The subtypes below (1-4) are based on the Anson and Spetzler Classification from their 1992 article
http://emedicine.medscape.com/article/248456-overview
see also
http://www.medschool.lsuhsc.edu/neurosurgery/nervecenter/spavm.html
1 dural AVF
2 glomus: discreet intramedullary AVM
3 juvenile: Intramedullary with extramedullary component (Cobb syndrome/metameric)
4 pial AVF (intradural extramedullary)
This appears to be the basis of the Core Exam Categories below
Of course real life includes other vascular lesions:
Epidural fistula in the lumbar region
In 2002 Spetzler modified this classification. One of the controversial aspects of this revision is that they added cavernomas and hemangioblasotomas as neoplasms.
Reference:
Historical Review
Neuroradiology greatly advanced the understanding of the various vascular pathologies.
http://www.medscape.com/viewarticle/554871_4
Fascinoma Case Report
46 yo woman with myelopathy aggravated by menstruation