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The Swallow Tail Sign

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Let's take an axial midbrain specimen

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in our discussion of classic PD.

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We'll start on the viewer's left

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where we have the red nucleus.

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And actually, the red nucleus is right

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up against the substantia nigra.

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So, these have already started to bleed together.

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But we do see a linear area of

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iron staining that is brown,

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that has a relatively delicate appearance to it,

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something like this.

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Sometimes you'll see more than one,

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very reminiscent of the tail of a swallow.

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Now,

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this particular example was not completely normal

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as we don't have a nice stripe between our red

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nucleus and our substantia nigra

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over here on the right,

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we've lost the normal definition of the red nucleus,

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which is a more advanced example

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or case of Parkinson's disease.

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And then look at the attenuated appearance or loss

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of staining along the lateral aspect of the

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substantia nigra.

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There,

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and also peripherally there.

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We've lost our little linear delicate area

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of staining along the margin free edge.

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And a lot of times, in Parkinson's disease,

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what you'll see is the substantia nigra very

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intense and low signal here,

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variable in the middle and then fades away on the

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outside and then comes to a blunt end

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as opposed to having this wispy,

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fading away, swallow tail side.

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Let's look at an MRI example with some

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diagrams of the swallow tail.

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There it is seen diagrammatically.

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There's the swallow with the tail.

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There's the magnified view of the substantia

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nigra with the lateral swallow tail appearance

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as opposed to the fat, short,

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blunt-ended appearance of the substantia nigra

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with hyper-concentration medially that

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you'll see in Parkinson's disease.

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The other sign of Parkinson's disease,

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neither of which is specific, by the way,

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loss of the swallow tail sign or bleeding of the

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red nucleus into the substantia nigra

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so that the two become inseparable.

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Neither of those signs are specific

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for Parkinson's disease.

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But in mid to late-stage Parkinson's disease,

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the absence of both of them would mitigate strongly

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against the diagnosis of classic PD.

Report

Description

Faculty

Stephen J Pomeranz, MD

Chief Medical Officer, ProScan Imaging. Founder, MRI Online

ProScan Imaging

Tags

Syndromes

Neuroradiology

MRI

Drug related

Brain

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