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.
Stephen J Pomeranz, MD
Chief Medical Officer, ProScan Imaging. Founder, MRI Online
ProScan Imaging
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