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Fat within the thecal sac and associated with the

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spinal cord can be due to a variety of etiologies.

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We can have lipomas of the spinal cord generally

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affecting the thoracic region

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or the filum terminale.

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We can also have lipomyelomeningoceles, in which case

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there is fat associated with

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a spinal dysraphic state.

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When we have selected lipomas,

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they're usually intradural

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in location at 60%, 40% may be extradural, and that

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might occur generally down at the lumbosacral

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junction. As we look at this example to the right,

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we see that there is bright signal intensity on

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the T1-weighted scan, which is the same as the

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subcutaneous fat, and on the T2-weighted scan,

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again, the signal intensity of the lesion is the same

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as the subcutaneous fat. Not only that,

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but on this example, we have something called

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the chemical shift artifact. That's

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this bright area at the edge of the lesion in the

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frequency encoded direction, secondary to the

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presence of the fat and the shift that

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that can occur with the frequency.

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So, this is often seen as a bright area in one

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dimension or a darker area in another dimension,

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which is an artifact, which identifies the

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presence of fat. In this situation,

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we we also appear to have an area

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where there is spinal dysraphism.

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So this is more likely to be

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a lipomyelomeningoceles,

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especially since we see that

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the patient has a low cord.

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We also identify that there is a

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meniscus sign of widened CSF,

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identifying that this is indeed in the intradural

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extramedullary compartment.

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Here is another example.

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In this case, we have a patient who has an

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abnormality at the termination of the spinal cord,

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and clearly, there is an area where there

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is high signal in the cord itself.

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So we see bright signal intensity at the termination

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of the spinal cord followed by this large mass.

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Now, this large mass has areas in which

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there is bright signal intensity on T1-weighted scan

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that is showing suppression on the STIR image, and remains

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bright signal intensity on the T2-weighted fast

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spin echo sequence. So this is fat-containing lesion.

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However, there is an additional area here where there is

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intermediate signal intensity on T1-weighted

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scan, which would not be what we would expect for

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fat, and it's bright also on the STIR image,

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so it's not suppressing like fat.

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This is associated with the tethering of the

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cord, which you see at the L4 level.

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So this is more likely to represent

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a dermoid lesion.

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Dermoids are, again, congenital rests

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that are associated with fat and/or soft tissue

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associated, you know, potentially even hair follicles.

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And this lesion is in the congenital category,

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and it may have a sinus tract which leads outside to

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the skin surface, the so-called dermal sinus tract.

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In this case, we don't see the actual tract.

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You'd want to have the clinicians evaluate the

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patient for any abnormalities

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seen on the skin surface.

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So, this is another of the fat-containing

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lesions of the intraspinal canal.