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Thus far,

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we've focused mainly on the cochlear portion of

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the cochlear vestibular cystic malformation.

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And the reason why is because those patients with the

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cochlear malformation are the ones that are presenting

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with congenital sensory neurohearing loss.

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Now, you can have a

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cochlea that is relatively normally developed

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and yet have vestibular abnormalities.

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Although they are developing at the same time,

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they may be differentially affected by whatever the

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congenital infection or drug-related insult to the

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development of these inner ear structures.

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This is an example of a patient who has relatively

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normal appearance to the cochlea but has abnormalities

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bilaterally in the vestibule.

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So here we have a CISS MRI scan,

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and we look at the cochlea and we say,

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well, this is a pretty good-looking modulus.

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We have a pretty good-looking basal turn and spiral lamina.

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We have a pretty good-looking middle turn,

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and we have a pretty good-looking apical turn.

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So here's one the middle turn, the apical turn,

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and the basal turn,

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all in the same section with the lines of separation.

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However,

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when we look at the associated vestibule,

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we see that the vestibule is markedly dilated

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and one does not have normal development

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on the left side of lateral semicircular canals,

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you have a posterior semicircular canal and a superior

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semicircular canal that are relatively

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normally developed.

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But this lateral semicircular canal basically doesn't

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have the normal bone island between the vestibule and

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the lateral semicircular canal on the left side.

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On the right side,

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we at least are able to identify the vestibule,

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and we're able to see two limbs of

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the lateral semicircular canal.

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But note that they never come together

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laterally, and so they're incompletely formed.

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Yet the patient has a pretty good-looking posterior

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semicircular canal as well as

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superior semicircular canal.

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Posterior and superior semicircular canals seen there

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cochlea, normal development, normal spiral lamina.

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So these are isolated vestibular

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utricular abnormalities,

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worse on the left side than the right side.

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Do they have hearing loss?

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They may have hearing loss,

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but one would expect that the real issue in this

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patient would be balance and in the vestibular system,

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more so than the auditory system.