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What I'd like to do is to provide you with my

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approach to a case of a child who has a

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sensorineural hearing loss. So again,

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once I hear that the patient has

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sensorineural hearing loss,

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I'm more concerned with the inner ear structures

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than I am with the external auditory canal

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or middle ear. So nonetheless,

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my approach is generally to look from outside in.

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So I'm going to be looking at the external

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auditory canal. And in this case,

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we see that the patient actually does have external

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auditory canal hypoplasia. This is small in size, it's stenotic.

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And we note that the helix of the ear is poorly formed.

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So this patient does have external auditory

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canal problems. And as we continue onward,

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we'll start to look into the middle ear cavity.

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The middle ear cavity,

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we're looking at the ossicles, and we're looking for

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our typical ice cream and ice cream cone of the head

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of the malleus and the short process of the incus,

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and then the long process of the incus as these two

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parallel lines communicating with the stapes

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at the incudostapedial joint.

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And here we have the crura of the stapes.

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Here is the posterior crus,

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here's the anterior crus

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identified as it comes to the oval window.

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So having looked through the external ear,

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identifying the stenosis,

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and then the middle ear ossicles,

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which look actually pretty good,

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we'll then concentrate on the inner ear structures.

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Now, I know that the most common cause of congenital

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sensorineural hearing loss is

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a problem with enlargement of the vestibular aqueduct.

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So one of the things I'm going to be looking at is

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this vestibular aqueduct and making sure that it is

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smaller in size than the caliber

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of the semicircular canals.

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So although this is the most common abnormality

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for congenital sensorineural hearing loss,

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it is normal in this particular case.

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So now we will concentrate on the vestibular

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system and the cochlear system.

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So here is our internal auditory canal.

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We notice that the internal auditory

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canal is actually of a normal size.

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If I see a narrow internal auditory canal,

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it's more likely that a patient has cochlear nerve

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aplasia or an abnormality associated with it.

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So we're going to check the caliber of the internal

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auditory canal, in this case, normal.

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And we're actually seeing the crista falciformis

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or the separation of the internal auditory canal.

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This is the facial nerve coming across.

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And then we have our tympanic.

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So the facial nerve looks normal.

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As we look at the cochlea, however,

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we identify that we don't have the

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normal turns of the cochlea.

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We have a basal turn, and then we have this little

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nubbin of something that should be developed

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into the middle and apical turn, but is not in this individual.

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So we're just seeing the basal turn of the cochlea.

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We see the round window,

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and its opening to the basal turn,

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but nothing that well-developed in the cochlea here.

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The vestibule, on the other hand,

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we see nicely, and we see a lateral semicircular canal.

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And we start to see the superior semicircular canal

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and the posterior semicircular canal.

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So this is an isolated cochlear hypoplasia.

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We've got the basal turn, but that's about it.

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So the next thing we want to do

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is to check the other side.

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Is this a bilateral process or is it a unilateral process?

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Again, most of these cases, you have bilateral

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sensory neural hearing loss,

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because whatever insulted the development

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of one side will often insult the other.

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So let's look at the same anatomy.

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Here we come to the superior semicircular canal,

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the posterior semicircular canal.

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We come to the vestibule with the lateral

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semicircular canal. And as we look for the cochlea,

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we once again see a basal turn and

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then a little nubbin of the

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remainder of the cochlea.

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We really don't have a modiolus.

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We don't have an internal skeleton,

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because all we have is this one turn of the cochlea.

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And here's the round window niche.

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Let's look at the internal auditory canal on

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this side. It looks relatively normal.

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So the next step in trying to guide the clinicians

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on what to do about this case is to make sure that

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we can identify an actual cochlear nerve.

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For that,

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we turn to the high-resolution T2-weighted FIESTA

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or CISS or turbo field echo scanning with T2-weighted.

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So let's look at the raw data here.

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These are the axial raw data of the FIESTA sequence.

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And we see nicely the vestibule and the semicircular

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canal, the lateral semicircular canal.

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We have the posterior semicircular canal.

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We have the portions of the superior semicircular

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canal up above here coming together.

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So what about the cochlea?

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So, once again,

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we're seeing just a funny-looking single

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turn of the cochlea bilaterally.

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And now we have to look for the nerves.

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So on the axial plane, when we're up here,

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superior to the internal auditory canal,

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and then move further down,

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we see two structures that are going to the superior

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portion of the left internal auditory canal.

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Let me magnify this and see whether we

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can point this out a little bit.

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Oh, that's nice.

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We're just going to stick with the left-hand side.

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So here we see two nerves that are going to the

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superiormost portion of the internal auditory canal.

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Well, we know superior anterior seven up is going

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to be the 7th cranial nerve, the facial nerve.

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Superior posterior is going to be the superior

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vestibular nerve. Let's go further inferiorly.

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When we go further inferiorly,

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we see only one nerve.

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And this one nerve is in the posterior portion

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of the internal auditory canal.

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This is the inferior vestibular nerve,

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but we are not seeing a cochlear nerve.

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So you don't see something go towards that cochlea.

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This is superior, this is facial nerve.

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But as we go inferior,

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we're only seeing one nerve in

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the internal auditory canal.

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We can do a reconstruction in an oblique plane and

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look for the cochlear nerve in the oblique plane.

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So here,

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as we go towards the internal auditory canal,

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I'm going to magnify this.

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And here's our internal auditory canal.

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And what we see in the internal auditory canal are

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the superior and inferior vestibular nerves.

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They often are not well separated,

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despite our planes of section

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and our high resolution.

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You see them sometimes together. You see another

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nerve, superiorly and anteriorly,

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which is your 7th cranial nerve.

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But right here,

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where we should be seeing an additional nerve,

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the cochlear nerve, which is anterior and inferior,

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we're missing it.

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So here's the one that's going anterior superior,

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the facial nerve.

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Here are the two that are posterior,

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the vestibular nerves.

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But where is the cochlear nerve?

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In this case,

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it's a missing cochlear nerve in a patient

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who has cochlear hypoplasia.