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Information

 Nervous System Disorders

= AVF

= abnormal communication between artery + vein resulting in tremendous amount of flow due to high pressure gradient → enlargement + elongation of draining veins; NO nidus

Cause:

  1. Vessel laceration (delay between trauma + clinical manifestation ← delayed lysis of hematoma surrounding arterial laceration)
  2. Angiodysplasia: fibromuscular disease, neurofibromatosis, Ehlers-Danlos syndrome
  3. Congenital arteriovenous fistula

Location:

  1. carotid-cavernous sinus fistula (most common)
  2. vertebral artery fistula
  3. external carotid artery fistula (rare)

Carotid-Cavernous Sinus Fistula  !!navigator!!

= abnormal communication between veins of cavernous sinus and ≥1 branches of internal / external carotid artery

  1. Direct shunt = direct communication between cavernous segment of ICA + cavernous sinus
    Etiology:
    1. Trauma: laceration of ICA within cavernous sinus
      1. usually due to basal skull fracture (cavernous ICA + small cavernous branches fixed to dura)
      2. penetrating trauma
      3. surgery
    2. Spontaneous: rupture of an intracavernous ICA aneurysm (in atherosclerosis, Ehlers-Danlos syndrome, osteogenesis imperfecta, pseudoxanthoma elasticum)
    3. Dural sinus thrombosis

    Age: any
    • classic triad:
      • pulsatile exophthalmos, conjunctival chemosis / edema
      • persistent auscultatory orbital bruit
    • restricted extraocular movement
    • decrease in vision ← increase in intraocular pressure (50%) / cranial nerve deficits = indication for EMERGENT TREATMENT
  2. Indirect shunt = communication between dural branch of ICA / ECA + cavernous sinus
    Age: 40–60 years; M <F
    Etiology: atherosclerosis
    • proptosis, loss of vision
    • ± visualization of feeding dural branches of ECA / ICA

Route of drainage:

  1. superior ophthalmic vein (common)
  2. contralateral cavernous sinus
  3. petrosal sinus
  4. cortical veins (rare)
  • dilatation + tortuosity of ipsilateral superior ophthalmic vein, facial veins, internal jugular vein
  • enlargement of dural venous sinuses ← increased venous flow + pressure
  • enlarged edematous extraocular muscles
  • focal asymmetric / diffuse enlargement of cavernous sinus
  • occasionally sellar erosion / enlargement
  • enlargement of superior orbital fissure (in chronic phase)
  • stretching of optic nerve
  • proptosis
  • subchoroidal effusion

US:

  • arterial flow in cavernous sinus + superior ophthalmic vein

CECT:

  • early opacification of cavernous sinus

MR:

  • flow voids in cavernous sinus

Angio:

  • ipsilateral ICA contrast injection shows wall of ICA to be incomplete
  • contralateral ICA contrast injection + compression of involved ICA
  • early opacification of veins of cavernous sinus
  • retrograde flow through dilated superior ophthalmic vein

Rx: transvenous / transarterial coil ablation ± stent placement; latex / silicone balloon detached inside cavernous sinus to plug laceration (→ ocular signs resolve within 7–10 days with successful treatment)

DDx: cavernous sinus thrombosis, enhancing cavernous sinus mass (meningioma, metastasis)

Dural AV Fistula  !!navigator!!

Arterial supply: artery normally feeding meninges (meningeal artery) / bone / muscles

Draining vein: venules within wall of dural sinus / cortical vein

Cause: dural sinus thrombosis → collateral revascularization

Prevalence: 10–15% of intracranial AV shunts

Peak age: 20–40 years; M=F

  • pulsatile tinnitus

Borden classification:

  • benign fistula (Borden type 1) → no cortical venous reflux → no neurologic deficits
  • malignant fistula (Borden type 2 & 3) → with cortical venous reflux
    • intracranial hemorrhage, seizure, dementia
    • focal neurologic symptoms due to venous congestion / rupture of venous pouches; altered consciousness

Location: cavernous sinus (20–40%), transverse / sigmoid sinus (20–60%), tentorium (12–14%), superior sagittal sinus (8%), anterior fossa (2–3%)

CECT:

  • multiple small vessels within wall of thrombosed / partially recanalized stenotic dural venous sinus
  • prominent feeding meningeal artery:
    1. ECA → dural / transosseous branch
    2. ICA / vertebral artery → tentorial / dural branch
  • enlarged draining veins
  • dilated transcalvarial channels ← transosseous feeding artery

MR:

  • dilated cortical veins (= pseudophlebitic pattern):
    • abnormal enhancing tubular structures
    • flow voids within cortical sulci
  • NO true nidus within brain parenchyma

Rx: observation, embolization, surgical resection

DDx: dural venous sinus thrombosis with prominent collaterals, pial AV malformation, pial AV fistula

Pial AV Fistula  !!navigator!!

= often high-flow lesions with direct fistulous communication between a pial artery + a vein WITHOUT intervening nidus

Arterial supply: enlarged pial artery

Draining vein: enlarged draining vein / capillary bed

Prevalence: 5% of all brain AVMs

Associated with: hereditary hemorrhagic telangiectasia (frequent)

Location: brain surface

Cause: trauma, genetically dysregulated angiogenesis

  • dilated vessels of brain surface (from MCA, ACA, PCA)
  • asymmetric dilatation of pial feeder artery
  • dilated often (serpentine) varicose draining vein
  • ± dilated venous pouches outside brain parenchyma
  • NO nidus / classic intraparenchymal tangle of vessels
  • ± spontaneous intracranial hemorrhage

Rx: embolization of draining vein at fistula

DDx: AV malformation, dural AV fistula, vein of Galen malformation

 Outline