Vascular Malformations of the Spinal Cord

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• Spinal dural arteriovenous fistula (SDAVF)

• Spinal cord arteriovenous malformation (SCAVM)

• Spinal cord (intradural or perimedullary) arteriovenous fistula (SCAVF)

• Cavernous malformation (CM)

Spinal dural arteriovenous fistula (SDAVF): Head

Pathology: This is an AV shunt that occurs within the dural covering of the spinal cord with the arterial supply usually arising from a dural branch of radicular artery. An intradural vein drains the shunt directly into the pial veins of the cord leading to venous engorgement and venous hypertension that may lead to a venous hypertensive myelopathy. The chronic effects are believed to result in a "subacute necrotizing myelopathy" identical to that described by Foix and Alajouanine in 1926.

Incidence: They represent at least 35% of all spinal vascular malformation and are believed to be an acquired condition resulting from thrombosis of the extradural venous plexus.

Location and presentation: They are usually tiny; seen most commonly in between level T5 and L3; and usually locate adjacent to the intervertebral foramen. Most commoly prsents as chronic myelopathy.

Spinal cord arteriovenous malformation (SCAVM): Head

Pathology: This is believed to be a congenital lesion. Most patients present in their second through fourth decade. The nidus of the SCAVM is located on or within the parenchyma of the spinal cord itself with arterial supply from vessels that also directly supply the cord, that is the anterior and posterior spinal artery. Feeding artery aneurysm is common due to the high flow nature of SCAVM. The glomus subtype is characterized by a relatively compact nidus. The much less common juvenile subtype, there is additional extramedullary and often extraspinal extension. Adverse effects of SCAVM include stealing of blod from normal neural tissue leading to ischemia, venous hypertension, thrombosis, and, most often, hemorrhage.

Location and presentation: most common in the cervical and thoracolumbar region but may be seen in any level including the filum terminale. Acute hemorrhage is a common presentation.

Spinal cord (intradural or perimedullary) arteriovenous fistula (SCAVF):

Pathology: SCAVFs consist of direct arteriovenous fistulas located on the cord and fed directly by arteries supplying the cord, most frequently the anterior spinal artery. The indural location of the shunt, constant involvement of arteries supplying the spinal cord, and lack of intervening nidus are angioarchitectural features that differentiate SCAVF from both SDAVF and SCAVM.

Incidence and presentation: Represent about 8%-19% of all cases. They are believed to be congenital lesions. Patients present most commonly in their second through 4th decade and the most common neurologic presentation is progressive asymmetrical radiculomedullary isgns involving the lower extremities. Hemorrhage is also common.

Location: Lower thoracic and lumbar region.

Cavernous malformation (CM): Head

Pathology: Unlike the AVMs and AVFs, CMs are malformations without high flow AV shunts. Cauda equina and filum terminalis can also be involved. Histology is similar, if not identical, to their counterparts in the brain.

Location and presentation: They are intramedullary and affect the whole spinal cord. Patients most commonly present with discrete episodic neurologic dysfunction with variable recovery between episodes. Monophasic acute or chronic deterioration of spinal cord function may also occur. The acute symptomatology is probably secondary to hemorrhage.

NeuroLearn NeuroHelp Vascular  For Comment: KarMing-Fung@ouhsc.edu