Spinal vascular malformations are rare but knowledge of them is important as if undiagnosed and untreated they can lead to serious complications. The main types are arteriovenous fistulae, arteriovenous malformations, cavernous malformations, and capillary telangiectasia.
Pathology
Classification
Many classifications for spinal vascular malformations have been proposed without a clear consensus nomenclature. Notably, much of the older literature described all arteriovenous shunting lesions as arteriovenous malformations (AVM), but newer classifications have distinguished arteriovenous malformations from arteriovenous fistulas (AVF) 13.
Spinal arteriovenous shunts ("malformations") have classically been categorised in a numbered system, although over time the names for each have changed and additional categories and subcategories have been proposed 9-13:
- type I: dural AVF
- type II: intramedullary glomus AVM
- type III: intramedullary juvenile AVM
- type IV: perimedullary AVF
- type V: extradural AVF
Spetzler et al. proposed the following categories of spinal cord vascular malformations 3,5:
-
arteriovenous fistulas (AVFs)
- intradural
- dorsal (formerly "type I")
- single feeder (type A)
- multiple feeders (type B)
- ventral (formerly "type IV")
- small shunt
- medium shunt
- large shunt
- dorsal (formerly "type I")
- extradural
- intradural
-
arteriovenous malformations (AVMs)
- intradural
- intramedullary (formerly "type II")
- compact
- diffuse
- intramedullary (formerly "type II")
- extradural–intradural (formerly "type III")
- conus medullaris
- intradural
- neoplastic vascular lesions
- spinal aneurysms
The Bicêtre group classified spinal cord arteriovenous shunts into 3 aetiologic categories 4:
- genetic hereditary lesions (such as hereditary haemorrhagic telangiectasia)
- genetic nonhereditary lesions (multiple lesions with metameric or myelomeric associations, such as Cobb syndrome, Klippel-Trenaunay syndrome, and Parkes Weber syndrome)
- single lesions (which may reflect incomplete expression of the above two categories but represent the majority of spinal vascular malformations)
Krings et al. noted that spinal vascular malformations can be distinguished by their vascular anatomy into dural and pial arteriovenous shunting lesions and cavernous malformations, analogous to brain vascular malformations 2,6. The main types are as follows:
- dural arteriovenous fistulae (DAVF; 70% of all spinal arteriovenous shunts)
-
arteriovenous malformations (AVM)
- fistulous (perimedullary fistula type) AVM
- glomerular (plexiform or nidus-type) AVM
- juvenile AVM
- cavernous malformation
Patsalides et al. classified spinal vascular lesions topographically 1:
- arteriovenous lesions
-
arteriovenous fistula (AVF) (direct shunt between artery and vein)
- pial AVF (type IV, spinal cord AVF, ventral intradural AVF, or perimedullary AVF)
- small
- large
- giant
- dural AVF (type I, dural intradural AVF)
- epidural AVF (type V, extradural AVF)
- pial AVF (type IV, spinal cord AVF, ventral intradural AVF, or perimedullary AVF)
-
arteriovenous malformation (AVM) (nidus between artery and vein)
- intramedullary AVM (type II, glomus-type AVM)
- pial AVM
- epidural AVM
- intra- and extramedullary AVM (type III, intradural-extradural, juvenile AVM, or metameric AVM)
-
arteriovenous fistula (AVF) (direct shunt between artery and vein)
- lesions without arteriovenous shunting
Several spinal vascular malformative lesions have not been featured in the above classifications:
- vertebral haemangioma
-
epidural haemangioma 7
- arteriovenous type
- venous type
- cavernous type
- cavernous type with haematoma
- intradural extramedullary capillary haemangioma 8