finding,
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and it is an abnormality,
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which is typically bilateral, we say,
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in 90% of cases and occurs in
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females more so than males.
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So isolated endolymphatic sac enlargement is an
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anomaly that may be associated with congenital
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sensorineural hearing loss,
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but it also may be seen in conjunction with abnormal
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development of the cochlea in our incomplete
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partition type 2. Here's a CT scan,
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bilateral involvement with enlargement
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of the vestibular aqueduct.
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Here is what we might see on MRI scan.
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On the MRI scan in this individual,
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you see that there is a high signal intensity
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abnormality on our T2 CISS image,
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and this represents the enlarged vestibular
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aqueduct, or endolymphatic sac.
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So we're actually seeing the sac.
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Again, the aqueduct we usually refer to in the CT,
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whereas in MR we're seeing the sac,
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the endolymphatic sac. And these are dilated.
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How do we know they're dilated?
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They're larger in caliber than the semicircular
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canals when we compare to them.
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