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So, as you can tell,

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when looking for congenital sensorineural hearing loss,

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we implement MRI scanning largely to identify

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whether or not there is a cochlear nerve.

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The importance of this is that in order to

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get a good result from, for example,

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cochlear implantation,

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you need to have a normal cochlear nerve in order

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to transmit that sound that's being produced

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through the cochlear implant.

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So here's another patient who was evaluated for

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congenital sensorineural hearing loss.

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And again, the first thing I do is I will look at the

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expected location for the endolymphatic sac

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to see whether it's enlarged.

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Enlarged endolymphatic sac or large vestibular

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aqueduct is the most common cause of congenital

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sensorineural hearing loss. In this case,

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we see on the right side the endolymphatic sac.

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And that's a normal size.

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How do we know it's a normal size?

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It's smaller in size than the caliber of

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the semicircular canals adjacent to it.

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On the right-hand side,

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we're just catching a little portion

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of the endolymphatic sac here.

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So it's small in size and not the problem.

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And when we look at the cochlear development,

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once again,

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we see a pretty good-looking basal turn of the

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cochlea with the spiral lamina within it

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separating the endolymph from the peril.

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And as we go up,

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we see a nice-looking modiolus and its separation

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into the middle and apical turns of the cochlea.

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And the same is true on the contralateral side,

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a nice-looking basal turn with spiral lamina,

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nice-looking modiolus, good middle turn,

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good apical turn. So at first blush,

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this looks like pretty good anatomy.

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The vestibule is fine,

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the semicircular canals look fine,

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but we want to look also for the most important

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thing, which is, is there a cochlear nerve?

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And this is nicely demonstrated on

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this axial scan because, again,

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if we start from above and we have very thin

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sections, the section thickness here, as you see,

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we're going from 7.1 to 7.7 mm.

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So, 0.6-millimeter thick slices, so thin sections.

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And as we come from above and we come down to the

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internal auditory canal, we notice two nerves.

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One is anterior; one is posterior.

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So anterior superior is going

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to be our 7th cranial nerve.

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Posterior superior is going to be

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our superior vestibular nerve.

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Let's continue downward to find the other two

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cranial nerves. And in this situation,

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we wonder whether we're getting posteriorly here,

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the inferior vestibular nerve,

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but do we have a good cochlear nerve?

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Let's look on the contralateral side.

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Here we have what appears to be a single nerve

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going more posteriorly into the vestibular system,

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but we don't really see a nerve going anteriorly in

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the inferior portion of the

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internal auditory canal.

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This little thing here that you're seeing

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is likely just CSF pulsation artifact,

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what we see sometimes on these cyst images.

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So this can be better defined on

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our Sagittal reconstruction.

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So here's our Sagittal reconstruction

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and once again, we have the block.

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The two things that are kind of fused together are

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going to be superior and inferior vestibular

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nerve. And we have the nerve superior anterior.

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This is the front of the face,

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the back of the face.

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And so this is our facial nerve,

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but we're not seeing another black thing,

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a cochlear nerve in the internal auditory canal.

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Let's cross the midline and go to the other side.

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And here we see the superior vestibular

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nerve and the 7th cranial nerve,

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and we are missing the inferior vestibular

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nerve and the cochlear nerve below.

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So nothing going to the cochlea here.

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And in this case,

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we don't even have an inferior vestibular nerve.

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So this is the value of high-resolution cyst

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imaging in surgical planning for cochlear

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implantation in children who may have congenital

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sensory neural hearing loss. In this case,

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once again,

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the patient does not have a cochlear nerve

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that will serve to provide the hearing,

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even in a patient who has been implanted.