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After cavernomas, duro-arteriovenous fistulas are

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the most common of the vascular malformations,

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the true vascular malformations

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of the spinal canal.

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By dural, we mean that there is a fistula that is

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occurring in the nerve root's sleeve

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outside the spinal canal.

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These are often considered epidural extradural lesions,

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rather than intradural extramedullary lesions.

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However, because there is venous hypertension associated

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with the dural arterial-venous

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malformation...

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fistula, you find that the cord signal becomes bright.

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So, the cord signal is secondarily bright due to

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venous congestion associated with the extradural

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arteriovenous fistula. In addition,

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in the intradural extramedullary space,

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you find dilated veins.

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So, here on this T2-weighted scan,

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we see the dilated veins of drainage from

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the dural arteriovenous fistula.

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We see the high signal intensity in the spinal

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cord from the venous congestion.

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The French term that is used

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for this is "Foix-Alajouanine"

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and it does cause a myelopathy due to that

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venous congestion. On rare occasions,

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you can get venous ischemia and a venous

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infarction from dural arterial venous fistulas.

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This is another case again where you see all

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of these markedly enlarged blood vessels.

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But the markedly enlarged vessels

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are not within the spinal cord,

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they're outside the spinal cord in the

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intradural extramedullary space. However,

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you do see bright signal intensity on T2-weighted

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scan in the spinal cord from

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the venous congestion.

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This is a diagram from the article by Spetzler

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in which he identifies the arterial venous

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fistula in the nerve root sleeve

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in the extradural space.

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And you see the enlarged veins on the surface

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of the spinal cord occurring,

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which may be associated with the congestion of

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the spinal cord and the patient's myelopathy.

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This is a disease entity that typically occurs

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in elderly men, and the patient will

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present with a long history,

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months-long history of myelopathic symptoms.

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And this is your type I spinal arteriovenous fistula.

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This is a type II spinal arteriovenous malformation.

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This is in Spetzler's classification,

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a true AVM in which the fistula is occurring

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within the spinal cord.

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So this is an intradural intramedullary

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arteriovenous malformation.

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The previous case is an extradural fistula with

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venous congestion and myelopathic symptoms.

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But the AV,

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the arteriovenous malformation

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is not in the spinal cord.

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So this has an intramedullary nidus. This is

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your type II arteriovenous malformation.

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It still has enlarged veins outside the spinal

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cord in the intradural extramedullary location.

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Here's a catheter angiogram in which

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one sees the vascular malformation,

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which is within the spinal cord with draining

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veins, as well as feeding by the

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anterior spinal artery.

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You can see on this lateral view, there's the

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vertebral body here, vertebral body here,

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vertebral body here that the vascular malformation is

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within the spinal cord, and on the AP view,

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it is also within the spinal cord.