Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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July 7, 2016
Spinal Cord Arteriovenous Malformation (Type III)
- Background:
- Spinal cord arteriovenous malformations (SCAVMs) are rare and can occur in any spinal segments. When they involve other components from the same metamere, it is referred to as SAMS (spinal arteriovenous metameric syndrome).
- Apart from the spinal cord, the epidural space, bone, paraspinal soft tissues, muscles, subcutaneous tissues, and skin can be involved.
- Most do not involve all metameric tissue elements (> 2 tissues from the same metamera are enough).
- Key Diagnostic Features:
- Intramedullary AVM nidus is seen as prominent flow voids with extramedullary and extraspinal extension (dura, bone, and paravertebral muscles).
- They are large and complex lesions, with primary supply from the segmental artery (ies) of the involved metamere(s) and a large network of secondarily recruited vessels of the adjacent levels.
- Spinal angiogram is the "gold standard" for the complete analysis of the angio-architectural AVM features.
- Differential Diagnoses:
- Type II (intramedullary glomus-type): It is the second most common AVM (after the spinal dural fistula). They are located within the spinal cord. In this type there is a compact intramedullary lesion (glomus), in contrast to more diffuse intramedullary lesion (type III). There is no dural, bony or muscular involvement.
- Type IV (direct extramedullary arteriovenous fistula): It is a perimedullary type located on the ventral or lateral pial surface. These are true fistulae, without an intervening vascular network.
- Hypervascular medullary tumors: When vascular flow voids are present on MR images, spinal hemangioblastoma and other hypervascular tumors, including paraganglioma and metastatic tumors (especially from renal cell carcinomas), should be considered in the initial diagnostic approach. A well-defined enhancing mass is the key for distinguishing spinal hypervascular tumors from AVMs. Spinal cord hemangioblastomas are typically superficial, as they are subpial tumors and are more frequently associated with Von-Hippel Lindau disease. Spinal paragangliomas rarely involve the spinal cord and are usually located at the filum terminale or the conus medullaris.
- Treatment:
- SAMS, in general, have poor prognosis, and treatment is difficult due to the complex angioarchitecture of the lesion(s). The majority are not amenable to surgical or endovascular curative treatment.
- Natural history can be improved by targeted embolization.
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