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Accessory Nerve – Cranial Nerve XI

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Dr. P here to talk about the spinal accessory

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or accessory nerve, nerve number eleven.

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It's a cranial nerve that supplies the

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sternocleidomastoid and trapezius muscles,

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and it's considered the 11th of twelve

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pairs of cranial nerves.

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It was formerly believed to originate in the brain,

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but that's no longer really accepted dogma.

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As you know,

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the sternocleidomastoid muscle

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tilts and rotates the head,

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while the trapezius muscle connected to the

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scapula acts in shoulder shrugging.

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So here we have an axial image level of the pyramid

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and restiform body.

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That's a vessel right there.

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There's your glossopharyngeal nerve right there.

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Here is your vagus nerve.

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And right behind that,

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this little reit, or complex posteriorly,

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the third of these three nerves,

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A, B and C, right there,

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is the lowermost portion of the spinal accessory nerve.

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Now, the spinal accessory nerve

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has traditional descriptions that divide it up

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into a spinal part and a cranial part.

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The cranial component rapidly joins the vagus nerve,

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so there's some debate about whether the cranial part

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should actually be considered part

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of the spinal accessory nerve.

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And we're going to get into those two

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major contributions, one up higher,

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one down lower in the sagittal projection,

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in the next vignette.

Report

Description

Faculty

Stephen J Pomeranz, MD

Chief Medical Officer, ProScan Imaging. Founder, MRI Online

ProScan Imaging

Tags

Neuroradiology

MRI

Brain

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