Neurosurgery notes/Intradural (pial) ventral AVF

Intradural (pial) ventral AVF

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Spinal AVF
RAG
RAG
MCQ
MCQ
Last edited time
Jul 13, 2026 07:06 PM GMT+0

General

  • Aka
    • Perimedullary fistula,
    • Pial arteriovenous fistulae
    • Fistulous spinal cord AVM (SCAVM)
    • Di Chiro IV

Connection

  • A pial AV fistula: Direct connection between (connection on pial surface)- The fistulation is intradural but extramedullary
    • Pial artery (Anterior spinal artery/radiculopial artery/radiculomedullary artery) ↔
    • Medullary or radicular vein/venous plexus
  • Not a spinal dural fistula
    • Because
      • Dural fistulas form in the dura (usually in the nerve root sleeve, although Spetzler insisted on a subarachnoid location just within the nerve root sleeve) and
      • DO NOT involve arteries that supply the spinal cord.
      • The dural fistula becomes symptomatic as a result of spinal venous congestion, and not because the fistula directly involves a spinal cord artery.
  • Not an AVM,
    • Because AVMs have a nidus, and a fistula does not
    • It is sometimes difficult to tell even on angiography whether or not a nidus exists — tortuous veins can look a lot like a nidus.
    • Intradural fistulas range from single artery-to-vein connection to increasing arterial feeder complexity.
      • This complexity is likely related to regional peri-fistulous anatomy dictating availability of additional arterial contributors, the size of fistula, and its duration of existence.
      • However, meticulous microcatheterization does answer these questions and so ultimately intradural fistulas can be separated from AVMs by superselective spinal angiography.
  • Vein becomes arterialized and is readily recognized as it penetrates the dura just caudal to the exiting nerve root
  • Same AVF but increasing complexity as the arterial side recruits more adjacent vessels to supply the fistula: (Left to right)
    • Anterior spinal artery
    • Anterior spinal artery + ipsilateral Radiculopial artery
    • Anterior spinal artery + ipsilateral Radiculopial artery + Contralateral Radiculopial artery
  • Looks more like an AVM as it gets more complex but there is only one connection and no Nidus
  • The radiculopial artery is a safer embolization route than anterior spinal artery
  • This corresponds to the subtype
    1. Single feeder (Artery of Adamkiewicz), slow flow, moderate venous enlargement
      • Treatment
        • Surgery
        • Endovascular techniques are difficult with these lesions due to the small size of feeding vessels hence surgical excision is often mandated.
    2. Multiple feeders, intermediate flow, more dilated veins
      • Marked venous enlargement.
      • Treatment
        • Embolization in these lesions is easier, due to the increased size of feeding vessels.
        • In cases of incomplete shunt obliteration with an endovascular approach, direct surgical excision may be necessary.
    3. Giant, multiple-feeder, high-flow shunt with dilated tortuous veins
      • Spinal ischemia may develop in these lesions secondary to vascular steal.
      • Treatment
        • Combination of endovascular ablation → surgical excision of retained elements.
        • Surgery alone is technically difficult and may jeopardize the spinal cord.
          • Due to the size of these lesions
      Type A
      Type B
      Type C
      Feeder
      Single (artery of Adamkiewicz)
      Multiple
      Giant (large)
      Flow
      Slow
      Moderate
      High
      Veins
      Moderate enlargement
      Marked enlargement
      Dilated tortuous veins
      Specific symptoms
      Spinal ischaemia due to vascular steal
      Treatment
      Surgery
      Endovascular ± Surgery
      Endovascular + surgery
      Oblietration rate
      93%
      71%
spinal intradural fistula
spinal intradural fistula
spinal intradural fistula

Standard anteroposterior spine angiograms

  • Intradural ventral AVFs: midline fistulous pouch
  • Intradural dorsal AVFs: lateral fistulous pouch

Aetiology

Radiology

A close-up of a spine AI-generated content may be incorrect.
A close-up of a mri scan AI-generated content may be incorrect.

Clinical presentation (Gross 2013)

  • Ischaemic myelopathy (93%)
    • Similar to dural fistula
    • Due to venous congestion
      • Similar to those with intradural dorsal fistulas.
      • Open into spinal cord veins, which often leads to the kind of global venous hypertension
      • Conus symptoms
        • Pain,
        • Progressive myelopathy,
        • Bowel/bladder/sexual dysfunction,
        • Saddle anesthesia
        • Sensory issues
  • Haemorrhage (32%)
    • More common than intradural dorsal type AVF because
      • Intradural fistulas are usually much higher flow lesions than dural fistulas, particularly the complex kind.
      • The arteries involved are not located in the relatively tough dura.
    • Both spinal subarachnoid hemorrhage and intraparenchymal (intramedullary) cord hemorrhage (hematomyelia)
      • We have an extremely low threshold for performing a spinal angiogram for any intradural hemorrhage, subarachnoid or intramedullary.
    • Causes
      • Initial: Sudden, severe back pain (“worst back pain of life”).
      • Later: weakness, sensory deficit, paralysis, and/or loss of bladder/bowel function usually follow in the next minutes (at which point pain, tragically, improves).
      • Exact nature of symptoms of course depends on the location and amount of bleeding.
    • Location
      • Cervical spine: extend into cranium causing SAH
        • 10% of Angio negative brain SAH will have Ventral intradural AVF

Treatment

  • Generally Microsurgical ± endovascular treatment
    • Type A
      • Microsurgical ± endovascular treatment
    • Type B
      • Microsurgical ± endovascular treatment
    • Type C
      • Endovascular treatment as hypertrophied feeding arteries facilitate navigation.
  • Radiosurgery
    • No much data to support it
  • Endovascular treatment
    • Aim
      • To close the actual fistula point,
        • While sparing as whatever necessary adjacent arterial and venous angioarchitecture exists.
        • Unless the fistula point is completely closed, the fistula will recur in a predictable sequence of clinical improvement, followed by re-appearance of symptoms as collaterals reconstitute the shunt.
    • Liquid embolic agent
      • nBCA
      • Onyx.
    • The venous “safety” question is important.
      • Spinal dural fistula venous safety is represented by the length of the bridging vein paralleling the length of the nerve roots, even though these veins are not supposed to be, strictly speaking according to Lasjaunias and Krings, “radicular”.
        • Longer in the lumbosacral spine, and quite short in the mid-thoracic segments
      • For the pial fistula, the venous safety is usually short
        • The fistula empties essentially directly into cord surface veins, and their integrity is critical to physiologic drainage of the spinal cord.
        • Embolizing these veins actually makes the situation worse, similar to early surgical results of venous stripping before the true pathoanatomy of the spinal dural fistula was recognised.
        • So the key is usually to take some vein (enough to make sure the glue sets in the fistula itself), but not too much.
          • From a personal perspective, I think its important to appreciate that all embolisation, even in the best of flow arrest circumstances, has a sizeable component of unpredictability.
          • The final success is only enhanced by considering of how the embolization might not go according to the plan.
          • Much of course depends on the exact angioarchitecture of the fistula.

Outcome

  • Obliteration rate 82% (Microsurgical ± endovascular treatment)
    • Type A 93%
    • Type B
    • Type C 71%